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Dissertations / Theses on the topic 'Polymer ageing'

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Published: 10 February 2023

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1

Bose, Sonia Manjusri. "Computer simulation modelling of polymer ageing." Thesis, University of Surrey, 2002. http://epubs.surrey.ac.uk/843495/.

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Detailed information of the underlying mechanisms of macromolecular disintegration processes is not always fully available from lab-based experiments and GPC. A powerful computer simulation technique was thus indispensable in this respect whilst saving time, labour and expense. This project aims to develop an interactive computer program to capture the behaviour of a complex reactor and offer the following functionality: mathematical calculations, graph/chart generation, processing simulation-experiment pertaining to user-given scission and environmental characteristics, data saving and re-loading etc, Windows-style menu-driven interfaces provide templates for easy implementation of complex mathematical algorithms -a new simulation technique (Slider interfaces) presented in the thesis, based on cellulose-ageing study in electrical transformers (Heywood, 2000). A novel statistical concept was introduced to significantly improve real-tune performance of mathematical calculations to simulate polymer chain fragmentation phenomena, enabling transformation of the simple iterative to a semi-iterative and instant calculation algorithm. Three new mathematical functions were constructed - (a) Monte Carlo Dynamic (Slider), (b) Algebraic Exact, (c) Markov Statistical models, initially using an arbitrary time scale for degradation. Real-time simulation was developed using three time model variants that included the interpretation of deviations in the order reaction rate from linearity to an exponential type function. The above transformation enhanced reproducibility and accuracy of degraded MWD curve sampling whilst then- graphical display & clarity via 'Cubic B-Spline' smoothing-algorithm. Complex models were created from a ranking ensemble of single scission mechanisms, structured with levels of probability constructs to effectively simulate GPC-like curve-deformities and side-shifts. The simulation results provided new information in the following key areas: the temporal shift patterns of MWD/PCLD under different ageing conditions graphical comparisons between simulated and observed Idnetic and scission parameters. the dominant types of scission strategy at different reactor conditions, the dependence of reaction behaviour on the polymer structural order. An alternative way of predicting life expectancy of an ageing polymer via relating time- temperature to the magnitude of intermediate MWD curve shifts that is independent on DP. The latter is an average value and subjected to errors. An equation was derived for this. Introduction of a binary tree "death time" algorithm for calculation of the life expectancy of different categories of polymer chain species. Non-iterative techniques developed here opens up new avenues of further research. The developed algorithms and computer program may provide ample scope for investigating the ageing of other industrially important polymers and can be utilised in other areas of polymer research with little modification where probability distribution is sought.
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2

Elliott, Susan. "The physical ageing of homopolymers and blends." Thesis, Heriot-Watt University, 1990. http://hdl.handle.net/10399/888.

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3

Lee, Yuen-Pen. "Electrically and thermally activated ageing mechanisms in metallised polymer film capacitors." Thesis, Loughborough University, 2001. https://dspace.lboro.ac.uk/2134/33870.

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This dissertation describes a combined computational and experimental study to understand the fundamental electrostatic, thermal, electromagnetic, and discharge related processes during the ageing of metallised polymer film capacitors. In the event of internal breakdowns, these capacitors are capable of "self-healing" through a controlled isolation of defects on the electrode surfaces by mosaic patterning the electrode. The objective of this project is to develop viable computer models to unravel electrothermally activated ageing processes in capacitors. To provide the necessary validation to any capacitor models developed, our work is supported by comprehensive experiments including industrial standard accelerated life tests and associated breakdown damage analyses of tested capacitors.
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4

Liu, Ning. "Space charge characteristics in polymer materials and their relation with ageing." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/417276/.

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Space charge formation in polymeric materials can cause serious concerns for design engineers as the electric field may severely be distorted, leading to part of the material being overstressed. This may give rise to accelerated material degradation and possibly premature failure in the worst conditions. As space charge dynamics in polymeric materials can be directly related to the changes in their composition, structure and morphology, a quantitative model is highly desirable for a better understanding of charge injection, trapping and detrapping in the polymeric materials. This dissertation reviews some well-known ageing models of insulating materials and shows their related derivation procedures. Most of these models treated ageing phenomenon as a chemical kinetics process but explained it using different approaches microscopically. Moreover, these models hold different perspectives on space charge effect on ageing. According to Crine’s model and Lewis’ model, space charge is just one of the consequences of material degradation whereas in the model established by Dissado-Montanari-Mazzanti, it is intended to prove that space charge can also act as a cause of ageing. In the present research, the space charge characteristics of both normal and gamma-irradiated low density polyethylene (LDPE) films during voltage-off periods have been investigated by PEA technique. Irradiation treatment can alter the physical structures of materials and bring chemical changes into normal samples. By analyzing those parameters estimated by Chen’s trapping/detrapping model, it shows the increment in trap sites and changes in trap depths, indicating that chemical reactions brought by irradiation have some changes in trapping characteristics of LDPE. However, there are some drawbacks in the previous trapping/detrapping model. By considering Schottky injection process and a modified Pool-Frenkel conduction mechanism, an improved trapping/detrapping model is established based on Chen’s model. Such model can not only estimate the trapping parameters of polymeric materials like previous models but also evaluate some new parameters like mobile charge escape rate coefficient and injection barrier for both electrons and holes. By using such a model, trapping parameters of aged samples under nine different ageing conditions are estimated. Moreover, breakdown tests were performed on these samples. An increment in breakdown strength can be found for samples from the early stage of ageing. This can be explained by the surface oxidation process which concentrates the charges near the both electrodes and therefore reduce the field between metal-insulator interface. When the ageing condition reach certain circumstance (applied field and temperature sufficiently high), the breakdown strength begin to decrease due the generation of traps in the sample bulk. With the experimental data of dc breakdown tests for different aged samples, a new model to depict the relationship between breakdown strength and ageing conditions (electric field, temperature and ageing time) has been built based on Simoni’s model. Such a new model mimic the initial rise of the breakdown strength by introducing an inverse reaction rate during the ageing. Moreover, through the implementation of such a model, the electron trap density can be used to quantitatively reflect the stage of ageing. Several XLPE extruded cable sections (12, 11, 10 and 8-year) retired from HVAC service are peeled into films by using the microtome. Preliminary experimental works were done by using the 10-year cable section: the heterocharges accumulation near both electrodes can be observed. To see homocharge injection, degas treatment is thereby required to eliminate the byproducts, which can give rise to ionic dissociation process inside the sample. Thereafter, based on the improved trapping/detrapping model, trapping parameters of the XLPE peelings are found for 12, 11 and 8-year operated cable sections. The estimated injection barrier, trap density and overall trap depth can be clearly related to the dc breakdown performance of XLPE samples. Moreover, from the estimated trapping parameters and the breakdown tests, they both indicate that the inner layer is most seriously aged part across the radial direction of the cable section. The threshold field (dc) of charge injection can be evaluated through three approaches for LDPE materials. Subtraction method on voltage-on measurement data and direct measurement on charges with multiple voltage-off tests can both give values of the threshold field. And the subtraction method is more sensitive way to obtain a relatively lower threshold field at 8 kV/mm. Another method taking account of maximum peak heights at both electrodes is not suitable to measure threshold field for total charge injection but can give an inception field of injection respectively for positive or negative charges. Taking advantage of plasma technology using gas CF4, fluorination treatments are performed on LDPE samples to produce fluorinated samples at two different discharge voltage levels and two different exposure times. For both normal and fluorinated LDPE samples, the space charge measurements are performed. The results indicate that the injected homocharges can be effectively suppressed with fluorination process but the heterocharges which come from ionization of the lower molecular weight specifies become prominent in the sample. The sufficient fluorination on normal LDPE samples can lower the dc conductivity but when the fluorination is not enough, the heterocharges can lead to even higher dc conductivity than the original one.
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5

Zhang, Xin. "Etude du vieillissement thermique de revêtements de peinture sur plaque par réflectométrie ultrasonore." Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20234.

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La recherche de critères de vieillissement des revêtements de protection sur le long terme est nécessaire dans de nombreuses configurations industrielles. Ce travail présente l'étude de l'évolution de l'élasticité de revêtements de peinture sur plaque métallique par réflectométrie ultrasonore pour détecter de façon non destructive l'endommagement induit lors de tests de vieillissement thermique accéléré. La modélisation du pouvoir réflecteur permet d'identifier, dans une certaine gamme de fréquence, un mode particulier dont la valeur de l'angle critique est préférentiellement sensible à la rigidité de la couche en bon accord avec les tests réalisés sur des revêtements de 100µm de peinture sur plaque d'acier. Cette méthode est appliquée sur des échantillons étuvés à 80°C et 110°C durant 4000 heures. En fonction de la température, la mesure quotidienne de la position de cet angle critique permet de suivre le temps nécessaire au séchage complet des revêtements suite à l'évaporation du solvant. Au-delà, les variations de cette position angulaire indiquent, pour les modules élastiques de la peinture, une légère augmentation de moins de 2%. L'altération de la structure chimique détectée par mesures de température de transition vitreuse et de concentration de certains marqueurs (FTIR) se traduit donc par des modifications faibles d'élasticité nécessitant une résolution angulaire inférieure à 0,1°. Pour mieux différencier la rigidité de ces échantillons suite au vieillissement thermique, la sensibilité nécessaire est obtenue en réalisant une excursion en température autour de l'ambiante de quelques °C durant les mesures de réflectométrie
The determination of paint coating's ageing criteria after long term service is necessary in many industrial configurations. In this work, we have studied by ultrasonic reflectometry the evolution of the elasticity of paint coated on a metallic plate in order to detect in a non destructive way the damage induced by thermal accelerated ageing tests. The simulation of the reflection coefficient identifies a particular mode whose critical angle is preferentially sensitive to the elasticity of the paint layer in a particular range of frequency. This result is in agreement with experimental tests performed on 100 µm thick paint coated on a steel plate. These samples are heated at 80°C and 110°C during 4000 hours. The everyday measurement of the evolution of the critical angle allows the identification of the time necessary to reach the complete drying of the paint coating. This parameter depends on the heating temperature. The total variations of these critical angular positions indicate a small increase less than 2% of the paint's elasticity moduli. In parallel, the change of the chemical structure is detected by the measurement of the glass transition temperature and the concentration of some markers identified by FTIR. This chemical change is linked to a small variation of elasticity implying an angular resolution less than 0.1°. For an easier differentiation of the rigidity of these thermally aged coatings, an enhanced sensibility is obtained by changing the temperature during the reflectometry measurements
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6

Pehlivan-Davis, Sebnem. "Polymer Electrolyte Membrane (PEM) fuel cell seals durability." Thesis, Loughborough University, 2016. https://dspace.lboro.ac.uk/2134/21749.

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Polymer electrolyte membrane fuel cell (PEMFC) stacks require sealing around the perimeter of the cells to prevent the gases inside the cell from leaking. Elastomeric materials are commonly used for this purpose. The overall performance and durability of the fuel cell is heavily dependent on the long-term stability of the gasket. In this study, the degradation of three elastomeric gasket materials (silicone rubber, commercial EPDM and a developed EPDM 2 compound) in an accelerated ageing environment was investigated. The change in properties and structure of a silicone rubber gasket caused by use in a real fuel cell was studied and compared to the changes in the same silicone rubber gasket material brought about by accelerated aging. The accelerated aging conditions were chosen to relate to the PEM fuel cell environment, but with more extreme conditions of elevated temperature (140°C) and greater acidity. Three accelerated ageing media were used. The first one was dilute sulphuric acid solution with the pH values of 1, 2 and 4. Secondly, Nafion® membrane suspended in water was used for accelerated ageing at a pH 3 to 4. Finally, diluted trifluoroacetic acid (TFA) solution of pH 3.3 was chosen. Weight change and the tensile properties of the aged gasket samples were measured. In addition, compression set behaviour of the elastomeric seal materials was investigated in order to evaluate their potential sealing performance in PEM fuel cells. The results showed that acid hydrolysis was the most likely mechanism of silicone rubber degradation and that similar degradation occurred under both real fuel cell and accelerated aging conditions. The effect of TFA solution on silicone rubber was more aggressive than sulphuric acid and Nafion® solutions with the same acidity (pH value) suggesting that TFA accelerated the acid hydrolysis of silicone rubber. In addition, acid ageing in all three acidic solutions caused visible surface damage and a significant decrease in tensile strength of the silicone rubber material, but did not significantly affect the EPDM materials. EPDM 2 compound had a desirable (low) compression set value which was similar to silicone rubber and much better than the commercial EPDM. It also showed a very good performance in the fuel cell test rig conforming that it a potential replacement for silicone rubber in PEMFCs.
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7

Fromageot, Camille. "Modification of biodegradable polymer films." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/131622/1/Camille_Fromageot_Thesis.pdf.

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This project aimed at tuning the photodegradability of a biodegradable polyester by employing a photosensitizing molecule, 2-oxepane-1,5-dione (OPD), as an additive mixed with commercial polymer and as a monomer to be copolymerized. Various processing techniques were employed, such as reactive extrusion, film blending or synthesis of polymers. The accelerated artificial ageing of modified polyesters revealed that OPD accelerated the rate of photodegradation of the polyester, with the differing mechanisms of degradation found for blends and copolymers providing scope for tuning the photodegradability of the polyester via alteration of the method of OPD incorporation.
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8

Cooper, Elizabeth Susan. "Application of polymer ageing models to cable geometry and time-to-failure distributions." Thesis, University of Leicester, 2002. http://hdl.handle.net/2381/9984.

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Polymer ageing models predict the working lifetime of polymeric insulation in terms of the electrical and thermal stresses to which it is subjected. Two such models are investigated in this thesis and are found to be mathematically similar even though they are based on different mechanisms for the way in which an electric field accelerates the ageing process. It is shown that both models can successfully fit characteristic time-to-failure data from ageing experiments involving thin films. A new method is developed to allow the ageing models to be applied to cable insulation, where the field and temperature are not spatially constant. This method is used to apply one of the models to characteristic lifetime data from experiments involving cables. The fits to data are found to be good, and resulting parameter values are used as the basis for a discussion of the possible effects of specimen volume on ageing. The distribution of failure times observed when thin films and cable insulation are aged at a given experimental condition has also been investigated. This has been carried out using distributions of the activation free energy of ageing within one of the ageing models. It is established that small changes in the minimum activation energy from specimen to specimen could be responsible for the observed failure statistics. Changes in the activation energy distributions with ageing condition suggest that ageing may involve conformational re-arrangements of chain segments in the crystalline-amorphous interface. This is in broad agreement with the conclusions of other workers.
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9

Jemmett, Peter A. "Investigation into the effects of ageing on the explosiveness of a polymer bonded explosive." Thesis, Cranfield University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421234.

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10

Zhao, Weijia. "Partial discharge ageing of polymer insulation under combined AC and DC stress at elevated temperatures." Thesis, University of Strathclyde, 2017. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=28507.

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Cable termination is the weakest part in any HV underground cable system, as defects may be left in the main insulation during the installation process. In HVDC systems, the converters produce the intended DC voltage for transmission but there may also be AC harmonics superimposed. The frequency of the AC harmonics could be in kHz range. The superimposed harmonics on the HVDC may have synergistic effects on cable insulation and may lead to further degradation in the cable insulation. In addition, for the sake of environmental protection, XLPE is no longer the suitable choice for underground cable insulation as it cannot be recycled. Thermoplastic material may be a candidate. There is little published information on the behaviour of thermoplastic materials under combined AC and DC voltages. In thermoplastic materials, HDPE film and PP film were selected as the target material to study in this project. As the properties of HDPE are similar to those of XLPE, the data obtained from HDPE was regarded as a bench-mark. It was decided to use the thermo-electrical stress to age the samples. For thermal stress, 90°C was chosen as the aging temperature for HDPE, while 90°C and 110°C were chosen for PP. For the electrical stress, AC & DC combined voltage was used to age the samples. DC voltage was 6 kV. The superimposed frequency of AC voltage was 1 kHz, 1.5 kHz, 2 kHz and 2.5 kHz. The AC/DC voltage ratio is from 10%, 30% and 50%. In this project, the effect of frequency and voltage ratio on HDPE and PP degradation under superimposed stresses was studied using the following approaches: Equivalent Phase Resolved Partial Discharge (PRPD) plots, Fourier Transform Infrared - Attenuated Total Reflection (FTIR-ATR) Spectroscopy and Dielectric Spectroscopy (DS) measurements were carried out. The performance of HDPE and PP were compared.
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11

Stoynov, Lou A. "System development and studies on utilization of concentrated solar beam radiation for polymer processing." Thesis, Queensland University of Technology, 2006. https://eprints.qut.edu.au/16196/1/Lou_Stoynov_Thesis.pdf.

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Various solar energy technologies are being developed to harness the available environmentally friendly and sustainable solar radiation. New ways of utilizing this "free" power for different energy consuming processes continue to be created. In this thesis, a multi-stage solar energy concentrating system has been developed and its feasibility as a radiation source for polymer processing has been explored. The solar energy concentrator (SEC) facility comprises a modified Cassegrainian configuration combined with auxiliary imaging and non-imaging optics, serving as an alternative energy source for polymer joining, ageing and adhesive curing. Modeling and improvement of various aspects of the operation and performance of the SEC facility have been implemented. Optical ray tracing models of the Cassegrainian concentrator with various conventional imaging components and nonimaging concentrators have been created to optimize the optical layout and system efficiency. On their basis, combined 3D ray tracing computer models integrated with the mechanical components have been developed to simulate the entire SEC facility and predict the image size, location and orientation. Additionally, the energy transfer, radiation absorption and heat generation and transfer in the irradiated polymer have been modeled in order to study the radiation-polymer interaction. One novel contribution of this research is the enhancement of the image forming concentrator with non-imaging cone-like concentrators (conical and compound parabolic concentrator (CPC)), utilizing their inherent disadvantage of excessive length. Compared to the refractive type means of transmitting concentrated solar radiation, the truncated cone and CPC concentrators have been found more efficient enhancing further the concentration and widening the utilized spectral range. The experimental studies have demonstrated that transparent and colored, similar and dissimilar polymers can be successfully joined using the SEC facility. The especially developed through-transmission technique removes the need to use a special absorbing medium of the radiant energy required by current advanced welding techniques. The tensile strengths of the joints achieved are comparable to those achieved for similar polymers with other advanced plastic joining methods. The results from the polymer ageing experiments have shown that ultraaccelerated exposure to concentrated sunlight can be performed with the SEC facility without introducing spurious failure mechanisms. Based on the preliminary investigation on adhesive curing utilizing concentrated solar radiation, it has been concluded that with carefully chosen light-curing adhesives solar radiation can be a useful radiation source for adhesive curing.
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12

Stoynov, Lou A. "System development and studies on utilization of concentrated solar beam radiation for polymer processing." Queensland University of Technology, 2006. http://eprints.qut.edu.au/16196/.

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Various solar energy technologies are being developed to harness the available environmentally friendly and sustainable solar radiation. New ways of utilizing this "free" power for different energy consuming processes continue to be created. In this thesis, a multi-stage solar energy concentrating system has been developed and its feasibility as a radiation source for polymer processing has been explored. The solar energy concentrator (SEC) facility comprises a modified Cassegrainian configuration combined with auxiliary imaging and non-imaging optics, serving as an alternative energy source for polymer joining, ageing and adhesive curing. Modeling and improvement of various aspects of the operation and performance of the SEC facility have been implemented. Optical ray tracing models of the Cassegrainian concentrator with various conventional imaging components and nonimaging concentrators have been created to optimize the optical layout and system efficiency. On their basis, combined 3D ray tracing computer models integrated with the mechanical components have been developed to simulate the entire SEC facility and predict the image size, location and orientation. Additionally, the energy transfer, radiation absorption and heat generation and transfer in the irradiated polymer have been modeled in order to study the radiation-polymer interaction. One novel contribution of this research is the enhancement of the image forming concentrator with non-imaging cone-like concentrators (conical and compound parabolic concentrator (CPC)), utilizing their inherent disadvantage of excessive length. Compared to the refractive type means of transmitting concentrated solar radiation, the truncated cone and CPC concentrators have been found more efficient enhancing further the concentration and widening the utilized spectral range. The experimental studies have demonstrated that transparent and colored, similar and dissimilar polymers can be successfully joined using the SEC facility. The especially developed through-transmission technique removes the need to use a special absorbing medium of the radiant energy required by current advanced welding techniques. The tensile strengths of the joints achieved are comparable to those achieved for similar polymers with other advanced plastic joining methods. The results from the polymer ageing experiments have shown that ultraaccelerated exposure to concentrated sunlight can be performed with the SEC facility without introducing spurious failure mechanisms. Based on the preliminary investigation on adhesive curing utilizing concentrated solar radiation, it has been concluded that with carefully chosen light-curing adhesives solar radiation can be a useful radiation source for adhesive curing.
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13

Pecora, Marina. "Development of a Cyclic Indentation Method for the Characterisation of Material Gradients in Polymers and Polymer Composites Due to Thermal Aging." Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2018. http://www.theses.fr/2018ESMA0011/document.

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Le marché des matériaux composites à matrice organique (CMO) pour la réalisation de pièces structurales "froides" (-55°C < T < Tamb) arrive à saturation et l’industrie aéronautique vise à utiliser les CMO tissés 3D dans les pièces structurales dites "chaudes" (50°C < T < 300°C) des avions (nacelles,turbomoteurs). Ces conditions environnementales peuvent entrainer des phénomènes de dégradation à long terme. L'action de l'environnement et la complexité de la microstructure peuvent conduire au développement de gradients de propriétés dans les matériaux. À haute température, la matrice polymère peut présenter un comportement complexe dépendant du temps. Il est donc nécessaire de mettre au point une technique expérimentale capable de caractériser le comportement du matériau en fonction du temps à l'échelle locale, pour saisir les gradients des propriétés. Ce travail propose la mise en place d'un essai cyclique d'indentation instrumentée pour répondre à ces questions.L'indentation instrumentée est une technique expérimentale qui a rencontrée un grand succès au cours des dernières années. Dans sa forme classique, développée pour les matériaux à comportement élasto-plastique, elle consiste à réaliser un seul cycle de charge/décharge pour en déduire la dureté du matériau et le module élastique d’indentation. Cette analyse n'est pas appropriée pour les matériaux présentant un comportement dépendant du temps, ce qui nécessite de développer une nouvelle méthode optimisée pour les matériaux polymères. Les méthodes d'indentation pour les matériaux polymères proposées dans la littérature (fluage, dynamique), sont limitées à certaines charges. L'essai cyclique d'indentation proposé dans ce travail vise à mettre en évidence la complexité du comportement du polymère. Il est dérivé des essais cycliques macroscopiques et emploi une méthode d’analyse similaire. La technique est développée sur un polymère thermoplastique, le PEHD, pour lequel la réponse cyclique macroscopique en traction et cisaillement est connue. En suivant l’évolution au cours du temps des principaux indicateurs du comportement cyclique (le module d'indentation,l’aire de la boucle d'hystérésis et l'accumulation du déplacement) pour différentes fréquences, il est possible de mettre en évidence la réponse du matériau et d'effectuer une comparaison qualitative avec le comportement macroscopique. Le protocole d'indentation cyclique est ensuite utilisé pour étudier les gradients de propriétés dans la résine époxy thermodurcissable PR520 soumise à un vieillissement thermique à 150°C sous air à pression atmosphérique (jusqu'à 1000h), sous 2 bar d’O2et de N2 (pour 400h). Il est montré que la cinétique d’évolution du module d'indentation et du déplacement n'est pas affectée par le vieillissement. Cependant, leurs valeurs absolues varient de la surface au cœur du polymère, ce qui indique la présence de gradients. L'hystérésis du premier cycle est différente à travers le gradient, mais à partir du deuxième cycle, l'hystérésis est similaire pour toutes les conditions de vieillissement et les distances de la surface exposée. Les résultats obtenus sur des échantillons vieillis sous 2 bar d’O2 et de N2 permettent de conclure que la cinétique de vieillissement n'est pas de la pure thermo-oxydation. La méthode d'indentation cyclique est ensuite appliquée pour caractériser le comportement de la matrice époxy PR520 dans un composite tissé 3D,à l'état vierge et vieilli à 150°C sous air à pression atmosphérique. L'étude du composite à l'état vierge révèle que le comportement de la matrice polymère à proximité de la surface externe est différent de celui situé dans les zones internes du composite et du polymère pur. La comparaison entre le polymère pur et la matrice à l’état vieilli montre que les gradients de propriétés induits par l'environnement sont similaires
The market of organic matrix composite (OMC) materials for the realisation of “cold” (-55°C < T < RT) structural parts is going towards saturation and aircraft manufacturers foresee the employment of 3D reinforced OMC in “warm” (50°C < T < 300°C) aircraft structural parts (nacelles, turbo-engines). These environmental conditions may lead to degradation phenomena over long time. The action of environment and the complexity of the material microstructure may lead to the development of material property gradients. At high temperature, the organic polymer matrix may exhibit complex time-dependent behaviour. Therefore, there is a need to develop an experimental technique able to characterise the material behaviour at local scale and to capture material gradients and time-dependent behaviour. The present work proposes the development of a cyclic instrumented indentation test to tackle all these issues. Instrumented indentation is a popular testing technique: its basic version, appropriate for elasto-plastic materials, includes the realisation of a single loading/unloading test, the measurement of the material hardness through the analysis of the indentation print, and the analysis of the unloading curve based on the assumption of elastic unloading behaviour to obtain the indentation modulus. This analysis is inappropriate for materials exhibiting time-dependent behaviour, which leads to the need of a new method optimized for polymer materials.Several indentation methods are available for polymer materials (indentation creep, nanoDMA), but are limited to some specific loadings. The instrumented indentation cyclic test proposed in this work tries to emphasize the whole complexity of the polymer behaviour, is inspired by macroscopic cyclic tests and is analysed similarly. The technique is first set up and developed by testing a HDPE thermoplastic polymer, for which the response to macroscopic cyclic tension and shear loading isknown. By following, at different frequencies, the evolution with time (with cycles) of the principal indicators of the cyclic behaviour – that is, the indentation modulus, the hysteresis loop area and the indentation depth accumulation - it is possible to highlight the time-dependent response of the material and to perform a proper – though qualitative - comparison with the macroscopic behaviour. The cyclic indentation protocol is then employed to study the material gradients in a thermoset PR520epoxy resin subjected to thermal aging at 150°C under air at atmospheric pressure (up to 1000h), 2 barO2 (for 400h) and N2. It is shown that the evolution with cycles of the indentation modulus and the cyclic creep is not affected by thermal aging. However, their absolute values vary from the surface to the core of polymer indicating the presence of gradients. The hysteresis of the first cycle is different through the gradient: from the second cycle, however, the hysteresis is similar for all aging conditions and distances from the exposed surface. Moreover, the time-dependent behaviour stays unchanged. Results from samples aged under 2 bar O2 and 2 bar N2 allow to conclude that the aging kinetics is not related to pure thermo-oxidation phenomena. The cyclic indentation method is finally applied to characterise the behaviour of PR520 epoxy matrix within a 3D interlock textile composite, in its virgin state and thermally aged at 150°C under air at atmospheric pressure (up to 1000h). The polymer inlarge matrix pockets between the fibrous reinforcements is studied in this work, so the constrainingeffect coming from the reinforcement is negligible. The study of the composite in virgin state revealsthat the behaviour of polymer matrix close to the external surface is different from that located ininternal zones of the composite and from the neat polymer. The comparison between the thermallyaged neat polymer and matrix in internal zones of the composite shows that the environment-inducedproperty gradients are similar
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Gomes, Hastenreiter Lara Lopes. "Biodegradation and ageing of bio-based thermosetting resins from lactic acid." Thesis, Högskolan i Borås, Akademin för textil, teknik och ekonomi, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-23320.

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The need for replacing petroleum-based polymers has been increasing and bio-based polymers prove to be a suitable solution. The aim of this thesis was to synthesize bio-based resins with different chemical architectures to evaluate the effect of the structure on the properties and on their response to ageing and biodegradation. For this, three different bio-based thermoset resins have been synthesised by reacting one of three distinct core-molecules with lactic acid. The options of core-molecules chosen for this work were ethylene glycol, glycerol and pentaerythritol. Lactic acid was first reacted with a core-molecule by direct condensation, the resulting branched molecule was then end-functionalized with methacrylic anhydride. The amount of moles of lactic acid varied according to which core-molecule it was reacted with, but the chain length (n) was always maintained as three. Part of the samples were characterised by Fourier-transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and tensile test. DSC and TGA were used for determining the thermal behaviour. FT-IR was used to verify the first and second stage of the reaction and to ascertain the occurrence of the crosslinking reaction. Tensile test was done for investigation of mechanical properties. The ageing and biodegradation tests are useful to ascertain the material possible applications. Therefore, the samples that went through the process of ageing or biodegradation were also characterised in the end of the procedures to further check the effect of those processes on the specimens. The test results indicated that the PENTA/LA cured resin was the most stable thermally. The cured resin’s mechanical properties were similar to each other, so there was no comparison to make in this area. The samples proved to be affected by the biodegradation and the ageing processes, both in visual and structural aspects.
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15

Guillermin, David. "Le rôle des matériaux hybrides à base d'argiles dans la protection des œuvres d'art." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS288/document.

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Le travail de cette thèse s’intéresse à la stabilisation de plusieurs pigments hybrides.Une première partie traite de pigment obtenu à l’aide de l’acide carminique et de la montmorillonite, une argile commune. Un procédé d’inversion de la charge de surface de l’argile avec un polymère cationique, ou l’utilisation d’argiles modifiées par des polycations de Titane et d’Aluminium, permettent l’élaboration du pigment. La résistance des pigments à la photodégradation est alors testée. Les techniques couplées de RMN, DRX, FTIR et d’EPR permettent d’éclairer l’agencement des molécules organiques sur la surface minérale, et également de suivre le processus de dégradation du colorant.La description de pigments hybrides obtenus à l’aide d’un spiropyrane vient compléter l’étude. Le composé, qui joue le rôle de colorant organique, est ajouté à différentes matrices minérales : l’argile, modifiée ou non, ainsi que la co-précipitation avec des organo-silanes. Ces synthèses permettent d’observer la variété de couleur obtenus en mélangeant un même colorant avec plusieurs matrices de nature différente
The work of this thesis focuses on the stabilization of several hybrid pigments.The first part deals with pigment obtained with carminic acid and montmorillonite, a common clay. A method of reversing the surface charge of the clay with a cationic polymer, or the use of clays modified with titanium and aluminum polycations, allows the elaboration of the pigment. The resistance of the pigments to photodegradation is then tested. Coupled NMR, DRX, FTIR and EPR techniques help to illuminate the arrangement of organic molecules on the mineral surface, and also to follow the dye degradation process.The description of hybrid pigments obtained using a spiropyran completes the study. The compound, which plays the role of organic dye, is added to different mineral matrices: clay, modified or not, and co-precipitation with organosilanes. These syntheses make it possible to observe the variety of color obtained by mixing the same dye with several matrices of different nature
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16

Jankowski, £ukasz. "Modelling and simulation of light propagation in non-aged and aged step-index polymer optical fibres." Phd thesis, Universität Potsdam, 2004. http://opus.kobv.de/ubp/volltexte/2005/173/.

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Kunststofflichtwellenleiter (POFs) stellen ein verhältnismäßig neues Medium zur optische Datenkommunikation über kurzen Strecken dar. Während ihrer Einsatzdauer unterliegen POFs unterschiedlichen Arten von Umweltbeanspruchungen, hauptsächlich durch hohe Temperatur, hohe Feuchtigkeit und mechanischen Belastungen. Zahlreiche experimentelle Forschungen beschäftigten sich mit der standardisierten Prüfung der Zuverlässigkeit von im Handel erhältlichen Fasern. Jedoch gab es bisher wenig Erfolg bei der Bemühung, zwei grundlegende optische Erscheinungen, Absorption und Streuung, die die Lichtausbreitung in Fasern stark beeinflussen, zu verstehen und praktisch zu modellieren: Diese beiden Effekte beschreiben nicht nur die Qualität neuer Fasern, sondern sie werden auch stark durch die Alterungsprozess beeinflusst.

Der Hauptzweck dieser Doktorarbeit war es, ein praktisch verwendbares und theoretisch gut fundiertes Modell der Lichtausbreitung in nicht gealterten und gealterten POFs zu entwickeln und es durch optische Experimente zu verifizieren. Dabei wurden anwendungsorientierte Aspekte mit theoretischer POF-Modellierung kombiniert. Die Arbeit enthält die erste bekannte Anwendung der Wellenanalyse zur Untersuchung der winkelabhängigen Eigenschaften der Streuung in Lichtwellenleitern.

Für die praktischen Experimente wurden mehrere POF-Proben unterschiedlicher Hersteller künstlich gealtert, indem sie bis 4500 Stunden bei 100 °C gelagert wurden (ohne Feuchtekontrolle). Die Parameter der jeweiligen Simulationen wurden mittels einer systematischen Optimierung an die gemessen optischen Eigenschaften der gealterten Proben angeglichen. Die Resultate deuten an, dass der Übertragungsverlust der gealterten Fasern in den ersten Tagen und Wochen der Alterung am stärksten durch eine wesentliche physikalische Verschlechterung der Kern-Mantel-Grenzfläche verursacht wird. Chemische Effekte des Alterungsprozesses scheinen im Faserkernmaterial zuerst nach einigen Monaten aufzutreten.
This thesis discusses theoretical and practical aspects of modelling of light propagation in non-aged and aged step-index polymer optical fibres (POFs). Special attention has been paid in describing optical characteristics of non-ideal fibres, scattering and attenuation, and in combining application-oriented and theoretical approaches. The precedence has been given to practical issues, but much effort has been also spent on the theoretical analysis of basic mechanisms governing light propagation in cylindrical waveguides.

As a result a practically usable general POF model based on the raytracing approach has been developed and implemented. A systematic numerical optimisation of its parameters has been performed to obtain the best fit between simulated and measured optical characteristics of numerous non-aged and aged fibre samples. The model was verified by providing good agreement, especially for the non-aged fibres. The relations found between aging time and optimal values of model parameters contribute to a better understanding of the aging mechanisms of POFs.

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17

Lansing, Eric. "Verification of Polymeric Material Change in the Air Intake System." Thesis, KTH, Skolan för kemivetenskap (CHE), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-213012.

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The air intake manifold is an integral part of modern internal combustion engines. Currently manufactured in glass fibre reinforced PA66, inquiries have been raised regarding a change of material to glass fibre reinforced PP. A new engine project is the purpose for which this proposed material is evaluated. The thermochemical environment in the air intake system puts high demands on the material. Ageing treatments and tensile testing was conducted on samples of the new material, as well as on the currently used PA66 to evaluate mechanical response of each material to treatments made to simulate the air intake environment. Furthermore, understanding of the chemical setup is lacking and needs to be studied. Experiments was performed to study the chemistry of the intake environment. Results indicated that PP can retain sufficient mechanical rigidity and strength when subjected to parameters made to simulate the air intake. Moreover, results regarding the chemical environment in the air intake system provided limited information.
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18

Dominguez, Sébastien. "Relation structure/propriétés de polymères et mélanges thermoplastiques thermostables - Applications Aéronautiques Hautes Températures." Thesis, Pau, 2013. http://www.theses.fr/2013PAUU3031/document.

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Nos travaux sont consacrés à la fabrication, à la mise en œuvre et aux caractérisations de mélanges de polymères thermoplastiques thermostables destinés à des applications aéronautiques hautes températures. Le Poly(éther cétone cétone) PEKK, polymère semi-cristallin, a été choisi pour sa température de transition vitreuse (Tg) et son point de fusion (Tf) élevés. Les polyimides amorphes utilisés pour leur Tg élevée, sont le Poly(éther imide) PEI et le (polyimide) PI. Le but de ces mélanges est d’augmenter la Tg du PEKK, sans augmenter sa température de fusion. Ces travaux ont abouti à la caractérisation thermique, mécanique et rhéologique de chacun des polymères purs ainsi qu’à la définition d’un protocole de fabrication des mélanges. Les propriétés des mélanges ont alors été caractérisées par analyses thermomécaniques, par balayage calorimétrique différentiel et par des essais de traction afin de faire ressortir les meilleurs candidats pour les applications visées. Les modèles empiriques classiques de variation de la Tg prennent en compte seulement la composition des mélanges. Dans ce travail, nous proposons de corriger ceux-ci par la prise en compte de la variation du taux de cristallinité qui influe sur la composition de la phase amorphe et ainsi permettre une prévision plus fine de ce paramètre. La tenue au vieillissement à court terme des différents polymères dans un fluide aéronautique a aussi été abordée, et a montré que le PEKK a un effet protecteur sur les mélanges
This PhD work presents the fabrication, processing and characterizations of thermoplastic thermostable polymer blends. It aims at finding new materials useable at high temperatures for aeronautical applications. Poly(ether ketone ketone), PEKK, a semi-crystalline polymer, has been chosen for its high glass transition temperature (Tg) and high melting point (Tf). Amorphous polyimides, that have been used for their high Tg, are Poly(ether imide), PEI, and Polyimide, PI. The aim of these blends is to increase the Tg of the PEKK without increasing its Tf. We have measured the thermal, mechanical and rheological properties of each neat polymer and the processing conditions of the blends have been defined. The properties of the blends have been characterized by thermomechanical analyses, differential scanning calorimetry and tensile tests to focus on the better candidates for the aimed applications. The classical empirical models of the Tg composition dependence take only into account the blends composition. We propose to correct them taking into account the crystallinity level, that affects the blends composition and predict a better prediction of the Tg . The short term ageing of these polymer blends specimens in a commonly used aeronautic fluid has also been studied, and showed the protection effect of the PEKK polymer in the blends
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19

Surmann, Ralf. "Etude du vieillissement des géomembranes : mécanismes, essais et caractérisation." Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10208.

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La geomembrane est la barriere active de l'etancheite du site d'enfouissement technique. Apres le remplissage des casiers de dechets et apres la couverture, une reparation de defauts de la geomembrane en fond de casier est pratiquement impossible, d'ou la necessite d'etudier la bonne tenue a court et long terme des geomembranes. L'auteur a mis en place des dispositifs experimentaux de vieillissement en laboratoire et in situ qui permettent de simuler une exposition des geomembranes comparable a celle qui existe au fond des centres d'enfouissement technique. Le vieillissement a ete realise sur une duree entre 1 et 2 ans (et plus) suivant le materiau etudie: pehd, le pvc et le bitume. Le lixiviat est le milieu d'immersion des geomembranes. Il est donc etudie lors de cette etude et des liquides d'immersion de synthese pour des essais reproductibles en laboratoire sont proposes. Des analyses mecaniques, physico-chimiques et purement chimiques sont necessaires pour caracteriser les geomembranes et leur vieillissement. Chaque materiau necessite des analyses et un ensemble de techniques specifiques qui ont ete selectionnees au cours de ce travail. Les analyses, les plus importantes pour chaque materiau, sont effectuees sur les geomembranes temoins (non-vieillies) et vieillies. Les buts de ces recherches analytiques sont la mise au point d'un programme analytique pour chaque type de geomembrane et une meilleure connaissance des mecanismes de vieillissement des geomembranes dans le site d'enfouissement technique
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20

Rahme, Roland. "Adhérence et durabilité en milieu sec et humide de multi matériaux acier/polymère thermoplastique." Thesis, Lyon 1, 2010. http://www.theses.fr/2010LYO10301.

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L'objectif de notre travail est de développer un composite acier/polymère épais qui vise à apporter l'allègement de structure. Ce produit doit valider tous les tests classiques de l'automobile, notamment l'emboutissage, la mise en peinture, la tenue entre -40 ºC et 80 ºC, l'antigravillonage et la corrosion. Il est donc primordial d'avoir une adhésion suffisante pour permettre au composite de supporter les contraintes générées lors de la mise en oeuvre et les phénomènes de vieillissement en milieux hostiles. Dans notre cas, le polymère utilisé est un bicouche de 300 μm d'épaisseur. Il est constitué d'une couche adhésive de polypropylène greffé anhydride maléique et d'une couche de renfort de polypropylène. L'acier utilisé est un acier galvanisé DP 500 d'épaisseur 0.5 mm traitée chimiquement par une solution à base d'acide hexafluorotitanique. Afin d'optimiser les systèmes, on a étudié l'influence du traitement de surface (composition, nature, etc) sur l'adhésion avant et après vieillissement humide. L'objectif est de maitriser les paramètres prépondérants sur les niveaux d'adhérence, le mode de rupture et les mécanismes de délamination
The aim of this work is to develop a thick steel / polymer composite for weight savings in automotive industry. Formability, dent and corrosion resistance, damping behaviour, impact resistance (-30°C; + 80°C) could be offered by such materials. A key challenge when developing steel/polymer composite is to ensure a high steel/polymer adhesion level to face material processing (e.g. cutting, forming, ED-paint process) and ageing. The material described in this paper is a two-layer composite consisting of a rigid polymer layer of typically 0.3 mm and one thin Zn coated steel skin of 0.5mm. The metal is treated with a hexafluorotitanic acid based conversion coating (standard solution) and the polymer is a two-layer film displaying: - an adhesive layer (40 μm) of maleic anhydride grafted polypropylene - an reinforced polypropylene copolymer layer (260 μm) The influence of the conversion coating (nature, composition) and the ageing behavior in humid environment in order to optimize the steel/polymer multi-material have been studied in this work
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21

Liang, Honghe. "Synthesis and Characterization of A New Catechol Derived Coupling Agent." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1555671275779722.

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22

Beau, Bénédicte. "Relaxation nucléaire dans un polymère conducteur à comportement métallique, la polyaniline." Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10240.

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Ce memoire est consacre a l'etude des proprietes de transport electronique d'un polymere conducteur a comportement quasi-metallique, la polyaniline. La methode de dynamique de spin, basee sur des techniques de resonance magnetique nucleaire, constitue un moyen de s'affranchir d'une partie du desordre present dans les polymeres. Elle consiste a etudier le mouvement des porteurs de charge (polarons) par l'intermediaire des spins nucleaires fixes #1h disposes le long des chaines polymeres. La mesure de leur temps de relaxation spin-reseau, t#1, en fonction de la frequence, donne acces a la densite spectrale du mouvement des polarons et donc a la conduction microscopique. Dans une premiere partie, nous avons developpe cette methode sur le plan theorique afin de l'adapter a des situations particulieres que l'on peut rencontrer dans les polymeres conducteurs. Nous avons montre en particulier que lorsque le porteur de spin diffuse de facon 3d sur un reseau de n chaines 1d rassemblees dans un fagot infiniment long, la densite spectrale du mouvement est caracterisee par trois regimes : une diffusion 1d sur une chaine unique a haute frequence, suivie d'une diffusion 3d et, resultat nouveau, d'une diffusion pseudo-1d a tres basse frequence due au confinement du spin dans le fagot. Dans une seconde partie, nous avons mis en oeuvre la methode de dynamique de spin dans une large gamme de temperature (10 a 300k) et de frequence (10 a 500 mhz) sur des films de polyaniline metallique, dopee par l'acide camphre sulfonique (pani-csa). Nous avons interprete les resultats dans le cadre d'une image de desordre heterogene ou le polymere comporte des ilots cristallins metalliques 1d, connectes entre entre eux par des chaines electroniquement isolees 1d faiblement conductrices (regions amorphes). Nous avons montre que le vieillissement agit comme un processus de degradation progressive des ilots metalliques au profit des zones desordonnees. Enfin, nous avons analyse les resultats obtenus sur un echantillon de polyaniline partiellement dopee par l'acide chlorhydrique (pani-hcl) dans le cadre d'un modele decrivant la relaxation nucleaire spin-reseau dans les solides heterogenes. Cette etude a permis de confirmer le caractere heterogene du processus de protonation et de remonter a la taille des heterogeneites.
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23

Alencar, Ana Ellen Valentim de. "AvaliaÃÃo do uso de polÃmero EVA, resÃduo da indÃstria de calÃados (EVAR) e aditivos no desempenho reolÃgico de ligante asfÃltico de petrÃleo." Universidade Federal do CearÃ, 2009. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=5322.

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Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico
O desenvolvimento de novas metodologias no campo da engenharia rodoviÃria tem sido uma preocupaÃÃo, visando à melhoria da qualidade das vias pavimentadas, tornando-as mais seguras e resistentes. Algumas inovaÃÃes introduzidas nesta Ãrea tem sido praticadas com a aplicaÃÃo de ligantes asfÃlticos (LAs) modificados, que tem demonstrado melhorar o desempenho destes, contribuindo para a reduÃÃo da formaÃÃo das trilhas de roda e das trincas tÃrmicas. Neste estudo, o ligante asfÃltico (LA) brasileiro oriundo do Campo Fazenda Alegre foi modificado por copolÃmero de etileno e acetato de vinila (EVA) virgem, resÃduo da indÃstria de calÃados (EVAR) e fibra de coco (FC). Aditivos, como o lÃquido da castanha de caju (LCC) e o Ãleo extensor (OE) foram utilizados para melhorar a compatibilidade da mistura. O polÃmero e os aditivos foram caracterizados atravÃs de espectroscopia no infravermelho, termogravimetria e calorimetria exploratÃria diferencial. A avaliaÃÃo dos espectros FTIR dos ligantes apÃs envelhecimento simulado em estufa RTFOT, mostraram que os ligantes modificados com EVAR e EVA/FC foram mais resistentes ao processo oxidativo, provavelmente, devido à presenÃa de aditivos, como o carbonato de cÃlcio, na composiÃÃo do resÃduo. As curvas termogravimÃtricas dos LAs modificados apresentaram comportamento semelhante ao ligante puro. As propriedades reolÃgicas tambÃm foram avaliadas atravÃs de ensaios em: viscosÃmetro e reÃmetro de cisalhamento dinÃmico (DSR). O envelhecimento, de maneira geral, provoca aumento da rigidez e da viscosidade, porÃm as curvas mestras indicaram que o efeito do envelhecimento à mais expressivo nas temperaturas intermediÃrias a altas, e aumentaram a elasticidade ao longo do espectro de frequÃncias. A viscosidade zero shear (ZSV) obtida pelos modelos de Cross e Williamson apresentou-se mais elevada do que o modelo de Carreau. AlÃm disso, as imagens obtidas no microscÃpio de forÃa atÃmica (MFA) mostraram que o polÃmero EVA intumesceu devido à absorÃÃo de fraÃÃo aromÃtica do ligante, rompendo a estabilidade coloidal. Assim sendo, a adiÃÃo do Ãleo extensor preveniu a separaÃÃo de fases. Para o ligante modificado com EVAR, a mistura apresentou boa estabilidade à estocagem somente apÃs adiÃÃo de Ãleo extensor. A presenÃa do LCC e OE mostrou melhorar a susceptibilidade tÃrmica dos ligantes modificados.
The development of new methodologies in the field of road engineering has been a concern, aimed to the improvement of the quality of paved roads making them safer and more durable. Some innovations introduced in this area have been practiced with the application of modified asphalt binder (AB), demonstrated to improve asphalt binder performance, contributing to the reduction of the formation of wheel tracks and of thermal cracking. In this study, the Brazilian asphalt binder from Fazenda Alegre oil reserve was modified by virgin ethylene vinyl acetate copolymer (EVA), residue of the industry of footwears (EVAR) and coir fiber (CF). Additives, such as the cashew nut shell liquid (CNSL) and extensor oil (EO) were used to improve the compatibility of the mixture. The polymer and additives were characterized by means of infrared spectroscopy, termogravimetry and diferencial scanning calorimetry. The evaluation of the spectra FTIR of the binders after simulated aging in RTFOT, showed that the modified binders with EVAR and EVA/FC were more resistant to oxidative hardening, probably due to the presence of the additive, in the composition of the residue, such as the calcium carbonate. The termogravimetry curves of the modified ABs presented behavior similar to the pure binder. The rheological properties were also evaluated by tests with the viscometer and the dynamic shear rheometer (DSR). In general, ageing causes an increase in stiffness and viscosity, however the master curves indicated that the effect of aging is most significant in the intermediate to high temperatures and increases the elasticity along the spectrum of frequencies. The zero shear viscosity (ZSV) obtained by the models of Cross and Williamson was higher than the Carreau model. In addition atomic force microscopy (AFM) images were obtained in the showed that the EVA polymer sweeling suggest that part of the maltenic fraction of the binder was absorbed by the polymer. For the binder modified with EVAR, the mixture showed good stability only after the addition of the extensor oil. The presence of CNSL and EO improved the thermal susceptibility of the modified binders.
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24

Delannoy, Romain. "Études expérimentales et théoriques de la thermo-oxydation de réseaux époxy-amines." Thesis, Paris, HESAM, 2022. http://www.theses.fr/2022HESAE068.

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Utilisées couramment pour protéger des ouvrages en béton des contraintes environnementales extérieures, les matrices thermodurcissables époxy-amines subissent un vieillissement dégradant leurs propriétés d’usage. L’objectif principal de cette thèse est de comprendre les mécanismes à l’origine de la fragilisation. Pour comprendre la sélectivité intrinsèque de la structure moléculaire du réseau et identifier les sites sensibles au vieillissement thermo-oxydant, trois systèmes époxy-amines à base de DGEBA et de durcisseurs de la famille des éthylamines à la complexité croissante ont été choisis : DGEBA-EDA, DGEBA-DETA et DGEBA-TETA. Après vieillissement accéléré à différentes températures, les échantillons ont été caractérisés expérimentalement à différentes échelles. L’analyse par spectroscopie infrarouge a montré la formation majoritaire d’amides N−C=O et la disparition d’un signal attribué aux groupements N−CH2 portés par les segments « durcisseur » à toutes les températures et pour les trois réseaux. Une étude théorique complémentaire sur des molécules représentatives des motifs du réseau a permis de montrer que les liaisons C−H portées par ce site oxydable présente des enthalpies de dissociation (BDE) plus faibles que les autres sites et sont donc plus susceptibles de réagir pendant l’oxydation. On observe à l’échelle macromoléculaire, par des analyses calorimétriques et mécaniques multi-fréquentielles, un mécanisme prédominant de scissions de chaînes. Deux relaxations sous-vitreuses ont pu être identifiées pour DGEBA-DETA : l’une associée aux mouvements des hydroxypropyléthers −CH2−CH(OH)−CH2− dont l’intensité augmente au cours du vieillissement et l’autre, qui semble associé aux séquences « durcisseur », dont l’intensité diminue au cours du vieillissement. La corrélation entre oxydation de la structure moléculaire et évolution des propriétés mécaniques (élastiques et de rupture) des réseaux thermodurcissables a été établie
Epoxy-amine thermosets are often used in civil engineering to protect concrete structures, but they are themselves sensitive to chemical and physical ageing. This thesis is part of the ANR ECLIPS project aiming to characterize ageing and its effects on the mechanical and barrier properties of the materials. Three epoxy-amine networks made from DGEBA and ethylamine hardeners of increasing complexity – DGEBA-EDA, DGEBA-DETA, DGEBA-TETA – were chosen to accurately identify weak spots of the molecular structure. Different techniques were used to characterize multi-scale changes of the network after thermal ageing at different temperatures. At the molecular scale, the predominant formation of amide groups N−C=O was observed while an FTIR signal attributed to N−CH2 groups held by hardener segments was found to disappear with ageing. A complementary theoretical study on the Bond Dissociation Energies (BDE) was carried out using molecules representative of the repetitive pattern of the network. The C−H bond held by the same hardener N−CH2 group was found to be the most sensitive to oxidation as its BDE is the lowest. At the macromolecular scale, a predominant chain scission process was identified with ageing. Two sub-glass relaxations were observed for the DGEBA-DETA network. One associated to the hydroxypropyl ether group −CH2−CH(OH)−CH2− motions whose intensity increases with time. The other one of unknown origin quickly disappearing with ageing. Mechanical properties were characterized and a correlation with oxidation of the structure was established
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25

Scheffler, Christina. "Zur Beurteilung von AR-Glasfasern in alkalischer Umgebung." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-27035.

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AR-Glas wird in Form von Multifilamentgarn zur Verstärkung in textilbewehrtem Beton eingesetzt. Während des Herstellungsprozesses wird auf die AR-Glasfilamente die Schlichte aufgebracht, deren chemische Zusammensetzung maßgeblich die Qualität der Filament-Matrix-Grenzschicht bestimmt, sowie die chemische Beständigkeit im alkalischen Milieu gewährleistet. Zur Beurteilung der chemischen Beständigkeit in alkalischer Umgebung werden beschleunigte Alterungsversuche in wässrigen, alkalischen Lösungen durchgeführt. Die Reaktion von Hydroxid-Ionen mit dem Si-O-Si-Gruppen des Glasnetzwerkes führt zur Ausbildung hydratisierter Oberflächen und gelösten Silikaten. Das Ausmaß der Glaskorrosion ist von der chemischen Zusammensetzung der Glasfaser, der Schlichte bzw. Beschichtung und der alkalischen Lösung sowie von Zeit und Temperatur abhängig. Die beschleunigte Alterung von verschiedenen AR-Glasfasern in NaOH-Lösung sowie Zementlösung zeigt, dass sich der Korrosionsmechanismus aufgrund der vorhandenen Calcium-Ionen unterscheidet. Die Filamentbruchspannung wird anhand der Weibull-Verteilungsfunktion analysiert. Das mechanische Verhalten hängt deutlich von der chemischen Zusammensetzung der Alterungslösung ab, was zu unterschiedlichen Parametern der Weibull-Verteilungsfunktion sowie vermengten Verteilungen führen kann. Die Alterung in NaOH-Lösung führt zur Ausbildung einer korrodierten Schicht an der Filamentoberfläche. In Ca-haltigen Zementlösungen kommt es dagegen zu einer lokal begrenzten Korrosion. Für die Beurteilung verschiedener Polymerbeschichtungen werden Betonverbunde bei unterschiedlichen Temperaturen und Umgebungsfeuchten gelagert, wodurch geeignete Alterungsbedingungen evaluiert werden und den Vergleich der chemischen Beständigkeit unterschiedlicher Beschichtungen ermöglichen
Rovings made of AR-glass are used in textile reinforced concrete. During the manufacturing process the sizing is applied on the AR-glass filaments. The chemical constitution of the sizing determines the quality of the filament-matrix-interface but also the chemical durability of the glass filaments in alkaline environment. The durability is evaluated by accelerated ageing tests in aqueous, alkaline solutions. In alkaline solutions, the reaction of hydroxyl ions with Si-O-Si-groups of the glass network leads to the formation of hydrated surfaces and dissolved silicate. The rate of this corrosion depends on the chemical constitution of the fibre and the alkaline solution as well as on time and temperature. The investigation of the ageing of glass fibres with different chemical constitutions in NaOH and cement solutions shows that the corrosion mechanism changes due to the inhibiting effect of calcium ions. The strength distributions have been evaluated using a Weibull distribution function. The mechanical behaviour strongly depends on the chemistry of the solution and determines the parameters of the Weibull distribution function in terms of either single or mixed distributions. The corrosion in NaOH solution leads to a strong dissolution of the outer layer of the glass fibres, whereas during aging in cement solution at the same pH-value a limited, local attack was revealed. The evaluation of polymer coatings is realised by the ageing of concrete composites at different temperatures and humidities to deduce adequate ageing conditions for the comparison of different coatings
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26

Dubelley, Florence. "Mécanismes de dégradation des enveloppes barrières pour application panneaux isolants sous vide." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAI007/document.

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Le panneau isolant sous vide, PIV est principalement constitué d’un matériau de cœur nano-poreux encapsulé sous vide par une enveloppe barrière multicouche polymère-métal. Dans l’objectif d’étendre le domaine d’emploi des PIV sur le marché de l’isolation thermique du bâtiment, il est nécessaire d’améliorer les performances d’étanchéités et la résistance en température et humidité des complexes barrières métallisés, ces derniers représentant le point faible des PIV. Ce travail a pour objectif d’identifier les différentes modifications subies par ces complexes au cours de leurs fonctionnement et de déterminer les mécanismes à l’origine de leur dégradation prématurée. Des vieillissements à 70 °C et 90 %RH (conditions maximales d’utilisations identifiées pour le bâtiment français) ont été réalisés à la fois sur les composants, sur les complexes et sur les PIV pour des temps compris entre 1 et 870 jours. A l’échelle microscopique, la dégradation chimique du polyéthylène téréphtalate (PET) et de l’adhésif polyuréthane (PU) ont été étudiées par spectroscopie IR. Des marqueurs de l’hydrolyse ont ainsi pu être identifiés et ont permis de mettre en évidence la dégradation de ces deux composants au sein du complexe. L’hydrolyse ayant des répercussions directes sur les propriétés mécaniques des polymères explique la fragilisation à long terme de l’enveloppe. L’action de l’eau entraine également un gonflement et une plastification du PET, mis en évidence par mesure gravimétrique. Ces derniers peuvent entrainer des modifications de microstructure ayant des répercussions directes sur les mécanismes de transports des molécules d’eau et ainsi participer à la fragilisation du complexe. A l’échelle macroscopique, des mesures fines de retrait des films polymères ont été réalisées. Ces dernières ont été corrélées aux différentes délaminations de l’enveloppe barrière. Des analyses aux interfaces ont permis de déterminer le mode de rupture, adhésif ou cohésif
Vacuum Insulation Panels (VIPs) were already developed some time ago for low-temperature applications such as refrigerators. More recently, they have been used for the building application. They consist of a fine powder or fiber core material (fumed silica, glass fiber, PU foam) enveloped by a polymer-metal. The latter is responsible for preventing gas and water molecules from breaking the vacuum. Nevertheless, the use of VIPs for this application was limited for applications in severe conditions as for example: temperature, humidity and mechanical load. At high temperature and/or humidity, the most critical component of a VIP is the envelope: both for the tightness point of view and for its degradation. Consequently in these conditions, the vacuum was degraded and durability of the panel performance was decreased sharply.This work focuses on the degradation mechanisms of the polymer-metal envelope. The effect of hygrothermal ageing (70 °C and 90 %RH) on envelope was investigated at different scales: Microscopic: High humidity is at the origin of the hydrolysis of some components such as Polyethylene terephthalate (PET) and polyurethane adhesive (PU). Hydrolysis is directly at the origin of the changes mechanical properties, leading to embrittlement of the complex. An additional microstructural modifications was evidence in PET at high humidity and also contributes to embrittlement of the complex. Macroscopic: shrinkage of polymer film seems to be the origin of debonding in polymer-metal multilayer
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27

Dostál, Filip. "Vliv druhu a dávky polymeru na vlastnosti modifikovaných pojiv." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2020. http://www.nusl.cz/ntk/nusl-409806.

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The diploma thesis is focused on polymer modified binders with different polymer doses. The theoretical part describes the history of the use of bitumen, the extraction of bitumen from oil and behavious of the polymer type SBS/SB, which is used in the diploma thesis on modified binders. Further, the theoretical part describes the empirical and functional tests of bitumen binders. In the practical part the results of indidual tests are presented and compared with the standard ČSN 65 7222-1. At the end of the diploma thesis are summarized results of work and evaluation of binders with the best achieved properties.
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28

Rannou, Patrice. "Poly(aniline) : synthèse, mise en oeuvre et vieillissement." Université Joseph Fourier (Grenoble ; 1971-2015), 1998. http://www.theses.fr/1998GRE10080.

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Ce travail est consacré à la synthèse, la mise en œuvre et le vieillissement d'un polymère conducteur (pc) : la polyaniline (pani). Deux morphologies ont été étudiées : des poudres divisées de pani dopee par l'acide chlorhydrique (pani-hci) et des films de pani dopee par l'acide camphre sulfonique (csa) obtenus par l'évaporation de solutions dans le m-cresol. Dans une première partie, nous présentons la synthèse chimique basse température par voie oxydante de la pani. Le contrôle des paramètres de synthèse a permis de préciser le mécanisme de polymérisation et d'obtenir des polymères de masse moléculaire élevée ou les défauts chimiques du squelette macromoléculaire sont minimises. La deuxième partie présente une revue de connaissances relatives au dopage, à la structure chimique et cristallographique et à l'aptitude à la mise en œuvre de ce pc. Les caractérisations des différentes pani synthétisées ont permis d'étudier les relations structure/propriétés en soulignant les bénéfices apportés par l'amélioration du protocole de synthèse. La définition d'une stratégie de choix des associations pani/dopant/solvant a permis l'obtention de films de pani qui présentent un comportement métallique. La troisième partie de ce recueil est consacrée au vieillissement de poudres divisées de pani-hci et de films de pani-csa. Cette thématique est abordée selon deux aspects : l'identification et l'étude des mécanismes réactionnels qui conduisent à la détérioration de la conductivité ainsi que la prévision du comportement à long terme de la conductivité par la mise en place de tests de vieillissement accélèré.
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29

Scheffler, Christina. "Zur Beurteilung von AR-Glasfasern in alkalischer Umgebung: Evaluation of AR-glas fibres in alkaline environment." Doctoral thesis, Leibniz-Institut für Polymerforschung Dresden e.V, 2009. https://tud.qucosa.de/id/qucosa%3A25230.

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AR-Glas wird in Form von Multifilamentgarn zur Verstärkung in textilbewehrtem Beton eingesetzt. Während des Herstellungsprozesses wird auf die AR-Glasfilamente die Schlichte aufgebracht, deren chemische Zusammensetzung maßgeblich die Qualität der Filament-Matrix-Grenzschicht bestimmt, sowie die chemische Beständigkeit im alkalischen Milieu gewährleistet. Zur Beurteilung der chemischen Beständigkeit in alkalischer Umgebung werden beschleunigte Alterungsversuche in wässrigen, alkalischen Lösungen durchgeführt. Die Reaktion von Hydroxid-Ionen mit dem Si-O-Si-Gruppen des Glasnetzwerkes führt zur Ausbildung hydratisierter Oberflächen und gelösten Silikaten. Das Ausmaß der Glaskorrosion ist von der chemischen Zusammensetzung der Glasfaser, der Schlichte bzw. Beschichtung und der alkalischen Lösung sowie von Zeit und Temperatur abhängig. Die beschleunigte Alterung von verschiedenen AR-Glasfasern in NaOH-Lösung sowie Zementlösung zeigt, dass sich der Korrosionsmechanismus aufgrund der vorhandenen Calcium-Ionen unterscheidet. Die Filamentbruchspannung wird anhand der Weibull-Verteilungsfunktion analysiert. Das mechanische Verhalten hängt deutlich von der chemischen Zusammensetzung der Alterungslösung ab, was zu unterschiedlichen Parametern der Weibull-Verteilungsfunktion sowie vermengten Verteilungen führen kann. Die Alterung in NaOH-Lösung führt zur Ausbildung einer korrodierten Schicht an der Filamentoberfläche. In Ca-haltigen Zementlösungen kommt es dagegen zu einer lokal begrenzten Korrosion. Für die Beurteilung verschiedener Polymerbeschichtungen werden Betonverbunde bei unterschiedlichen Temperaturen und Umgebungsfeuchten gelagert, wodurch geeignete Alterungsbedingungen evaluiert werden und den Vergleich der chemischen Beständigkeit unterschiedlicher Beschichtungen ermöglichen.
Rovings made of AR-glass are used in textile reinforced concrete. During the manufacturing process the sizing is applied on the AR-glass filaments. The chemical constitution of the sizing determines the quality of the filament-matrix-interface but also the chemical durability of the glass filaments in alkaline environment. The durability is evaluated by accelerated ageing tests in aqueous, alkaline solutions. In alkaline solutions, the reaction of hydroxyl ions with Si-O-Si-groups of the glass network leads to the formation of hydrated surfaces and dissolved silicate. The rate of this corrosion depends on the chemical constitution of the fibre and the alkaline solution as well as on time and temperature. The investigation of the ageing of glass fibres with different chemical constitutions in NaOH and cement solutions shows that the corrosion mechanism changes due to the inhibiting effect of calcium ions. The strength distributions have been evaluated using a Weibull distribution function. The mechanical behaviour strongly depends on the chemistry of the solution and determines the parameters of the Weibull distribution function in terms of either single or mixed distributions. The corrosion in NaOH solution leads to a strong dissolution of the outer layer of the glass fibres, whereas during aging in cement solution at the same pH-value a limited, local attack was revealed. The evaluation of polymer coatings is realised by the ageing of concrete composites at different temperatures and humidities to deduce adequate ageing conditions for the comparison of different coatings.
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30

Planche, Marie-France. "Etude des mécanismes de vieillissement du polymère conducteur polypyrrole et améliorations possibles." Université Joseph Fourier (Grenoble), 1994. http://www.theses.fr/1994GRE10239.

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Le polypyrrole, synthetise par voie chimique, est d'une elaboration facile et presente de nombreuses applications potentielles. Dans ce travail, sa synthese a ete optimisee de facon a obtenir un polymere de conductivite elevee et de bonne stabilite. En outre, cette etude a permis une meilleure comprehension des mecanismes reactionnels de la synthese chimique. Cependant, le principal probleme pour la plupart des applications reste la degradation ambiante de ce materiau. La modelisation obtenue de la perte de conductivite dans le temps, en temperature, est caracteristique d'un mecanisme de conduction par sauts ; la degradation du polypyrrole a alors ete attribuee a une augmentation de la taille de la couche isolante separant les domaines conducteurs. De plus, la rpe a montre que la concentration en polarons etait constante au cours du vieillissement mais que leur mobilite diminuait. Par ailleurs, l'analyse electrochimique a mis en evidence une diminution de la mobilite des anions dopants au cours de la degradation
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31

Dal, Maso Fabrice. "Influence du vieillissement thermique sur la morphologie et les proprietes du poly(fluorure de vinylidene) (pvf#2)." Paris 6, 1992. http://www.theses.fr/1992PA066104.

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L'objet de la these est de decrire et de correler les evolutions de la morphologie et des proprietes du poly(fluorure de vinylidene) (pvf#2) au cours du vieillissement thermique, en fonction des conditions de mise en forme, de la temperature et de la duree de recuit. Contrairement a la plupart des etudes sur le pvf#2, les echantillons utilises sont obtenus par compression sous forme de plaques epaisses de plusieurs millimetres. Le mode de refroidissement est le parametre de moulage qui influence le plus le comportement a long terme du materiau. Du point de vue mecanique, le materiau conserve de bonnes proprietes et se stabilise apres quelques jours de recuit. Un aspect etonnant de ce materiau est que sa ductilite augmente, bien que sa cristallinite augmente egalement. La micro-structure du materiau est un arrangement complexe d'unites cristallines et amorphes, qui peuvent etre considerees a plusieurs echelles. La description de la micro-structure a donc necessite l'emploi de plusieurs techniques de caracterisation physico-chimiques (calorimetrie, diffraction des rayons x, microscopie, etc. ). La structure cristalline preferentiellement adoptee est la phase alpha. Le vieillissement n'entraine pas de transitions allotropiques. Par contre, l'organisation des zones cristallines est complexe et on observe des evolutions au niveau de la conformation des chaines, des empilements des chaines dans le cristal et de l'organisation des micro-domaines cristallins. C'est grace a la simulation des spectres des rayons x aux grands angles qu'il a ete possible de comprendre les evolutions des zones cristallines au cours du recuit. Une seconde approche, originale, a consiste a coupler un module de simulation de spherolites avec une simulation de diffraction des rayons x aux petits angles. Ces deux methodes de simulation informatique nous ont permis d'ameliorer la description de la structure du pvf#2 et d'autres polymeres semi-cristallins
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32

Ali, Mahdi. "Study of the bitumen aging effects on the rheological properties and fatigue behavior." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16255/.

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A study of bitumen aging effects on the rheological properties and fatigue behavior is carried out on five polymer modified bitumen provided by an oil company. Dynamic Shear Rheometer (DSR), is used to perform advanced experimental investigation. It allows practicing frequency sweep tests, fatigue tests and time sweep tests. Polymer modified bitumen with different percentage of SBS with or without the presence of crumb rubber are tested before and after short and long aging processes. Master curves were generated based on frequency sweep tests data, they are studied, and a comparison was conducted between each bitumen before and after aging. In this thesis, the DSR is presented, as well as the testing procedure and the tested materials. A fatigue life analysis of the results, based on the use of two different criteria, the first criterion is classically used: it consists in defining the failure as a 50% loss of the initial stiffness. The other criteria based on dissipated energy data. This thesis provides results which show the effects of several factors on fatigue and healing response such as bitumen type, ageing, the presence of rubber and polymer modification.
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33

Felipe, Raimundo Nonato Barbosa. "Efeitos da radia??o uv, temperatura e vapor aquecido nos comp?sitos polim?ricos: monitoramento, instabilidade estrutural e fratura." Universidade Federal do Rio Grande do Norte, 2012. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15594.

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Made available in DSpace on 2014-12-17T14:57:54Z (GMT). No. of bitstreams: 1 RaimundoNBF_TESE_1-104.pdf: 5288172 bytes, checksum: 0543c551bb4ef0aded2a4c286f66043d (MD5) Previous issue date: 2012-09-28
The application of composite materials and in particular the fiber-reinforced plastics (FRP) has gradually conquered space from the so called conventional materials. However, challenges have arisen when their application occurs in equipment and mechanical structures which will be exposed to harsh environmental conditions, especially when there is the influence of environmental degradation due to temperature, UV radiation and moisture in the mechanical performance of these structures, causing irreversible structural damage such as loss of dimensional stability, interfacial degradation, loss of mass, loss of structural properties and changes in the damage mechanism. In this context, the objective of this thesis is the development of a process for monitoring and modeling structural degradation, and the study of the physical and mechanical properties in FRP when in the presence of adverse environmental conditions (ageing). The mechanism of ageing is characterized by controlled environmental conditions of heated steam and ultraviolet radiation. For the research, it was necessary to develop three polymer composites. The first was a lamina of polyester resin reinforced with a short glass-E fiber mat (representing the layer exposed to ageing), and the other two were laminates, both of seven layers of reinforcement, one being made up only of short fibers of glass-E, and the other a hybrid type reinforced with fibers of glass-E/ fibers of curaua. It should be noted that the two laminates have the lamina of short glass-E fibers as a layer of the ageing process incidence. The specimens were removed from the composites mentioned and submitted to environmental ageing accelerated by an ageing chamber. To study the monitoring and modeling of degradation, the ageing cycles to which the lamina was exposed were: alternating cycles of UV radiation and heated steam, a cycle only of UV radiation and a cycle only of heated steam, for a period defined by norm. The laminates have already undergone only the alternating cycle of UV and heated steam. At the end of the exposure period the specimens were subjected to a structural stability assessment by means of the developed measurement of thickness variation technique (MTVT) and the measurement of mass variation technique (MMVT). Then they were subjected to the mechanical tests of uniaxial tension for the lamina and all the laminates, besides the bending test on three points for the laminates. This study was followed by characterization of the fracture and the surface degradation. Finally, a model was developed for the composites called Ageing Zone Diagram (AZD) for monitoring and predicting the tensile strength after the ageing processes. From the results it was observed that the process of degradation occurs Abstract Raimundo Nonato Barbosa Felipe xiv differently for each composite studied, although all were affected in certain way and that the most aggressive ageing process was that of UV radiation, and that the hybrid laminated fibers of glass-E/curaua composite was most affected in its mechanical properties
A aplica??o dos materiais comp?sitos e em particular os pl?sticos refor?ados por fibras (PRF) tem conquistado espa?o, gradativamente, dos materiais ditos convencionais, por?m desafios t?m sido colocados quando sua aplica??o ocorre em equipamentos e estruturas mec?nicas que ficar?o expostos a condi??es ambientais adversas, principalmente quando se tem a influ?ncia da degrada??o ambiental do tipo temperatura, radia??o UV e umidade, no desempenho mec?nico dessas estruturas, ocasionando danos estruturais irrevers?veis tais como: perda de estabilidade dimensional, degrada??o interfacial, perda de massa, perda das propriedades estruturais e altera??es no mecanismo de dano. Neste contexto a presente tese tem como objetivo o desenvolvimento de um processo de monitoramento e modelagem da degrada??o estrutural, e o estudo das propriedades f?sicas e mec?nicas, em PRF quando em presen?a de condi??es ambientais adversas (envelhecimento). O mecanismo de envelhecimento ? caracterizado por condi??es ambientais controladas de vapor aquecido e de radia??o ultravioleta. Para a pesquisa foi desenvolvido tr?s comp?sitos polim?ricos, o primeiro uma l?mina de resina poli?ster refor?ado com manta de fibras curtas de vidro-E (representando a camada exposta ao envelhecimento) e dois laminados, ambos de sete camadas de refor?o, sendo um constitu?do s? com manta de fibras curtas de vidro-E, e o outro do tipo h?brido refor?ado com fibras de vidro-E/fibras de curau?. Ressalta-se que os dois laminados t?m a l?mina de fibras curtas de vidro-E como camada de incid?ncia do processo de envelhecimento. Os corpos de provas (CP s) foram retirados dos comp?sitos citados e submetidos ao envelhecimento ambiental acelerado atrav?s da c?mara de envelhecimento. Para o estudo do monitoramento e modelagem da degrada??o, os ciclos de envelhecimento a que foram expostos ? l?mina foram: ciclos alternados de radia??o UV e vapor aquecido, ciclo somente de radia??o UV e o ciclo somente de vapor aquecido, por um per?odo definido em norma. J? os laminados foram submetidos a apenas ao ciclo alternado de UV e vapor aquecido. Ao t?rmino do per?odo de exposi??o os CP s foram submetidos ? avalia??o da estabilidade estrutural mediante a t?cnica desenvolvida de medi??o de varia??o de espessura (TMVE) e a t?cnica de media??o de varia??o de massa (TMVM). Em seguida os mesmos foram submetidos aos ensaios mec?nicos de tra??o uniaxial para a l?mina e todos os laminados, al?m do ensaio de flex?o em tr?s pontos para os laminados. Esse estudo foi seguido da caracteriza??o da fratura e da degrada??o superficial. Por fim, foi desenvolvido um modelo para os Resumo Raimundo Nonato Barbosa Felipe xii comp?sitos denominado de Diagrama da Zona de Envelhecimento (DZE) para o monitoramento e predi??o da resist?ncia mec?nica ? tra??o ap?s os processos de envelhecimento. Ao t?rmino das an?lises foi observado que o processo de degrada??o se d? de forma diferente para cada comp?sito pesquisado, no entanto todos foram afetados, o processo de envelhecimento mais agressivo foi o de radia??o UV, e que o comp?sito que foi mais afetado em suas propriedades mec?nicas foi o laminado h?brido de fibras de vidro-E/curau?
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34

Zábranský, Ivo. "Vlastnosti nízkoteplotních polymerem modifikovaných asfaltů." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2019. http://www.nusl.cz/ntk/nusl-392123.

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The Diploma thesis is focus on polymer modified bitumen for warm mix asphalt. The theoretical part of the thesis describes additives which influence the properties of bitumen for their use and reduction of production and service temperatures. Further, the theoretical part describes the conclusions from the researches. This part also describes empirical and functional tests of bituminous binders. The practical part presents the results of individual tests. Tests were performed on samples of non-aged, aged by RTFOT and RTFOT + PAV methods. The results of the work and the assessment of the suitability of bituminous binders are summarized at the end of the thesis.
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35

Dao, Ngoc Long. "Impulse ageing of polymeric materials." Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/201099/.

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Impulse over-voltage is a common phenomenon in electric power systems. A switching impulse is created by a switching surge or local fault while a lightning impulse is due to direct lightning strike to high voltage plant such as an overhead line. Both impulse events create travelling waves in the system, damaging insulation components and equipment. This work is concerned with the hypothesis that lightning impulses can lead to accelerated ageing of extruded polymeric cables. The results show that there may well be a reduction in electric field strength of the insulation of a power cable that experiences a lot of impressed lightning impulse over-voltages. Pre-designed shaped polyethylene material sample discs have been manufactured using a mould tool. The samples then have been electrically aged using an impulse generator. A real-time software based monitoring tool has been designed to control the impulse wave-shape and process the measurement data. Sets of identical lightning impulses were applied to samples and this was then followed by ramped AC breakdown tests. The obtained results were analyzed using the Weibull distribution to identify any differences in lifetime between aged and un-aged samples. This thesis also provides insight into the dominant ageing processes through the analysis of dielectric spectroscopy and space charge measurement data. In order to quantify the effects of dielectric ageing due to impressed lighting impulse over voltages, experiments have also been undertaken using samples that have been aged under UV light and thermally. Analysis of obtained results reveals that mechanisms of these two ageing processes are significantly different from the mechanisms due to lightning impulse ageing
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36

Kriesten, Ute. "Quantitative aspects of physical ageing in polymers." Thesis, University of Aberdeen, 1993. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU055702.

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Physical ageing, which is the spontaneous increase of mechanical relaxation times after quenching from above the glass transition temperature, was the subject of this study. The quench at the beginning of physical ageing serves to 'rejuvenate' the material. This means it reproducibly creates a frozen-in non-equilibrium material structure with an increased mobility which then relaxes towards equilibrium. The creep behaviour is used to represent the molecular mobility, and was measured with small strain torsional creep tests. As the mobility decreases the retardation time increases. A quantitative evaluation of the changes in the creep behaviour as a result of physical ageing was undertaken. The creep data were combined with measurements that tested other thermodynamic quantities also known to exhibit recovery. These are the specific enthalpy measured with DSC (diferential scanning calorimetry) and specific volume measured using a density gradient column. Physical ageing experiments on polystyrene (an amorphous polymer) were intended to choose between the wide variety of existing theories. No appreciable change in the relaxation spectrum was found; howver, a closer look at the common superposition procedures revealed that such change might easily remain undetected. The experiments measuring volume relaxation and enthalpy relaxation show that physical ageing cannot be related in a straightforward sense to enthalpy relaxation or volume relaxation. In polypropylene, a semicrystalline polymer, various recovery effects were observed at room temperature. This is above the material's glass transition temperature and can therefore not be explained in the same terms as physical ageing in polystyrene. The phenomena are however strikingly similar. Not only does the relaxation spectrum of polypropylene shift to longer relaxation times without much change in the spectrum, but also volume relaxation and enthalpy relaxation are observed in magnitudes comparable to polystyrene. The enthalpy relaxation as observed using DSC shows complexities which help to understand the mechanism of structural relaxation in polypropylene.
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37

Lai, Chee-Hoong. "Physical ageing and dimensional changes of acrylate polymers /." Title page, table of contents and summary only, 1992. http://web4.library.adelaide.edu.au/theses/09PH/09phl185.pdf.

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38

Guetta, Brigitte. "Vieillissement hygrothermique de composites a matrice psp : etude cinetique, mecanique et spectroscopique." Paris, ENMP, 1987. http://www.theses.fr/1987ENMP0057.

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Papet, Gérard. "Etude cinetique du vieillissement radiochimique du polyethylene." Paris, ENSAM, 1987. http://www.theses.fr/1987ENAM0009.

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Etude de la radiolyse gamma du polyethylene basse densite dans l'air et a temperature ambiante. Les profils de distribution dans l'epaisseur de la concentration en carbonyles presentent une decroissance a une profondeur d'environ 180 microns. Determination des parametres cinetiques dans le cas ou la diffusion ne controle pas le vieillessement. Etude de modeles theoriques et de l'evolution des proprietes mecaniques pendant la degradation radiochimique
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40

Pubellier, Pierre. "Influence de charges micrométriques sur le vieillissement de composites à matrice polymère." Thesis, Paris Est, 2017. http://www.theses.fr/2017PESC1177/document.

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La compréhension des phénomènes de vieillissement dans les élastomères réticulés chargés par des particules inorganiques est primordiale pour proposer un critère de fin de vie aux câbles électriques en usage au sein des centrales nucléaires. En effet, la gaine isolante de ces câbles met en jeu une matrice élastomère formulée par différents adjuvants et charges. Une quantité importante de particules inorganiques, du tri-hydrate d’aluminium (ATH), est usuellement introduite au sein de la matrice afin de lui conférer des propriétés anti-feu satisfaisantes. Les particules utilisées sont de taille micrométrique et du fait de la faible surface de contact polymère / charge intrinsèque aux microcomposites, l’ajout d’ATH est supposé n’impliquer aucune modification des mécanismes de vieillissement de la matrice. Or, des travaux récents ont mis en évidence un comportement au vieillissement thermique différent entre une matrice d’EPDM (élastomère à base d’unités éthylène, propylène et diène) chargée par des particules d’ATH micrométriques et la même matrice, sans ATH.L’objectif de cette thèse est de renseigner plus en détail l’effet du vieillissement thermo- et radio-oxydatif sur une matrice d’EPDM chargée par des particules d’ATH et de mieux comprendre les modifications observées. L’influence de paramètres physico-chimiques importants (taux de charges, fonctionnalisation de la surface des charges) sur le comportement en vieillissement sera en particulier abordée. Nous nous sommes, plus précisément, attachés à décrire l’évolution du réseau à l’échelle macromoléculaire, en déterminant les différentes populations du réseau (chaînes élastiquement actives, chaînes pendantes et extractibles) ainsi que la distribution de la densité de réticulation. Ces données ont été obtenues par le biais de la RMN (Résonance Magnétique Nucléaire) du solide.Les résultats de ces expériences montrent une diminution importante de la période d’induction au vieillissement thermo-oxydatif des matrices d’EPDM lors de l’ajout de particules d’ATH dans le réseau. Cet effet dépend fortement de la quantité de charges ATH introduites et de la fonctionnalisation ou non de leur surface. Lors du vieillissement radio-oxydatif, en revanche, aucune modification des cinétiques de vieillissement n’est observée. La confrontation des données issues des deux types de vieillissement suggère une modification des mécanismes d’amorçage de l’oxydation, dans les réseaux d’EPDM, lorsque ces derniers sont chargés par des particules d’ATH. Le rôle des interfaces charge / matrice semble donc déterminant dans ces modifications
A deep understanding of the ageing behaviour within cross-linked elastomers filled by inorganic particles is a key feature to propose a criterion for the end of life of electric cables in nuclear power plants. Indeed, materials used for wire insulation are usually composed of rubbers designed with several adjuvants and fillers. A significant amount of inorganic particles, such as aluminium trihydrate (ATH), is usually incorporated with the polymer matrix in order to achieve satisfactory fire-retardant properties. The ATH particles used are characterized by a micrometric-size and due to the weak polymer / filler contact area involved in such composites, the ageing mechanisms of the polymer matrix are expected to be essentially unchanged compared to the ones involved in the unfilled matrix. However, recent studies pointed out some differences in the thermal-ageing mechanisms between a cross-linked EPDM rubber (elastomer based on ethylene, propylene and diene units) filled by micrometric ATH (aluminium trihydrate) particles and the corresponding unfilled cross-linked EPDM.In that respect, this work aims at investigating the extent of generality of the above-mentioned filler effect on both thermo- and radio-oxidative ageing behaviour of an EPDM matrix filled by ATH particles. In particular, the influence of both filler content and filler surface functionalization is investigated. A special attention was paid to the evolution of the network at the macromolecular scale by determining the fraction of the various network components (elastically active chains, dangling chains and extractibles) as well as the cross-link density distribution. Such information have been derived using solid-state NMR (Nuclear Magnetic Resonance).The results obtained evidence a significant decrease of the thermal-ageing induction period for the EPDM network filled by ATH particles. This effect display a strong dependence with the amount and the surface functionalization of the ATH particles. However, no modifications of the oxidation kinetics may be observed under radio-chemical ageing. The comparison between the results suggests a possible modification of the oxidation initiation mechanisms within EPDM networks filled by ATH particles. Therefore, interfacial areas should play a great role in the observed modifications
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41

Msuya, Winston Filipo Seth. "The influence of physical ageing and morphology on yield in polypropylene." Thesis, [Hong Kong] : University of Hong Kong, 1988. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12434036.

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42

Hotař, Petr. "Reologické vlastnosti asfaltových pojiv." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226951.

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The comparison of rheological properties (complex shear modulus and phase angle and dynamic viscosity) of four paving bitumens and two polymer modified bitumens is performed in this diploma thesis. Furthermore, the empirical tests (needle penetration and softening point) were determined on these binders. Effect of asphalt binders aging was modeled using RTFOT test and modified RTFOT test (3 x RTFOT).
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43

Nawaz, Sohail. "Preparation and long-term performance of poly(ethylene-co-butyl acrylate) nanocomposites and polyethylene." Doctoral thesis, KTH, Polymera material, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-104685.

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The current study discusses the preparation and long-term performance of polymer composites used for various purposes under different ageing conditions. The first part deals with the preparation and characterization of polymer nanocomposites based on poly(ethylene-co-butyl acrylate) (EBA–13 and EBA–28 with 13 and 28 wt % butyl acrylate, respectively) and 2–12 wt % (0.5–3 vol %) of aluminum oxide nanoparticles (two types with different specific surface areas and different hydroxyl-group concentrations; uncoated and coated with, respectively, octyltriethoxysilane and aminopropyltriethoxysilane). The nanocomposite with EBA–13 showed better overall nanoparticle dispersion while EBA–28 resulted in poor dispersion, probably due to insufficiently high shear forces acting during extrusion mixing which were unable to break down nanoparticle agglomerates. The activity of hindered phenolic antioxidant (0.2 wt%) in all EBA nanocomposites was assessed by determining the oxidation induction time using DSC. The composites containing uncoated aluminium oxide nanoparticles showed a much shorter initial OIT than the pristine polymer with the same initial concentration of antioxidant, indicating adsorption of antioxidant onto the nanoparticle surfaces. Composites containing coated nanoparticles showed a significantly smaller decrease in the initial OIT, suggesting the replacement of hydroxyl groups with organic silane tails, decreasing the concentration of available adsorption sites on the nanoparticle surfaces. The decrease in OIT with increasing ageing time in dry air at 90 °C of the nanocomposites was slower than that of the unfilled pristine polymer, suggesting a slow release of antioxidant from adsorption sites. The EBA nanocomposites exposed to liquid water at 90°C showed faster decrease of OIT than samples exposed to dry or humid air. The migration rate of antioxidant was controlled by the boundary conditions in the case of ageing in humid air and liquid water. The antioxidant diffusivity was lower for the composites containing uncoated ND than for the composites containing ND coated with octyltriethoxysilane or aminopropyltriethoxysilane. The migration and chemical consumption of deltamethrin DM, (synthetic pyrethroid) and synergist piperonyl butoxide from molded polyethylene sheets was also studied. Deltamethrin and piperonyl butoxide are often used for food  storage and insect control purposes. DM showed no signs of crystallization and remained in a liquid state after being cooled to room temperature. Exposure of polyethylene compound sheets to liquid water (at 80 & 95 °C), caused degradation and hydrolysis of the ester bond in the DM, present in the prepared material, and generated species containing hydroxyl groups. Liquid chromatography and infrared spectroscopy showed a significant migration of the active species in liquid water, whereas in air at 80 °C (60 and 80 %RH) the loss of DM and PBO was negligible over 30 days. The long-term performance of medium-density polyethylene stabilized with six different phenolic antioxidants (0.1 wt%) in aqueous chlorinated media at 70 °C was studied. The results were compared with data for previously studied solutions of antioxidants in squalane (a liquid, low molar mass analogue of polyethylene). A linear relationship was established between the time to reach antioxidant depletion in polyethylene tape samples and the time in squalane samples. Infrared spectroscopy and scanning electron microscopy of drawn samples revealed the onset of surface oxidation and surface embrittlement in tape samples exposed beyond the time for antioxidant depletion.

QC 20121109


Cable insulation materials
Loss of deltamethrin and pipronyl butoxide from polyethylene
long-term performance of polyethylene in chlorine dioxide water
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44

Swanson, Nicole. "Polybutadiene Graft Copolymers as Coupling Agents in Rubber Compounding." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1473158881.

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45

Bruce, Graham Philip. "Ageing of Outdoor Polymeric Insulation under HVDC." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.505489.

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46

Mubarak, Yousef Ahmad. "A study of the crystallisation and ageing of isotactic polypropylene." Thesis, Queen's University Belfast, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326290.

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47

Avena-Barthelemy, Anne. "Comportement a long terme de materiaux composites immerges a grande profondeur." Paris, ENMP, 1987. http://www.theses.fr/1987ENMP0049.

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Etude du vieillissement de polymeres renforces ou non de fibres de verre ou de mousses syntactiques immerges dans l'eau sous des pressions de 0 a 300 bars. Adsorption d'eau, proprietes mecaniques, eclatement des microspheres dans les mesures syntactiques
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48

Pedoto, Giuseppe. "Characterization and Modelling of the Thermomechanical and Ageing Behavior of PEKK and C/PEKK Composites for Aircraft Applications at High Temperatures (above the Glass Transition Temperature) Characterization of the mechanical behavior of PEKK polymer and C/PEKK composite materials for aeronautical applications below and above the glass transition temperature." Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2020. http://www.theses.fr/2020ESMA0011.

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La sensibilisation accrue aux questions environnementales concerne aujourd'hui les structures aéronautiques en termes d'impact environnemental et traitements de fin de vie. Dans cette optique,la possibilité de remplacer, dans les composites à matrice organique (CMO) utilisés pour des applications aéronautiques, leur matrice thermodurcissable non recyclable par une matrice thermoplastique recyclable est étudiée. En outre, les polymères thermoplastiques, tels que le PEKK, ont la possibilité d'être utilisés dans des structures plus chaudes (par exemple le pylône d'un avion), faisant l'objet de sollicitations de longue durée (fluage). Les températures de service de ces structures plus élevées que celles de la température de transition vitreuse du PEKK : il en découle, dans le matériau, une perte de propriétés due au changement d'état de solide à caoutchoutique, et éventuellement l'activation de phénomènes de cristallisation etde dégradation, qui pourraient également interagir. Ce travail vise à identifier et à modéliser ces mécanismes caractérisant le comportement du PEKK, dans ces conditions extrêmes particulières.Ceci est réalisé à partir de l'analyse des résultats des essais thermomécaniques, physico-chimiques et thermomécaniques couplés avec l’oxydation. Le modèle analytique 1-D du comportement duPEKK qui résulte de l’analyse des essais est étendu en 3-D et implémenté dans une méthode d'homogénéisation/localisation semi-analytique multi-échelle pour simuler le comportement dans mêmes conditions de composites stratifiés à matrice PEKK, en faisant varier l'orientation des plis et la séquence d'empilement
The nowadays increased awareness towards environmental issues concerns aircraft structures in terms of environmental impact and end-of-life disposal. In this optics, the possibility of replacing in the organic matrix composites (CMO) employed for aircraft applications the non-recyclable thermosetting matrix with a recyclable thermoplastic one is investigated. Moreover, thermoplastic polymers, such PEKK, have the possibility of being employed in warmer structures (e.g. the aircraft pylon), undergoing long duration solicitations (creep).The service temperatures for those structures are higher than the PEKK glass transition temperature, provoking, in the material, a loss of properties deriving from a change of state from solid to rubber, and possibly the activation of crystallization and degradation phenomena, which could also interact. This work aims to identify and model the mechanisms characterizing PEKK behavior, under the structure operative service conditions. This is achieved from the analysis of the results of thermomechanical, physical-chemical and coupled thermomechanical/oxidation tests. The resulting 1-D analytical model of the PEKK behavior, is extended in 3-D and implemented in a multi-scale semi-analytical homogenization / localization method to simulate PEKK based composites under the same conditions, varying the plies orientation and stacking sequence
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Humphreys, Adrian MacMahon. "Characterisation of smoke and smoke ageing mechanisms from thermally decomposing polymers." Thesis, London South Bank University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390297.

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50

Sebillotte, Eric. "Dégradation sous champ électrique alternatif du polypropylène imprégné : influence des époxydes." Grenoble INPG, 1989. http://www.theses.fr/1989INPG0032.

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Vieillissement de condensateurs moyenne tension dit "tout film" au polypropene impregne: influence d'epoxydes comme additif au liquide d'impregnation (ralentissement des mecanismes conduisant au vieillissement du film, inities dans une couche de liquide de quelques mu d'epaisseur entre le film et l'electrode). Etude sur des modeles de condensateurs a geometrie plane. Mesure de la rigidite dielectrique du film impregne
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