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1
Kulkarni, Aishwarya, and Harshini Dasari. "Current Status of Methods Used In Degradation of Polymers: A Review." MATEC Web of Conferences 144 (2018): 02023. http://dx.doi.org/10.1051/matecconf/201814402023.
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Degradation of different polymers now a day is the most crucial thing to carry out. It possesses threats to human health as well as to the environment. Different polymers like PVA, PVC, and PP with high density and low density are one of the most consumed by population and also their degradation is a bit difficult. For this many people have started working on effective methods of degradation of these polymers. This can be done by thermal degradation and pyrolysis which requires high temperature, bio degradation using starch, bacteria etc and photo degradation. Traditional gravimetric and respirometric techniques are the methods currently used in testing. They fit readily for degradable polymeric materials usually. Also they are well suited for biodegradable components with polymer blends. But the recent polymer generation is comparatively resistant to bio degradation of polymers hence they cannot be used here. The polymer matrices are readily present in the plasticizers boosting the strength of polymeric material hence in addition; there is the mechanism of degradation. The information on various methods discussed in this review is planned to illustrate a best fit of methods for those who are interested in testing the degradation of polymers under different environmental conditions and selection of appropriate technique for specific combination of mixture of polymer and catalysts which helps to degrade the polymeric material.
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Xu, Yonghang, Fangya Zhou, Danmin Zhou, Jintang Mo, Huawen Hu, Limiao Lin, Jingshu Wu, Mingguang Yu, Min Zhang, and Hong Chen. "Degradation Behaviors of Biodegradable Aliphatic Polyesters and Polycarbonates." Journal of Biobased Materials and Bioenergy 14, no. 2 (April 1, 2020): 155–68. http://dx.doi.org/10.1166/jbmb.2020.1958.
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Aliphatic polyesters and polycarbonates such as polylactide (PLA), polycaprolactone (PCL) and poly(propylene carbonate) (PPC), are well known as biodegradable, biocompatible and environmental-friendly polymeric materials, which have been widely used in various areas ranging from packaging to biomedical materials. The production and usage of biodegradable plastics can greatly alleviate the safety and environmental concerns because of the fairly short degradation periods and low toxicity of catabolite. During the degradation process of polymers, obvious changes appear in polymer structures and the physiochemical properties. Therefore, it is necessary to regulate and control the degradation behaviors and periods of biodegradable plastics such as polyesters and polycarbonates, which is significant for their more widespread popularization and applications. In this context, it is highly desirable to make a review contribution in this field so as to better understand the recent research progress on polymer degradation behaviors and kinetics, as well as the future prospect of biodegradable polymers. Herein, this paper reviews the research progress on the degradation behaviors of biodegradable polyesters and polycarbonates materials including PLA, PCL and PPC. Through an in-depth study of various internal/external factors, the degradation mechanism of these polymers is unraveled, which will motivate future studies into the synthesis of novel biodegradable polymers and the understanding of their degradation behavior on the molecular level.
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Chang, L. L., D. L. Raudenbush, and S. K. Dentel. "Aerobic and anaerobic biodegradability of a flocculant polymer." Water Science and Technology 44, no. 2-3 (July 1, 2001): 461–68. http://dx.doi.org/10.2166/wst.2001.0802.
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Flocculant polymers are used to improve the efficiency of separation processes used in wastewater treatment. The subsequent fate and effects of these additives are uncertain, however, with some previous reports indicating them to be biodegradable while others indicate complete recalcitrance. The biodegradability of a common flocculant polymer was therefore evaluated, using both aerobic and anaerobic batch assays. Knowledge of the polymer's chemical composition also allowed degradation stoichiometries to be calculated for complete biodegradation and also for incomplete degradation to several hypothesized end products. Results showed conclusively that the polymer was subject to partial degradation by both aerobic and anaerobic cultures. Measured oxygen consumption under aerobic conditions, and gas production under anaerobic conditions, both indicate that the partial destruction of pendant cationic moieties occurs, but that the polymer's CH2 backbone remains essentially intact. These results allow seemingly contradictory previous reports to be explained. The findings are relevant to the environmental fate of these polymers as well as certain treatment process effects.
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He, Yuanxin, Hongyu Li, Xiang Xiao, and Xinyu Zhao. "Polymer Degradation: Category, Mechanism and Development Prospect." E3S Web of Conferences 290 (2021): 01012. http://dx.doi.org/10.1051/e3sconf/202129001012.
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With the increasing demand for polymers, white pollution has become a serious concern all around the world. The admirable degradation methods of them are desirable for overcoming this problem. In the past several decades, numerous researches on polymer degradation have been reported. This review commits to different degradation strategies of polymers and four main degradation protocols firstly, including photodegradation, oxidative degradation, catalytic degradation, and biodegradation, are demonstrated in detail. Secondly, some specific samples are discussed for each kind of degradation. Finally, the outlook and future of polymer degradation are proposed. In particular, the comprehensive comparison of different degradation methods is covered to provide the best choice for dealing with different polymers wastes. These will be beneficial to the development of processing plastic and conversion of polymer wastes.
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Zaikov, Gennady, and Marina Artsis. "Degradation of polymers in aggressive media. Kinetic approach." Chemistry & Chemical Technology 3, no. 1 (March 15, 2009): 29–40. http://dx.doi.org/10.23939/chcht03.01.029.
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The degradation of polymers in aggressive media is a complex physico-chemical process including adsorption, diffusion and the dissociation of chemically unstable bonds. The course of degradation has a number of special features, which are linked both with the specific structure of polymeric materials and with specific kinetics of reactions in solids
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Ruqaya Raad and Mustafa Abdallh. "Surface modification to enhance photo-stability of polymers." GSC Advanced Research and Reviews 11, no. 2 (May 30, 2022): 080–88. http://dx.doi.org/10.30574/gscarr.2022.11.2.0130.
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Photo-degradation is an irreversible alteration in the chemical, mechanical and physical properties of polymers, these alterations are a result of photon absorption from sunlight. UV-light is considered to be the main factor for initiating photo-degradation process of polymers. To extend the lifetime of polymers, their durability, overall minimization of the rate of photo degradation and protection of polymers against environmental factors, stabilizers are introduced to polymers. In addition, since the interaction of the polymer with its environment occurs mainly at the surface of the polymer, therefore surface modification of polymers is used to enhance the UV photo-stabilization. This method can also provide a more durable, weather resistant and photo-stable polymers.
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Ofoegbu, Stanley, Mário Ferreira, and Mikhail Zheludkevich. "Galvanically Stimulated Degradation of Carbon-Fiber Reinforced Polymer Composites: A Critical Review." Materials 12, no. 4 (February 21, 2019): 651. http://dx.doi.org/10.3390/ma12040651.
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Carbon is used as a reinforcing phase in carbon-fiber reinforced polymer composites employed in aeronautical and other technological applications. Under polarization in aqueous media, which can occur on galvanic coupling of carbon-fiber reinforced polymers (CFRP) with metals in multi-material structures, degradation of the composite occurs. These degradative processes are intimately linked with the electrically conductive nature and surface chemistry of carbon. This review highlights the potential corrosion challenges in multi-material combinations containing carbon-fiber reinforced polymers, the surface chemistry of carbon, its plausible effects on the electrochemical activity of carbon, and consequently the degradation processes on carbon-fiber reinforced polymers. The implications of the emerging use of conductive nano-fillers (carbon nanotubes and carbon nanofibers) in the modification of CFRPs on galvanically stimulated degradation of CFRP is accentuated. The problem of galvanic coupling of CFRP with selected metals is set into perspective, and insights on potential methods for mitigation and monitoring the degradative processes in these composites are highlighted.
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Doh, Jaehyeok, Sang-Woo Kim, and Jongsoo Lee. "Reliability assessment on the degradation properties of polymers under operating temperature and vibration conditions." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 232, no. 13 (October 24, 2017): 1782–98. http://dx.doi.org/10.1177/0954407017735263.
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This study focuses on the design of polymer components considering their degradation under designed operating conditions in automobiles. We use stochastic and statistical methods to ensure that such components are reliable and robust. The behaviours of polymers are described using a viscoelastic model, and degradation properties of polymers are obtained from creep and tensile data that are acquired at various temperatures. Using the Maxwell fluid model, we calculate the Prony series, which estimates viscoelastic models based on creep data. By considering Prony coefficients that describe degradation characteristics, this approach generates stress data via a frequency-response analysis of polymer components in automobiles. These data are used to generate performance functions by the response surface method. We assess the reliability considering the variation of temperature-dependent degradation properties and the areas of the peak frequency. In this study, degraded properties and frequencies are assumed to have a normal distribution, and we evaluate the reliability and probability of failure under the yield strength criteria using a Monte Carlo simulation. We then compare the reliability and failure probabilities of the given polymers in an automotive component. Based on these comparisons, we suggest the most suitable polymeric materials for use in automotive applications.
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Zhuikov, Vsevolod A., Elizaveta A. Akoulina, Dariana V. Chesnokova, You Wenhao, Tatiana K. Makhina, Irina V. Demyanova, Yuliya V. Zhuikova, et al. "The Growth of 3T3 Fibroblasts on PHB, PLA and PHB/PLA Blend Films at Different Stages of Their Biodegradation In Vitro." Polymers 13, no. 1 (December 29, 2020): 108. http://dx.doi.org/10.3390/polym13010108.
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Over the past century there was a significant development and extensive application of biodegradable and biocompatible polymers for their biomedical applications. This research investigates the dynamic change in properties of biodegradable polymers: poly(3-hydroxybutyrate (PHB), poly-l-lactide (PLA), and their 50:50 blend (PHB/PLA)) during their hydrolytic non-enzymatic (in phosphate buffered saline (PBS), at pH = 7.4, 37 °C) and enzymatic degradation (in PBS supplemented with 0.25 mg/mL pancreatic lipase). 3T3 fibroblast proliferation on the polymer films experiencing different degradation durations was also studied. Enzymatic degradation significantly accelerated the degradation rate of polymers compared to non-enzymatic hydrolytic degradation, whereas the seeding of 3T3 cells on the polymer films accelerated only the PLA molecular weight loss. Surprisingly, the immiscible nature of PHB/PLA blend (showed by differential scanning calorimetry) led to a slower and more uniform enzymatic degradation in comparison with pure polymers, PHB and PLA, which displayed a two-stage degradation process. PHB/PLA blend also displayed relatively stable cell viability on films upon exposure to degradation of different durations, which was associated with the uneven distribution of cells on polymer films. Thus, the obtained data are of great benefit for designing biodegradable scaffolds based on polymer blends for tissue engineering.
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Rizzarelli, Paola, and Marco Rapisarda. "Matrix-Assisted Laser Desorption and Electrospray Ionization Tandem Mass Spectrometry of Microbial and Synthetic Biodegradable Polymers." Polymers 15, no. 10 (May 18, 2023): 2356. http://dx.doi.org/10.3390/polym15102356.
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The in-depth structural and compositional investigation of biodegradable polymeric materials, neat or partly degraded, is crucial for their successful applications. Obviously, an exhaustive structural analysis of all synthetic macromolecules is essential in polymer chemistry to confirm the accomplishment of a preparation procedure, identify degradation products originating from side reactions, and monitor chemical–physical properties. Advanced mass spectrometry (MS) techniques have been increasingly applied in biodegradable polymer studies with a relevant role in their further development, valuation, and extension of application fields. However, single-stage MS is not always sufficient to identify unambiguously the polymer structure. Thus, tandem mass spectrometry (MS/MS) has more recently been employed for detailed structure characterization and in degradation and drug release monitoring of polymeric samples, among which are biodegradable polymers. This review aims to run through the investigations carried out by the soft ionization technique matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) and electrospray ionization mass spectrometry (ESI-MS) MS/MS in biodegradable polymers and present the resulting information.
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Lear, G., S. D. M. Maday, V. Gambarini, G. Northcott, R. Abbel, J. M. Kingsbury, L. Weaver, J. A. Wallbank, and O. Pantos. "Microbial abilities to degrade global environmental plastic polymer waste are overstated." Environmental Research Letters 17, no. 4 (March 15, 2022): 043002. http://dx.doi.org/10.1088/1748-9326/ac59a7.
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Abstract Internationally, the environmental damage caused by the improper disposal of approximately 100 Mt of plastic waste per annum is of growing concern. Attempts to address this issue have generated many hundreds of scientific studies announcing the discovery of novel plastic-degrading microorganisms and their respective enzymes. On closer inspection, however, evidence remains sparse for the microbial degradation of most of the plastic polymers produced globally. We systematically surveyed the international literature to confirm how many microorganisms proposed to degrade plastics (n = 664) cause substantial (i.e. ⩾20% mass) losses of virgin polymer, rather than losses of plastic additives, filler, and/or shedding of polymer micro-fragments. We noted where degradation was only demonstrated for artificially aged polymer since physicochemical ageing procedures increase the abundance of monomers and oligomers such that they may be degraded by microbial activity. Additionally, artificial ageing may introduce functional groups to the polymer backbone, creating more locations susceptible to microbial degradation than would otherwise occur in the environment. We identified multiple studies demonstrating the effective microbial degradation of heterochain plastic polymers such as polylactic acid, polycaprolactone and polyethylene terephthalate (i.e. polymers containing elements other than carbon in the backbone structure). However, in the literature, we find no evidence for the substantial degradation of unadulterated polyethylene, polypropylene, polystyrene or polyvinyl chloride, homochain polymers which represent the overwhelming majority of global plastics production. Current research demonstrates that the pre-treatment of plastics with elevated temperature or UV-light may speed physicochemical plastic degradation, with valuable applications for downstream microbial processing. However, evidence for the microbial degradation of most plastic polymers in current circulation is lacking. We outline simple criteria that should be met before announcing the microbial degradation of plastic polymers. We hope this may help to address largely unsubstantiated expectations that microorganisms can degrade many plastic polymers in situ.
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Visan, Anita Ioana, Gianina Popescu-Pelin, and Gabriel Socol. "Degradation Behavior of Polymers Used as Coating Materials for Drug Delivery—A Basic Review." Polymers 13, no. 8 (April 14, 2021): 1272. http://dx.doi.org/10.3390/polym13081272.
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The purpose of the work was to emphasize the main differences and similarities in the degradation mechanisms in the case of polymeric coatings compared with the bulk ones. Combined with the current background, this work reviews the properties of commonly utilized degradable polymers in drug delivery, the factors affecting degradation mechanism, testing methods while offering a retrospective on the evolution of the controlled release of biodegradable polymeric coatings. A literature survey on stability and degradation of different polymeric coatings, which were thoroughly evaluated by different techniques, e.g., polymer mass loss measurements, surface, structural and chemical analysis, was completed. Moreover, we analyzed some shortcomings of the degradation behavior of biopolymers in form of coatings and briefly proposed some solving directions to the main existing problems (e.g., improving measuring techniques resolution, elucidation of complete mathematical analysis of the different degradation mechanisms). Deep studies are still necessary on the dynamic changes which occur to biodegradable polymeric coatings which can help to envisage the future performance of synthesized films designed to be used as medical devices with application in drug delivery.
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Basan, Satılmış. "Thermal degradation of polymers and polymer blends." Hacettepe Journal of Biology and Chemistry 1, no. 42 (February 5, 2014): 143. http://dx.doi.org/10.15671/hjbc.20144210828.
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Rydz, Joanna, Marta Musiol, and Marek Kowalczuk. "Polymers Tailored for Controlled (Bio)degradation Through End-Group and In-Chain Functionalization." Current Organic Synthesis 14, no. 6 (September 28, 2017): 768–77. http://dx.doi.org/10.2174/1570179414666161115151634.
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Background: Currently, polymers can be created with specific properties that are tailored to a wide range of applications from medical to everyday products as packaging. There are different techniques to prepare novel polymer materials with various architectures and specific groups via a variety of reaction mechanisms of different complexity. End-group modification of polymers is a powerful tool for tailoring polymer properties. Objective: The review provides a brief description of the functional moieties and an outline of synthetic strategies used for tailoring the (bio)degradable polymer properties by end-group and in-chain functionalization. Conclusion: The contemporary synthetic strategies used in tailoring the (bio)degradable polymer properties by the end-group and in-chain functionalization demonstrate the importance of the relation between their subtle molecular structure, properties and function. When the development of (bio)degradable polymers is in its infancy the most crucial features are concentrated on the effect of macromolecular architecture, new monomer systems, polymerization mechanisms and different polymerization techniques on final (bio)degradable properties. Significant efforts have been directed towards the type of functional moieties and their influence on the degradation manner. Presented methods should help to design novel biodegradable polymeric materials and to avoid failures of the commercial products manufactured from them.
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Fakher, Sherif, and Abdelaziz Lafi Khlaifat. "Experimental Investigation of Polymer Injection in High Permeability Conduits for Material Sustainability and Behavior in Oil Reservoirs." Polymers 15, no. 13 (July 5, 2023): 2950. http://dx.doi.org/10.3390/polym15132950.
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Polymers are one of the most widely used chemicals in the oil and gas industry. They are used for mobility control in enhanced oil recovery, in conformance control as a cross-linked plugging agent, as a fracking fluid for fracture propagation and proppant transportation, and in drilling fluids as an additive for drilling mud enhancement. This research characterizes the polymer injectivity in different pore sizes under different conditions and evaluates the polymer conditions after injection. Based on this, the ability to reinject the polymer in the porous media is discussed. The factors studied include the pore size, the polymer concentration, the polymer injection flowrate, and polymer injectivity. When the porous media size was reduced to 1.59 mm (1/16th of an inch), the injectivity value reduced significantly, reaching less than 0.2 mL/min/psi and the polymer degradation increased primarily due to shearing. Results also showed that the polymers underwent four main degradations during injection including dehydration, syneresis, shearing, and excessive hydrolysis. In continuous fractures, the degradation is a strong function of the fracture size, length, and the polymer structure. The experimental results showed that one or more of the polymer degradations resulted in the inability to reinject the polymer in most cases.
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Rojas-Tapias, Daniel, Oriana Ortega Sierra, Diego Rivera Botía, and Ruth Bonilla. "Preservation of Azotobacter chroococcum vegetative cells in dry polymers." Universitas Scientiarum 20, no. 2 (October 10, 2014): 201. http://dx.doi.org/10.11144/javeriana.sc20-2.pacv.
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We studied the preservation of Azotobacter chroococcum C26 using three dry polymers: carrageenin, sodium alginate, and HPMC, using a method of accelerated degradation. Bacterial viability, as response variable, was measured at three temperatures in four different times, which was followed by calculation of bacterial degradation rates. Results showed that temperature, time of storage, and protective agent influenced both viability and degradation rates (P;lt;0.05). We observed, using the Arrhenius thermodynamic model, that the use of polymers increased the activation energy of bacterial degradation compared to control. We obtained thermodynamic models for each polymer, based on the Arrhenius equation, which predicted the required time for thermal degradation of the cells at different temperatures. Analysis of the models showed that carrageenin was the best polymer to preserve A. chroococcum C26 since ~ 900 days are required at 4 ºC to reduce its viability in two log units. We conclude, therefore, that long-term preservation of A. chroococcum C26 using dry polymers is suitable under adequate preservation and storage conditions.
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Ko, W. C., and R. R. Bresee. "FT-IR Microspectroscopic Study of Shot Formation in Melt-Blown Webs." Applied Spectroscopy 57, no. 6 (June 2003): 636–41. http://dx.doi.org/10.1366/000370203322005319.
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We used Fourier transform infrared (FT-IR) microspectroscopy to investigate the chemical nature of fibers and defects called “shot” in melt-blown webs. Spectral differences were observed and evaluated in light of known thermal and oxidative degradation reactions for conditions comparable to those we used for melt blowing. Three different isotactic polypropylene polymers were evaluated in terms of the amount of shot produced and the amount of oxidative degradation exhibited by fibers and shot particles from each polymer. Little oxidative degradation was observed in fibers and the amount of degradation in fibers varied little for the three polymers we evaluated. Substantially more degradation was observed in shot particles, and the amount of degradation varied among the three polymers. Compared to polymer bound for fibers, we concluded that high temperature and mechanical shear in the extruder may introduce more chain scission in polymer bound for shot particles. Autoxidation reactions may occur after melt exits the die, and our data indicated that more oxidative degradation occurred in polymer that became shot particles than polymer that became fibers. The most favorable site for oxidation seemed to be tertiary rather than methylene hydrogen. Overall, the thermal history of polymer that becomes shot particles may be significantly different than the thermal history of polymer that becomes fibers, and this difference may have influenced shot formation.
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Marmo, J. C., and K. B. Wagener. "Metathetical Degradation and Depolymerization of Unsaturated Polymers." Rubber Chemistry and Technology 70, no. 3 (July 1, 1997): 519–29. http://dx.doi.org/10.5254/1.3538439.
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Abstract The employment of transition metal catalysts has been a viable route in the degradation and depolymerization of unsaturated polymers. Initially, unsaturated polymers were degraded with a catalytic system containing a transition metal and a Lewis acid cocatalyst (WCl6/SnBu4). Degradation chemistry was effective in reducing the molecular weight of the polymer, however, the classical catalyst system induces side reactions which generates ill-defined products. These side reactions were obviated by using a preformed alkylidene without a Lewis acid cocatalyst, and perfectly difunctional telechelics were synthesized.
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Kim, Sunwoo, Youngmin Lee, Changhwan Kim, and Sunwoong Choi. "Analysis of Mechanical Property Degradation of Outdoor Weather-Exposed Polymers." Polymers 14, no. 2 (January 17, 2022): 357. http://dx.doi.org/10.3390/polym14020357.
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It is well known that many polymers are prone to outdoor weathering degradation. Therefore, to ensure the safety and integrity of the structural parts and components made from polymers for outdoor use, their weather-affected mechanical behavior needs to be better understood. In this study, the critical mechanical property for degradation was identified and modeled into a usable format for use in the virtual analysis. To achieve this, an extensive 4-year outdoor weathering test was carried out on polycarbonate (PC), polypropylene (PP), polybutylene terephthalate (PBT), and high-density polyethylene (HDPE) polymers up to a total UV irradiation of 1020 MJ/m2 at a 315~400 nm wavelength. In addition, tensile tests were performed by collecting five specimens for each material at every 60 MJ/m2 interval. With the identification of fracture strain retention as the key performance index for mechanical property degradation, a fracture strain retention function was developed using logistic regression analysis for each polymer. In addition, a method for using fracture strain retention function to establish a mechanical property degradation dataset was proposed and successfully tested by performing weathering FE analysis on the virtual automotive collision behavior of a PC part under intermittent UV irradiation doses. This work showed the potential of using fracture strain retention function to predict the performance of polymeric components undergoing mechanical property degradation upon outdoor weathering.
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Banerjee, Risav, and Trisha Bhattacharya. "Degradation of synthetic polymers: Microbial approach." Indian Journal of Microbiology Research 9, no. 1 (April 15, 2022): 9–13. http://dx.doi.org/10.18231/j.ijmr.2022.002.
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A synthetic polymer is a plastic, which is having wide applications in our day-to-day life. The packaging industries, agriculture, cosmetics, etc. Plastics are not easily degradable, it takes 1000 years to degrade a plastic or even more than that. The pollution caused by plastic is not only because of the waste disposal method but it is also because it releases carbon dioxide and dioxins while burning. Plastics are considered a threat to the environment as they are not easily degradable. Our review is based on the microbial approach for plastic degradation. The waste management method being used for plastic disposal is not effective enough. Nowadays biodegradable polymers are also being used as they are more easily degradable compared to synthetic polymers. The bacteria and fungi degrade most of the organic and inorganic components like starch, lignin, cellulose, and hemicelluloses.
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Alberti, Giancarla, Camilla Zanoni, Vittorio Losi, Lisa Rita Magnaghi, and Raffaela Biesuz. "Current Trends in Polymer Based Sensors." Chemosensors 9, no. 5 (May 13, 2021): 108. http://dx.doi.org/10.3390/chemosensors9050108.
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This review illustrates various types of polymer and nanocomposite polymeric based sensors used in a wide variety of devices. Moreover, it provides an overview of the trends and challenges in sensor research. As fundamental components of new devices, polymers play an important role in sensing applications. Indeed, polymers offer many advantages for sensor technologies: their manufacturing methods are pretty simple, they are relatively low-cost materials, and they can be functionalized and placed on different substrates. Polymers can participate in sensing mechanisms or act as supports for the sensing units. Another good quality of polymer-based materials is that their chemical structure can be modified to enhance their reactivity, biocompatibility, resistance to degradation, and flexibility.
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Krongauz, Vadim V. "Compensation effect: sublimation, diffusion in polymers, polymer degradation." Journal of Thermal Analysis and Calorimetry 138, no. 5 (October 1, 2019): 3425–44. http://dx.doi.org/10.1007/s10973-019-08851-z.
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Al-Shakry, Badar, Tormod Skauge, Behruz Shaker Shiran, and Arne Skauge. "Polymer Injectivity: Investigation of Mechanical Degradation of Enhanced Oil Recovery Polymers Using In-Situ Rheology." Energies 12, no. 1 (December 24, 2018): 49. http://dx.doi.org/10.3390/en12010049.
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Water soluble polymers have attracted increasing interest in enhanced oil recovery (EOR) processes, especially polymer flooding. Despite the fact that the flow of polymer in porous medium has been a research subject for many decades with numerous publications, there are still some research areas that need progress. The prediction of polymer injectivity remains elusive. Polymers with similar shear viscosity might have different in-situ rheological behaviors and may be exposed to different degrees of mechanical degradation. Hence, determining polymer in-situ rheological behavior is of great significance for defining its utility. In this study, an investigation of rheological properties and mechanical degradation of different partially hydrolyzed polyacrylamide (HPAM) polymers was performed using Bentheimer sandstone outcrop cores. The results show that HPAM in-situ rheology is different from bulk rheology measured by a rheometer. Specifically, shear thickening behavior occurs at high rates, and near-Newtonian behavior is measured at low rates in porous media. This deviates strongly from the rheometer measurements. Polymer molecular weight and concentration influence its viscoelasticity and subsequently its flow characteristics in porous media. Exposure to mechanical degradation by flow at high rate through porous media leads to significant reduction in shear thickening and thereby improved injectivity. More importantly, the degraded polymer maintained in-situ viscosity at low flow rates indicating that improved injectivity can be achieved without compromising viscosity at reservoir flow rates. This is explained by a reduction in viscoelasticity. Mechanical degradation also leads to reduced residual resistance factor (RRF), especially for high polymer concentrations. For some of the polymer injections, successive degradation (increased degradation with transport length in porous media) was observed. The results presented here may be used to optimize polymer injectivity.
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Charles, Julie, G. R. Ramkumaar, S. Azhagiri, and S. Gunasekaran. "FTIR and Thermal Studies on Nylon-66 and 30% Glass Fibre Reinforced Nylon-66." E-Journal of Chemistry 6, no. 1 (2009): 23–33. http://dx.doi.org/10.1155/2009/909017.
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The present study deals with the characterization of the polymeric materialsviz.,nylon-66 and 30% glass fibre reinforced nylon-66 (GF Nylon-66) by employing FTIR and thermal measurements. The complete vibrational band assignment made available for nylon-66 and GF nylon-66 using FTIR spectra confirm their chemical structure. FTIR spectroscopy provides detailed information on polymer structure through the characteristic vibrational energies of the various groups present in the molecule. The thermal behavior of nylon-66 and GF nylon-66 essential for proper processing and fabrication was studied from TGA and DTA thermograms. The thermal stability of the polymers was studied from TGA and the activation energy for the degradation of the polymeric materials was calculated using Murray-White plot and Coats-Redfern plot. The polymer with high activation energy is more thermally stable. GF nylon-66 is found to be more thermally stable than nylon-66. The major thermal transitions such as crystalline melting temperature (Tm) and degradation temperature (Td) of the polymers were detected from DTA curves. The melting behaviour of the polymer depends upon the specimen history and in particular upon the temperature of crystallization. The melting behaviour also depends upon the rate at which the specimen is heated. The various factors such as molar mass and degree of chain branching govern the value of Tmin different polymers.
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Kihara, Nobuhiro. "Development of oxidatively degradable polymeric materials that can be easily recycled and reused, reducing negative environmental impacts." Impact 2022, no. 3 (June 30, 2022): 34–36. http://dx.doi.org/10.21820/23987073.2022.3.34.
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Polymers are useful and increasingly prolific and their improper disposal is a growing problem. Diacylhydrazine can be incorporated into polymers to enhance thermal and chemical stability and may also make them oxidatively degradable, which means they can be easily and safely disposed of after use, with no environmental implications. Professor Nobuhiro Kihara, Department of Chemistry, Kanagawa University, Japan, recognised the need for a polymer that has a degradation reaction initiated by artificial stimuli, which led him to study oxidatively degradable polymers. Using diacylhydrazine, he and his team have developed a polymer that boasts attractive properties and numerous applications and benefits. The polymer maintains high strength, is weather resistant and resistant to heat, water, acid and sunlight yet is rapidly degradable when it is time to start the degradation process. This means that it can be easily and conveniently disposed of after use. It can be used in plastic, adhesive or paint and the composite materials can be separated and recycled or reused after use. The expectation is that oxidative degradation will reduce the load for the disposal of plastic and there are further opportunities to explore as there is potential for the use of various oxidant-induced degradation reactions in the design of degradable polymers, as well as artificial stimuli other than oxidation, for example electric current, to promote degradation. Kihara and the team have developed an oxidatively degradable epoxy resin that can be used as an adhesive and an oxidatively degradable SAP (superabsorbent polymer).
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Ponjavic, Marijana, Marija S. Nikolic, Sanja Stevanovic, Jasmina Nikodinovic-Runic, Sanja Jeremic, Aleksandar Pavic, and Jasna Djonlagic. "Hydrolytic degradation of star-shaped poly(ε-caprolactone)s with different number of arms and their cytotoxic effects." Journal of Bioactive and Compatible Polymers 35, no. 6 (September 3, 2020): 517–37. http://dx.doi.org/10.1177/0883911520951826.
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Star-shaped polymers of biodegradable aliphatic polyester, poly( ε-caprolactone), PCL, with different number of arms (three, four, and six) were synthesized by ring-opening polymerization initiated by multifunctional alcohols used as cores. As potential biomaterials, synthesized star-shaped poly( ε-caprolactone)s, sPCL, were thoroughly characterized in terms of their degradation under different pH conditions and in respect to their cytotoxicity. The in vitro degradation was performed in phosphate buffer (pH 7.4) and hydrochloric acid solution (pH 1.0) over 5 weeks. Degradation of sPCL films was followed by the weight loss measurements, GPC, FTIR, and AFM analysis. While the most of the samples were stable against the abiotic hydrolysis at pH 7.4 after 5 weeks of degradation, degradation was significantly accelerated in the acidic medium. Degradation rate of polymer films was affected by the polymer architecture and molecular weight. The molecular weight profiles during the degradation revealed random chain scission of the ester bonds indicating bulk degradation mechanism of hydrolysis at pH 7.4, while acidic hydrolysis proceeded through the bulk degradation associated with surface erosion, confirmed by AFM. The in vitro toxicity tests, cytotoxicity applying normal human fibroblasts (MRC5) and embryotoxicity assessment (using zebra fish model, Danio rerio), suggested those polymeric materials as suitable for biomedical application.
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Ogden, A. R. "Degradation of dental polymers." Journal of Dentistry 15, no. 4 (August 1987): 152. http://dx.doi.org/10.1016/0300-5712(87)90139-4.
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Kaczmarek, Halina, Alina Kamińska, Jolanta Kowalonek, and Aleksandra Szalla. "Accelerated Degradation of Polymers." Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals 354, no. 1 (December 2000): 421–25. http://dx.doi.org/10.1080/10587250008023634.
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Lehrle, Roy S. "Degradation of filled polymers." Polymer 33, no. 22 (January 1992): 4885. http://dx.doi.org/10.1016/0032-3861(92)90714-8.
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Smith, R. "Degradation of dental polymers." Clinical Materials 2, no. 4 (January 1987): 313. http://dx.doi.org/10.1016/0267-6605(87)90010-2.
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Devries, K. L., M. Igarashi, and F. Chao. "Molecular degradation of polymers." Journal of Polymer Science: Polymer Symposia 72, no. 1 (March 8, 2007): 111–29. http://dx.doi.org/10.1002/polc.5070720117.
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Zechner, Markus, Torsten Clemens, Ajay Suri, and Mukul M. Sharma. "Simulation of Polymer Injection Under Fracturing Conditions—An Injectivity Pilot in the Matzen Field, Austria." SPE Reservoir Evaluation & Engineering 18, no. 02 (March 23, 2015): 236–49. http://dx.doi.org/10.2118/169043-pa.
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Summary Polymer flooding leads to enhanced oil recovery by accelerating oil production and improving sweep efficiency. However, because of the higher viscosity, the injectivity of polymer solutions is of some concern and is important to understand to predict incremental oil recoveries. Achieving high polymer-injection rates is required to increase oil-production rates. In the field test performed in the Matzen field (Austria), polyacrylamide polymers were injected for the past 2 years. Coreflood experiments with these polymers showed a significant increase in apparent viscosity because of the viscoelastic properties of the polymer solutions. Also, severe degradation of the polymer solution at high flow velocities was detected. In addition to coreflood experiments, flow experiments through fractures were performed. In these experiments, shear thinning and limited degradation of the polymer solution were observed and quantified. Detailed polymer-injection simulations were conducted that included complex polymer rheology in the fractures and the matrix. The reservoir stress changes and their effects on the fractures were also taken into account as a result of cold-polymer injection. The results of the simulations matched the field data both for waterfloods and polymer-test floods. The simulations revealed two distinct phases during the injection of the polyacrylamide-polymer solution: Injection under matrix conditions in an early phase resulting in severe degradation of the polymers Injection under fracturing conditions after the formation parting pressure is reached, leading to limited degradation of the polymers The calibrated model was used to investigate the impact of polymer rheology and particle plugging on injectivity and fracture growth. The results of the field test and the simulations indicate that screening of fields for polyacrylamide-polymer projects needs to include geomechanical properties of the reservoir sand and cap/base rock in addition to the conventional parameters used in screening such as oil viscosity, water salinity, reservoir temperature, and reservoir permeability.
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Bürgermeister, Lisa, Marcus Hermann, Katalin Fehér, Catalina Molano Lopez, Andrij Pich, Julian Hannen, Felix Vogt, and Wolfgang Schulz. "Modelling pH-Optimized Degradation of Microgel-Functionalized Polyesters." Journal of Healthcare Engineering 2016 (2016): 1–8. http://dx.doi.org/10.1155/2016/8125416.
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We establish a novel mathematical model to describe and analyze pH levels in the vicinity of poly(N-vinylcaprolactam-co-acetoacetoxyethyl methacrylate-co-N-vinylimidazole) (VCL/AAEM/VIm) microgel-functionalized polymers during biodegradation. Biodegradable polymers, especially aliphatic polyesters (polylactide/polyglycolide/polycaprolactone homo- and copolymers), have a large range of medical applications including delivery systems, scaffolds, or stents for the treatment of cardiovascular diseases. Most of those applications are limited by the inherent drop of pH level during the degradation process. The combination of polymers with VCL/AAEM/VIm-microgels, which aims at stabilizing pH levels, is innovative and requires new mathematical models for the prediction of pH level evaluation. The mathematical model consists of a diffusion-reaction PDE system for the degradation including reaction rate equations and diffusion of acidic degradation products into the vicinity. A system of algebraic equations is coupled to the degradation model in order to describe the buffering action of the microgel. The model is validated against the experimental pH-monitored biodegradation of microgel-functionalized polymer foils and is available for the design of microgel-functionalized polymer components.
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Plota, Angelika, and Anna Masek. "Lifetime Prediction Methods for Degradable Polymeric Materials—A Short Review." Materials 13, no. 20 (October 12, 2020): 4507. http://dx.doi.org/10.3390/ma13204507.
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The determination of the secure working life of polymeric materials is essential for their successful application in the packaging, medicine, engineering and consumer goods industries. An understanding of the chemical and physical changes in the structure of different polymers when exposed to long-term external factors (e.g., heat, ozone, oxygen, UV radiation, light radiation, chemical substances, water vapour) has provided a model for examining their ultimate lifetime by not only stabilization of the polymer, but also accelerating the degradation reactions. This paper presents an overview of the latest accounts on the impact of the most common environmental factors on the degradation processes of polymeric materials, and some examples of shelf life of rubber products are given. Additionally, the methods of lifetime prediction of degradable polymers using accelerated ageing tests and methods for extrapolation of data from induced thermal degradation are described: the Arrhenius model, time–temperature superposition (TTSP), the Williams–Landel–Ferry (WLF) model and 5 isoconversional approaches: Friedman’s, Ozawa–Flynn–Wall (OFW), the OFW method corrected by N. Sbirrazzuoli et al., the Kissinger–Akahira–Sunose (KAS) algorithm, and the advanced isoconversional method by S. Vyazovkin. Examples of applications in recent years are given.
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Zaitoun, A., P. Makakou, N. Blin, R. S. S. Al-Maamari, A. R. R. Al-Hashmi, M. Abdel-Goad, and H. H. H. Al-Sharji. "Shear Stability of EOR Polymers." SPE Journal 17, no. 02 (April 16, 2012): 335–39. http://dx.doi.org/10.2118/141113-pa.
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Summary An experimental study of shear stability of several high-molecular-weight polymers used as mobility-control agents in EOR projects has been performed in well-controlled conditions. The shearing device was made of a capillary tube with an internal diameter (ID) of 125 μm, through which polymer solution was injected at a controlled rate. The setup enables a precise measurement of the shear rate to which the polymer macromolecule is submitted. The degradation rate was measured by the viscosity loss induced by the passage into the capillary tube. The shear rate was gradually increased up to 106 sec–1 while checking degradation rate at each stage. Different commercial EOR polymer products were submitted to the test with polyacrylamide backbone and different substitution monomer groups. All macromolecules behave as flexible coils in solution. The parameters investigated were Molecular weight (between 6 and 20×106)Nature of substitution group (acrylate, ATBS/sulfonate, nVP/ vinyl-pyrrolidone)Salinity Polymer shear degradation increases with molecular weight and salinity, but decreases with the presence of acrylate, ATBS, and nVP. All results can be interpreted in terms of chain flexibility. The highly flexible polyacrylamide homopolymer is the most sensitive to shear degradation. Introduction of acrylate groups in the polymer chain induces some stability because of the rigidity provided by charge repulsion, which vanishes in the presence of high salinity because of the screening of acrylate negative charges. ATBS and VP groups, which are larger in size, provide significant chain rigidity, and thus better shear stability. It is also shown that some very-high-molecular-weight polymers, after passing the shearing device, attain a final viscosity lower than lower-molecular-weight products with the same chemical composition. This factor has to be taken into account in the final choice of a polymer for a given field application. As a comparison, although less popular today than 2 decades ago, xanthan gum (XG), which behaves like a semirigid rod, is shown to be much less sensitive to the shear-degradation test than the coiled polyacrylamides (Sorbie 1991).
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Možíšková, Petra, Patricie Heinrichová, Martin Šedina, Martin Vala, Jan David, and Martin Weiter. "The influence of transport layers on the photodegradation stability of polymer solar cell structures." Journal of Polymer Engineering 34, no. 2 (April 1, 2014): 113–23. http://dx.doi.org/10.1515/polyeng-2013-0170.
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Abstract A light exposure degradation study of electrically active polymers – high-glass-transition-temperature poly(1,4-phenylenevinylene) (Tg-PPV); poly(3-hexylthiophene-2,5-diyl) (P3HT); and poly(2-methoxy-5-(3′-7′- dimethyloctyloxy)-1,4-phenylenevinylene) (MDMO-PPV) – in pure form and blends with [6,6]-phenyl C61-butyric acid methyl ester (PCBM) was conducted to assess the influence of the employed transport layers on the materials’ photodegradation stability. Devices were prepared on quartz glass and silicon (Si) substrates with a transport layer prepared from poly(3,4-ethylenedioxythiophene):poly(4-styrene sulfonate) (PEDOT:PSS) or titanium dioxide (TiO2). Photodegradation processes in ambient air demonstrated that the polymers were thermally stable in the dark; thus, the material deteriorations not only were caused by thermal stress, but also from light-induced processes. Degradation processes of pure polymers may be considered as fast – in the order of hours – but retardable by blending of polymers with PCBM. The deposition of polymer blends on an additional layer of PEDOT:PSS or TiO2 revealed that the polymer blends studied in this work (except for P3HT) presented higher stability against polymer chain scission when deposited onto the TiO2 layer. Kinetic analysis undertaken during this work revealed that the photodegradation processes were followed by two degradation steps. Degradation kinetics were evaluated according to a Perrin-like model for absorption assessments and according to simple exponential for emission measurements.
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Galyon, Hailey, Samuel Vibostok, Jane Duncan, Gonzalo Ferreira, Abby Whittington, Kirk Havens, Jason McDevitt, and Rebecca Cockrum. "Digestibility Kinetics of Polyhydroxyalkanoate and Poly(butylene succinate-co-adipate) after In Vitro Fermentation in Rumen Fluid." Polymers 14, no. 10 (May 21, 2022): 2103. http://dx.doi.org/10.3390/polym14102103.
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Using polyhydroxyalkanoate (PHA) materials for ruminal boluses could allow for longer sustained release of drugs and hormones that would reduce administration time and unneeded animal discomfort caused by continuous administration. The objective of this study was to determine ruminal degradability and kinetics of biodegradable polymers and blends. A proprietary PHA-based polymer, poly(butylene succinate-co-adipate) (PBSA), PBSA:PHA melt blends, and forage controls were incubated in rumen fluid for up to 240 h. Mass loss was measured after each incubation time, and digestion kinetic parameters were estimated. Thermogravimetric, differential scanning calorimetry, and intrinsic viscosity analyses were conducted on incubated samples. Generally, across treatments, mass loss was significant by 96 h with a minimum increase of 0.25% compared to 0 h but did not change thereafter. Degradation kinetics demonstrated that polymer treatments were still in the exponential degradation phase at 240 h with a maximum disappearance rate of 0.0031 %/h. Melting temperature increased, onset thermal degradation temperature decreased, and intrinsic viscosity decreased with incubation time, indicating structural changes to the polymers. Based on these preliminary findings, the first stage of degradation occurs within 24 h and PHA degrades slowly. However, further ruminal degradation studies of biodegradable polymers are warranted to elucidate maximum degradation and its characteristics.
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Lu, T., E. Solis-Ramos, Y. Yi, and M. Kumosa. "UV degradation model for polymers and polymer matrix composites." Polymer Degradation and Stability 154 (August 2018): 203–10. http://dx.doi.org/10.1016/j.polymdegradstab.2018.06.004.
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Seright, Randall S., J. Mac Seheult, and Todd Talashek. "Injectivity Characteristics of EOR Polymers." SPE Reservoir Evaluation & Engineering 12, no. 05 (October 27, 2009): 783–92. http://dx.doi.org/10.2118/115142-pa.
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Summary For applications in which enhanced-oil-recovery (EOR) polymer solutions are injected, we estimate injectivity losses (relative to water injectivity) if fractures are not open. We also consider the degree of fracture extension that may occur if fractures are open. Three principal EOR polymer properties are examined that affect injectivity:debris in the polymer,polymer rheology in porous media, andpolymer mechanical degradation. An improved test was developed to measure the tendency of EOR polymers to plug porous media. The new test demonstrated that plugging tendencies varied considerably among both partially hydrolyzed polyacrylamide (HPAM) and xanthan polymers. Rheology and mechanical degradation in porous media were quantified for a xanthan and an HPAM polymer. Consistent with previous work, we confirmed that xanthan solutions show pseudoplastic behavior in porous rock that closely parallels that in a viscometer. Xanthan was remarkably resistant to mechanical degradation, with a 0.1% xanthan solution (in seawater) experiencing only a 19% viscosity loss after flow through 102-md Berea sandstone at a pressure gradient of 24,600 psi/ft. For 0.1% HPAM in both 0.3% NaCl brine and seawater in 573-md Berea sandstone, Newtonian behavior was observed at low to moderate fluid fluxes, while pseudodilatant behavior was seen at moderate to high fluxes. No evidence of pseudoplastic behavior was seen in the porous rock, even though one solution exhibited a power-law index of 0.64 in a viscometer. For this HPAM in both brines, the onset of mechanical degradation occurred at a flux of 14 ft/d in 573-md Berea. Considering the polymer solutions investigated, satisfactory injection of more than 0.1 pore volume (PV) in field applications could only be expected for the cleanest polymers (i.e., that do not plug before 1,000 cm3/cm2 throughput), without inducing fractures (or formation parts for unconsolidated sands). Even in the absence of face plugging, the viscous nature of the solutions investigated requires that injectivity must be less than one-fifth that of water if formation parting is to be avoided (unless the injectant reduces the residual oil saturation and substantially increases the relative permeability to water). Since injectivity reductions of this magnitude are often economically unacceptable, fractures or fracture-like features are expected to open and extend significantly during the course of most polymer floods. Thus, an understanding of the orientation and growth of fractures may be crucial for EOR projects in which polymer solutions are injected. Introduction Maintaining mobility control is essential during chemical floods (polymer, surfactant, alkaline floods). Consequently, viscosification using water soluble polymers is usually needed during chemical EOR projects. Unfortunately, increased injectant viscosity could substantially reduce injectivity, slow fluid throughput, and delay oil production from flooded patterns. The objectives of this paper are to estimate injectivity losses associated with injection of polymer solutions if fractures are not open and to estimate the degree of fracture extension if fractures are open. We examine the three principal EOR polymer properties that affect injectivity:debris in the polymer,polymer rheology in porous media, andpolymer mechanical degradation. Although some reports suggest that polymer solutions can reduce the residual oil saturation below values expected for extensive waterflooding (and thereby increase the relative permeability to water), this effect is beyond the scope of this paper.
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Silva, B. J. B., A. C. S. Melo, D. S. Silva, L. V. Sousa, P. H. L. Quintela, S. L. Alencar, and A. O. S. Silva. "Thermo-catalytic degradation of PE and UHMWPE over zeolites with different pore systems and textural properties." Cerâmica 66, no. 380 (December 2020): 379–85. http://dx.doi.org/10.1590/0366-69132020663802948.
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Abstract The thermo-catalytic degradation of polyethylene (PE) and ultra-high molecular weight polyethylene (UHMWPE) was studied in the presence of zeolites (ZSM-5, ZSM-22, and ferrierite) with different pore systems and textural properties. The zeolites were physically mixed with polymers in the proportion of 30 wt% and submitted to thermogravimetric analysis at heating rates of 5, 10, 20, and 30 °C.min-1. The activation energy of the degradation process was determined using the Flynn-Wall-Ozawa method. The addition of zeolites to polymers has considerably reduced the temperature of degradation. ZSM-22 demonstrated greater efficiency in the degradation of PE because it has a smaller crystallite size, promoting a shorter diffusional path for the polymer fragments coming from the surface. Ferrierite showed a lower energy level in the degradation of UHMWPE, showing the need for synergy between the accessibility of the structure and acidity of the catalyst to promote the cracking of this polymer.
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Saberi, Abbas, Hamid Reza Bakhsheshi-Rad, Somayeh Abazari, Ahmad Fauzi Ismail, Safian Sharif, Seeram Ramakrishna, Mohammadreza Daroonparvar, and Filippo Berto. "A Comprehensive Review on Surface Modifications of Biodegradable Magnesium-Based Implant Alloy: Polymer Coatings Opportunities and Challenges." Coatings 11, no. 7 (June 22, 2021): 747. http://dx.doi.org/10.3390/coatings11070747.
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The development of biodegradable implants is certainly intriguing, and magnesium and its alloys are considered significant among the various biodegradable materials. Nevertheless, the fast degradation, the generation of a significant amount of hydrogen gas, and the escalation in the pH value of the body solution are significant barriers to their use as an implant material. The appropriate approach is able to solve this issue, resulting in a decrease the rate of Mg degradation, which can be accomplished by alloying, surface adjustment, and mechanical treatment. Surface modification is a practical option because it not only improves corrosion resistance but also prepares a treated surface to improve bone regeneration and cell attachment. Metal coatings, ceramic coatings, and permanent polymers were shown to minimize degradation rates, but inflammation and foreign body responses were also suggested. In contrast to permanent materials, the bioabsorbable polymers normally show the desired biocompatibility. In order to improve the performance of drugs, they are generally encapsulated in biodegradable polymers. This study summarized the most recent advancements in manufacturing polymeric coatings on Mg alloys. The related corrosion resistance enhancement strategies and future potentials are discussed. Ultimately, the major challenges and difficulties are presented with aim of the development of polymer-coated Mg-based implant materials.
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BROSTOW, Witold, Nonso CHETUYA, Osman GENCEL, Hee Jae HONG, Noah MENARD, and Susmitha SAYANA. "Durability of Portland Concrete Containing Polymeric Fillers and Fly Ash." Materials Science 26, no. 1 (November 8, 2019): 103–8. http://dx.doi.org/10.5755/j01.ms.26.1.21367.
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Portland concrete suffers in service brittle failure, extensive crack propagation, and wear rates increasing with time. In spite of all the effort expended, these problems persisted when we had started our project. We used several polymeric fillers and fly ash. Higher compressive moduli than the starting concrete are seen for some compositions, the highest for 5 % of one of the polymers + 5 % fly ash. The same composition has the lowest Taber abrasive wear loss. All composites show lower wear loss values than Portland concrete. After 25 days of acidic degradation in 4.0 molar aq. HCl, the starting Portland concrete suffers stronger degradation that our composites. Polymer swelling mitigates acidic degradation. Repetitive freeze-thaw cycles between 15oF and 85oF show disappearance of the deep voids present before the first cycle in our composites—but not in the Portland cement. While the use of fly ash mitigates contamination of the environment, it is the combination of fly ash with polymers which provides significantly improved properties - tribological, chemical and mechanical ones – of the Portland concrete.
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Habibu, Shehu, Norazilawati Muhamad Sarih, Nor Asrina Sairi, and Muzafar Zulkifli. "Rheological and thermal degradation properties of hyperbranched polyisoprene prepared by anionic polymerization." Royal Society Open Science 6, no. 11 (November 2019): 190869. http://dx.doi.org/10.1098/rsos.190869.
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Hyperbranched polyisoprene was prepared by anionic copolymerization under high vacuum condition. Size exclusion chromatography was used to characterize the molecular weight and branching nature of these polymers. The characterization by differential scanning calorimetry and melt rheology indicated lower T g and complex viscosity in the branched polymers as compared with the linear polymer. Degradation kinetics of these polymers was explored using thermogravimetric analysis via non-isothermal techniques. The polymers were heated under nitrogen from ambient temperature to 600°C using heating rates from 2 to 15°C min −1 . Three kinetics methods namely Friedman, Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose were used to evaluate the dependence of activation energy ( E a ) on conversion ( α ). The hyperbranched polyisoprene decomposed via multistep mechanism as manifested by the nonlinear relationship between α and E a while the linear polymer exhibited a decline in E a at higher conversions. The average E a values range from 258 to 330 kJ mol −1 for the linear, and from 260 to 320 kJ mol −1 for the branched polymers. The thermal degradation of the polymers studied involved one-dimensional diffusion mechanism as determined by Coats–Redfern method. This study may help in understanding the effect of branching on the rheological and decomposition kinetics of polyisoprene.
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Fortună, Maria E., Elena Ungureanu, Doina C. Jităreanu, Denis C. Țopa, and Valeria Harabagiu. "Effects of Hybrid Polymeric Material Based on Polycaprolactone on the Environment." Materials 15, no. 14 (July 13, 2022): 4868. http://dx.doi.org/10.3390/ma15144868.
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Polymers are of great interest in areas such as agriculture, medicine and pharmacy, the food and cosmetic industries, and the chemical and construction industries. However, many polymers are nonbiodegradable and are not environmentally friendly. They are highly resistant to degradation and therefore can lead to waste disposal problems. In recent years, the interest in the microbial degradation of polymeric materials has grown due to the desire for less waste pollution in the environment. In this study, the biodegradable polymer that was obtained by the ring-opening polymerization of ε-caprolactone (CL) using an aminopropyl-polydimethylsiloxane (APDMS) oligomer and the effects of the polymer towards the growth and development of tomato plants (Lypercosium esculentum) were investigated. The obtained product was characterized using FTIR spectroscopy, NMR spectroscopy, and energy dispersion spectroscopy (EDX) analysis, and the effects of this compound on the evolution of tomato plants (Lypercosium esculentum) were studied. We also studied the biological stability of the product by identifying some of the microorganisms that developed on the surface, given its susceptibility to biodegradation.
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Mwania, Fredrick Mulinge, Maina Maringa, and Jacobus G. van der Walt. "A review of the techniques used to characterize laser sintering of polymeric powders for use and re-use in additive manufacturing." Manufacturing Review 8 (2021): 14. http://dx.doi.org/10.1051/mfreview/2021012.
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Additive manufacturing (AM), is one of the key components of the 4th industrial revolution. Polymer laser sintering (PLS) is a subset of AM that is commonly used to process polymers, and which achieves good surface finish, good mechanical properties of finished products and for which there is no need for support structures. However, the requirements for polymeric powder for PLS are strident. Moreover, PLS subjects polymeric feed powders to high temperatures that lead to degradation of their thermal, rheological, and physical properties and is thus an impediment to their recyclability. Therefore, it is imperative to investigate the degree of polymer degradation or aging before re-using the material. This paper reviews the common techniques that are employed to characterize the suitability of polymeric powders for use and re-use in the PLS process. These include, but are not limited to, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), laser diffraction analysis, gas pycnometry, scanning electron microscopy (SEM), and melt flow index (MFI) testing.
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Wieser, Martin, Andreas Schaur, Seraphin Hubert Unterberger, and Roman Lackner. "On the Effect of Recycled Polyolefins on the Thermorheological Performance of Polymer-Modified Bitumen Used for Roofing-Applications." Sustainability 13, no. 6 (March 16, 2021): 3284. http://dx.doi.org/10.3390/su13063284.
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In order to meet the technical specifications in roofing applications, the bitumen used for this purpose is standardly modified by polymers. This, in general, allows the re-use of recycled polymer during the production of polymer-modified bitumen (PmB), simultaneously reducing the amount of polymeric waste. Recycling processes, however, may degrade or contaminate polymers, leading to reduced crystallinity and lower melting temperature. Six different recycled polyolefins (high crystallinity: iPP, HDPE; reduced crystallinity: APP, PP Copolymer; waxy polyolefins: Wax 105, Wax 115) were assessed on their suitability for roofing applications. Mixing characteristics, polymer distribution and thermo-mechanical properties of the PmB samples were determined, employing fluorescence microscopy, modulated temperature differential scanning calorimetry (MTDSC) and dynamic shear rheometry (DSR). Depending on mixing properties, two levels of polymer content (5 and 16 wt% or 16 and 30 wt%) were considered. High crystallinity polymers exhibited the biggest increase in |G*| and lowest phase angle. Reduced crystallinity polymers were more easily dispersed and showed improved |G*| and phase angle. Waxy polyolefins improved bitumen similarly to reduced crystallinity polymers and are easily dispersed. The results suggest, that a reduced crystallinity or lower melting temperature of the recycled polymers resulting from degradation or contamination may be beneficial, resulting in improved mixing behavior and a more homogeneous distribution of the polymer within the bitumen.
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Levitt, David B., Gary A. Pope, and Stephane Jouenne. "Chemical Degradation of Polyacrylamide Polymers Under Alkaline Conditions." SPE Reservoir Evaluation & Engineering 14, no. 03 (May 16, 2011): 281–86. http://dx.doi.org/10.2118/129879-pa.
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Summary Hydrolysis of polyacrylamide (PAM) -based polymers is rapid and extensive under the alkaline conditions typical of alkaline/ surfactant-polymer (ASP) flooding. Even at room temperature, significant hydrolysis occurs within 1 to 2 months in the presence of sodium carbonate. While this implies that polymers used in ASP floods will rapidly become susceptible to precipitation with divalent cations, in most cases the alkali present will be the most sensitive component to precipitation, so this may be a moot point. Also, autoretarding kinetics under alkaline conditions limit hydrolysis at 100°C, whereas complete hydrolysis occurs under neutral conditions. Furthermore, in-situ hydrolysis of initially unhydrolyzed PAM is proposed as a promising strategy for ASP floods because the injectivity of the unhyrolyzed PAM will be greater than that of hydrolyzed PAM (HPAM) because of its lower initial viscosity. The lower initial viscosity is not a disadvantage because once it has been hydrolyzed in-situ, its viscosity will increase.
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Al-Malaika, Sahar. "Polymer degradation discussion group, thermal degradation of polymers in honour of prof. Norman Grassie." Macromolecular Theory and Simulations 4, no. 2 (March 1995): 397. http://dx.doi.org/10.1002/mats.1995.040040212.
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Krauklis, Andrey E., Christian W. Karl, Iuri B. C. M. Rocha, Juris Burlakovs, Ruta Ozola-Davidane, Abedin I. Gagani, and Olesja Starkova. "Modelling of Environmental Ageing of Polymers and Polymer Composites—Modular and Multiscale Methods." Polymers 14, no. 1 (January 5, 2022): 216. http://dx.doi.org/10.3390/polym14010216.
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Service lifetimes of polymers and polymer composites are impacted by environmental ageing. The validation of new composites and their environmental durability involves costly testing programs, thus calling for more affordable and safe alternatives, and modelling is seen as such an alternative. The state-of-the-art models are systematized in this work. The review offers a comprehensive overview of the modular and multiscale modelling approaches. These approaches provide means to predict the environmental ageing and degradation of polymers and polymer composites. Furthermore, the systematization of methods and models presented herein leads to a deeper and reliable understanding of the physical and chemical principles of environmental ageing. As a result, it provides better confidence in the modelling methods for predicting the environmental durability of polymeric materials and fibre-reinforced composites.
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Tobita, Hidetaka. "Random Degradation of Branched Polymers. 1. Star Polymers." Macromolecules 29, no. 8 (January 1996): 3000–3009. http://dx.doi.org/10.1021/ma950971c.
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