Articoli di riviste: "EPOXY THERMOSETES"

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Zhang, Bao Hua, Bin Chen, Hong Xu e Yan Qing Weng. "Study on the Properties of Epoxy Thermosets Cured by ImHBPs under Lower Temperature". Advanced Materials Research 150-151 (ottobre 2010): 651–54. http://dx.doi.org/10.4028/www.scientific.net/amr.150-151.651.

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The 2-methylimidazole (Im) -terminated hyperbranched polyesters (ImHBPs) with different generations were prepared and used in diglycidyl ether of bisphenol A (DGEBA) as curing agents and tougheners in this work. It was found that the ImHBPs had better latent property than Im which indicated that the ImHBPs were proper to be used as low temperature curing agent in epoxy curing system. It was also found that the tensile strength, the flexural strength and impact strength of epoxy thermosets cured by ImHBPs under 90 were much higher than those of CYD-128/2-methylimidazole thermoset, which indicated that the ImHBPs obviously improved the mechanical properties of epoxy thermosets, and the thermoset cured by ImHBP with two generation had the best performance among the thermosets.

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Rösel, Uta, e Dietmar Drummer. "Correlation between the Flow and Curing Behavior of Hard Magnetic Fillers in Thermosets and the Magnetic Properties". Magnetism 1, n. 1 (27 novembre 2021): 37–57. http://dx.doi.org/10.3390/magnetism1010004.

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Polymer bonded magnets based on thermoplastics are economically produced by the injection molding process for applications in sensor and drive technology. Especially the lack of orientation in the edge layer, as well as the chemical resistance and the creep behavior limit the possible implementations of thermoplastic based polymer bonded magnets. However, thermoset based polymer bonded magnets have the opportunity to expand the applications by complying with the demands of the chemical industry or pump systems through to improved chemical and thermal resistance, viscosity and creep behavior of thermosets. This paper investigates the influence of hard magnetic particles on the flow and curing behavior of highly filled thermoset compounds based on an epoxy resin. The basic understanding of the behavior of those highly filled hard magnetic thermoset systems is essential for the fabrication of polymer bonded magnets based on thermosets in the injection molding process. It is shown that several factors like the crystal structure, the particle shape and size, as well as the thermal conductivity and the adherence between filler and matrix influence the flow and curing behavior of highly filled thermoset compounds based on epoxy resin. However, these influencing factors can be applied to any filler system with respect to a high filler amount in a thermoset compound, as they are based on the material behavior of particles. Further, the impact of the flow and curing behavior on the magnetic properties of polymer bonded magnets based on thermosets is shown. With that, the correlation between material based factors and magnetic properties within thermosets are portrayed.

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Rothenhäusler, Florian, e Holger Ruckdaeschel. "l-Arginine as Bio-Based Curing Agent for Epoxy Resins: Temperature-Dependence of Mechanical Properties". Polymers 14, n. 21 (3 novembre 2022): 4696. http://dx.doi.org/10.3390/polym14214696.

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The precise characterization of new bio-based thermosets is imperative for the correct assessment of their potential as matrix material in fiber-reinforced polymer composites. Therefore, the mechanical properties of diglycidyl ether of bisphenol a (DGEBA) cured with l-arginine were investigated to determine whether the bio-based thermoset possesses the required mechanical properties for application as a matrix material. The cured thermoset is called Argopox. The mixture of amino acid and epoxy resin was prepared via three-roll milling and cured in the presence of an urea-based accelerator. The tensile, compression, flexural and toughness properties of Argopox were characterized at T=−40 ∘C, 22 ∘C and 80 ∘C to determine the temperature-dependence of the thermoset’s mechanical properties in its service temperature range. The glass transition temperature Tg was analyzed via dynamic mechanical analysis (DMA) and is approximately 119 ∘C. The tensile, compression and flexural strength at 22 ∘C are about 56 MPa, 98 MPa and 85 MPa, respectively. The critical stress intensity factor KIC and fracture energy GIC at 22 ∘C are roughly 1.1 MPam0.5 and 510 Jm−, respectively. Consequently, Argopox possesses mechanical properties that reach performance levels similar to that of materials which are already used as matrix for fiber reinforced composites.

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Qian, Dan, Jiahai Zhou, Jieyuan Zheng, Jun Cao, Jintao Wan e Hong Fan. "Synthesis, Curing Behaviors and Properties of a Bio-Based Trifunctional Epoxy Silicone Modified Epoxy Thermosets". Polymers 14, n. 20 (18 ottobre 2022): 4391. http://dx.doi.org/10.3390/polym14204391.

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Tremendous effort has been focused on improving the toughness of epoxy, but the common approaches diminish the mechanical properties. In this work, a new silicone-modified trifunctional epoxy monomer SITEUP is synthesized from the hydrosilylation transformation of eugenol epoxy (EPEU) and tris-(dimethylsiloxy)phenylsilane. The chemical structures and curing kinetics of SITEUP are investigated based on 1H-NMR, 13C-NMR, MADLI-TOF-MS, and DSC analyses. SITEUP is introduced into DGEBA/IPDA systems as a functional modifier in varied loadings for toughening the resulting epoxy thermosets. The impact strength of the modified epoxy thermosets containing 20% SITEUP is 84% higher than that of the pristine epoxy thermoset and also maintains high flexural strength. Further morphology study reveals that the plastic deformation caused by siloxane segments is the key factor accounting for the enhanced toughness of the finalized epoxy thermosets. Si-O-Si segments incorporated into the thermosetting network could absorb more energy by increasing the mobility of polymer chains under external stress and led to improved thermal stability and damping characteristics. In addition, SITEUP is able to decrease the surface tension and increase the hydrophobic properties of the resultant epoxy materials.

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Ecochard, Yvan, Mélanie Decostanzi, Claire Negrell, Rodolphe Sonnier e Sylvain Caillol. "Cardanol and Eugenol Based Flame Retardant Epoxy Monomers for Thermostable Networks". Molecules 24, n. 9 (10 maggio 2019): 1818. http://dx.doi.org/10.3390/molecules24091818.

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Epoxy materials have attracted attention for many applications that require fireproof performance; however, the utilization of hazardous reagents brings about potential damage to human health. Eugenol and cardanol are renewable, harmless resources (according to ECHA) that allow the achievement of synthesis of novel phosphorylated epoxy monomers to be used as reactive flame retardants. These epoxy building blocks are characterized by 1H NMR and 31P NMR (nuclear magnetic resonance) and reacted with a benzylic diamine to give bio-based flame-retardant thermosets. Compared to DGEBA (Bisphenol A Diglycidyl Ether)-based material, these biobased thermosets differ by their cross-linking ratio, the nature of the phosphorylated function and the presence of an aliphatic chain. Eugenol has led to thermosets with higher glass transition temperatures due to a higher aromatic density. The flame-retardant properties were tested by thermogravimetric analyses (TGA), a pyrolysis combustion flow calorimeter (PCFC) and a cone calorimeter. These analyses demonstrated the efficiency of phosphorus by reducing significantly the peak heat release rate (pHRR), the total heat release (THR) and the effective heat of combustion (EHC). Moreover, the cone calorimeter test exhibited an intumescent phenomenon with the residues of phosphorylated eugenol thermosets. Lastly, the higher flame inhibition potential was highlighted for the phosphonate thermoset.

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Ménard, Raphaël, Claire Negrell-Guirao, Laurent Ferry, Rodolphe Sonnier e Ghislain David. "Synthesis of biobased phosphate flame retardants". Pure and Applied Chemistry 86, n. 11 (1 novembre 2014): 1637–50. http://dx.doi.org/10.1515/pac-2014-0703.

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Abstract An approach to prepare some biobased flame retardant (FR) compounds is presented. The adopted strategy consists in functionalizing an aromatic biobased phenolic compound, the phloroglucinol, with different phosphate groups in order to promote a charring effect. Different chlorophosphates were grafted onto phloroglucinol hydroxy groups and the functionalization of the hydroxy groups was quantitative. The synthesized biobased FR were incorporated into an epoxy matrix as additive to estimate their flame retardant properties. The influence of different parameters was studied such as the phosphorus content of the thermoset or the nature of the R group of the used phosphate P-O-R. MEB/EDX observations proved the influence of this R group on the compatibility between the FR and the matrix and its importance to obtain homogeneous thermoset. Thermogravimetric analyses of the phosphorus-containing thermosets showed a small decrease in thermal stability accompanied by a char yield almost tripled for a 3 %wP-containing thermoset compared to that of the thermoset without any FR. Pyrolysis combustion flow calorimetry was also used to evaluate the flammability of the modified epoxy thermoset. A significant decrease in peak of heat release rate and total heat released was observed compared to thermoset without FR. These results demonstrate the good flame retardant properties of these biobased phosphates in an epoxy matrix. In addition these results show the potential of the biobased phenolic compounds as raw material for flame retardants syntheses.

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Couture, Guillaume, Lérys Granado, Florent Fanget, Bernard Boutevin e Sylvain Caillol. "Limonene-Based Epoxy: Anhydride Thermoset Reaction Study". Molecules 23, n. 11 (23 ottobre 2018): 2739. http://dx.doi.org/10.3390/molecules23112739.

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The development of epoxy thermosets from renewable resources is of paramount importance in a sustainable development context. In this paper, a novel bio-based epoxy monomer derived from limonene was synthesized without epichlorohydrine and characterized. In fact, this paper depicts the synthesis of bis-limonene oxide (bis-LO). However, intern epoxy rings generally exhibit a poor reactivity and allow reaction with anhydride. Therefore, we used a reaction model with hexahydro-4-methylphthalic anhydride to compare reactivity of terminal and interepoxy functions. We also studied the influence of methyl group on intern epoxy functions. Furthermore, the influence of epoxy:anhydride stoichiometry and initiator amount was studied. These studies allow to propose an optimized formulation of bis-LO. Finally, a bis-LO-based thermoset was obtained and characterized.

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Rösel, Uta, e Dietmar Drummer. "Extension of the Application Range of Multipolar Bonded Ring Magnets by Thermosets in Comparison to Thermoplastics". Magnetism 3, n. 1 (20 marzo 2023): 71–89. http://dx.doi.org/10.3390/magnetism3010007.

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To expand the range of applications of multipolar bonded magnets based on a thermoplastic matrix, the chemical and thermal resistance has to be increased and the reduced orientation in the rapid solidified surface layer has to be overcome. To meet these requirements, the matrix of multipolar bonded magnets can be based on thermosets. This paper investigates in the magnetic properties, especially in the orientation of hard magnetic fillers, the pole accuracy and the mechanical properties of multipolar bonded ring magnets based on the hard magnetic filler strontium-ferrite-oxide and compares the possibilities of thermoplastic (polyamide)- and thermoset (epoxy resin, phenolic resin)-based matrices. It was shown that the magnetic potential of the thermoset-based material can only be fully used with further magnetization. However, the magnetic properties can be increased using thermoset-based compounds compared to thermoplastics in multipolar bonded ring magnets. Further, a model of the orientation and pole accuracy is found in terms of thermoset-based multipolar magnets. In addition, the change of the mechanical properties due to the different matrix systems was shown, with an increase in E-Modulus, Et, and a reduction in tensile strength, σm, and elongation at break, εm, in terms of thermosets compared to thermoplastics.

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Han, Xiao, Rui Chen, Mei Yang, Chuanbo Sun, Kun Wang e Yinsong Wang. "Transparent low-flammability epoxy resins using a benzoguanamine-based DOPO derivative". High Performance Polymers 34, n. 2 (13 ottobre 2021): 173–83. http://dx.doi.org/10.1177/09540083211049966.

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We successfully prepared a highly effective flame-retardant additive called hsalbenzoguanamine phosphaphenanthrene (HDPD) through salicylaldehyde and nitrogen-rich benzoguanamine. The introduction of HDPD into epoxy resin (EP) sharply enhanced the flame retardancy of EP/HDPD thermosets. The introduction of 6 wt% HDPD into EP succeeded in reaching the V-0 rating. Limited oxygen index results revealed the high flame-retarding performance of HDPD. Cone calorimeter test data revealed that heat and smoke released from EP/6 wt% HDPD thermoset were significantly restrained. In addition, EP/6 wt% HDPD thermoset demonstrated excellent transmittance and mechanical strength. The transmittance of EP/6 wt% HDPD was assessed from 520 to 800 nm. The results showed that transmittance of EP/6 wt% HDPD were nearly 90% of the control group.

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Han, Xiao, Rui Chen, Mei Yang, Chuanbo Sun, Kun Wang e Yinsong Wang. "Transparent low-flammability epoxy resins using a benzoguanamine-based DOPO derivative". High Performance Polymers 34, n. 2 (13 ottobre 2021): 173–83. http://dx.doi.org/10.1177/09540083211049966.

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Abstract (sommario):

We successfully prepared a highly effective flame-retardant additive called hsalbenzoguanamine phosphaphenanthrene (HDPD) through salicylaldehyde and nitrogen-rich benzoguanamine. The introduction of HDPD into epoxy resin (EP) sharply enhanced the flame retardancy of EP/HDPD thermosets. The introduction of 6 wt% HDPD into EP succeeded in reaching the V-0 rating. Limited oxygen index results revealed the high flame-retarding performance of HDPD. Cone calorimeter test data revealed that heat and smoke released from EP/6 wt% HDPD thermoset were significantly restrained. In addition, EP/6 wt% HDPD thermoset demonstrated excellent transmittance and mechanical strength. The transmittance of EP/6 wt% HDPD was assessed from 520 to 800 nm. The results showed that transmittance of EP/6 wt% HDPD were nearly 90% of the control group.

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Noè, Camilla, Minna Hakkarainen e Marco Sangermano. "Cationic UV-Curing of Epoxidized Biobased Resins". Polymers 13, n. 1 (28 dicembre 2020): 89. http://dx.doi.org/10.3390/polym13010089.

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Epoxy resins are among the most important building blocks for fabrication of thermosets for many different applications thanks to their superior thermo-mechanical properties and chemical resistance. The recent concerns on the environmental problems and the progressive depletion of petroleum feedstocks have drawn the research interest in finding biobased alternatives. Many curing techniques can be used to obtain the final crosslinked thermoset networks. The UV-curing technology can be considered the most environmentally friendly because of the absence of volatile organic compound (VOC) emissions and mild curing conditions. This review provides an overview of the state of the art of bio-based cationic UV-curable epoxy resins. Particular focus has been given to the sources of the bio-based epoxy monomers and the applications of the obtained products.

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Genua, Aratz, Sarah Montes, Itxaso Azcune, Alaitz Rekondo, Samuel Malburet, Bénédicte Daydé-Cazals e Alain Graillot. "Build-To-Specification Vanillin and Phloroglucinol Derived Biobased Epoxy-Amine Vitrimers". Polymers 12, n. 11 (10 novembre 2020): 2645. http://dx.doi.org/10.3390/polym12112645.

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Epoxy resins are widely used in the composite industry due to their dimensional stability, chemical resistance, and thermo-mechanical properties. However, these thermoset resins have important drawbacks. (i) The vast majority of epoxy matrices are based on non-renewable fossil-derived materials, and (ii) the highly cross-linked molecular architecture hinders their reprocessing, repairing, and recycling. In this paper, those two aspects are addressed by combining novel biobased epoxy monomers derived from renewable resources and dynamic crosslinks. Vanillin (lignin) and phloroglucinol (sugar bioconversion) precursors have been used to develop bi- and tri-functional epoxy monomers, diglycidyl ether of vanillyl alcohol (DGEVA) and phloroglucinol triepoxy (PHTE) respectively. Additionally, reversible covalent bonds have been incorporated in the network by using an aromatic disulfide-based diamine hardener. Four epoxy matrices with different ratios of epoxy monomers (DGEVA/PHTE wt%: 100/0, 60/40, 40/60, and 0/100) were developed and fully characterized in terms of thermal and mechanical properties. We demonstrate that their performances are comparable to those of commonly used fossil fuel-based epoxy thermosets with additional advanced reprocessing functionalities.

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Khatiwada, Shankar, Uwe Gohs, Ralf Lach, Gert Heinrich e Rameshwar Adhikari. "A New Way of Toughening of Thermoset by Dual-Cured Thermoplastic/Thermosetting Blend". Materials 12, n. 3 (12 febbraio 2019): 548. http://dx.doi.org/10.3390/ma12030548.

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The work aims at establishing the optimum conditions for dual thermal and electron beam curing of thermosetting systems modified by styrene/butadiene (SB)-based triblock copolymers in order to develop transparent and toughened materials. The work also investigates the effects of curing procedures on the ultimate phase morphology and mechanical properties of these thermoset–SB copolymer blends. It was found that at least 46 mol% of the epoxidation degree of the SB copolymer was needed to enable the miscibility of the modified block copolymer into the epoxy resin. Hence, an electron beam curing dose of ~50 kGy was needed to ensure the formation of micro- and nanostructured transparent blends. The micro- and nanophase-separated thermosets obtained were analyzed by optical as well as scanning and transmission electron microscopy. The mechanical properties of the blends were enhanced as shown by their impact strengths, indentation, hardness, and fracture toughness analyses, whereby the toughness values were found to mainly depend on the dose. Thus, we have developed a new route for designing dual-cured toughened micro- and nanostructured transparent epoxy thermosets with enhanced fracture toughness.

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Valášek, Petr, Jozef Žarnovský e Miroslav Müller. "Thermoset Composite on Basis of Recycled Rubber". Advanced Materials Research 801 (settembre 2013): 67–73. http://dx.doi.org/10.4028/www.scientific.net/amr.801.67.

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The paper describes the mechanical qualities of thermoset – epoxy resin filled with recycled rubber in the form of micro-particles. Such an application of waste can be regarded as material usage which should be preferred to other ways of waste handling. Micro-particles of recycled rubber affect the mechanical qualities of polymer in which they are dispersed. The paper quantifies cohesive and adhesive properties of the filled epoxy resin. Filling polymers – thermosets with waste fillers saves costs, it does not burden the environment, and it is inexpensive. The results described in this paper can lead to enlarging the application areas of recycled rubbers. As the filler, recycled rubber gained by the process of an ecological disposal of tyres by Gumoeko, s.r.o. (private limited company) was used.

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Ruiz, Quentin, Sylvie Pourchet, Vincent Placet, Laurent Plasseraud e Gilles Boni. "New Eco-Friendly Synthesized Thermosets from Isoeugenol-Based Epoxy Resins". Polymers 12, n. 1 (17 gennaio 2020): 229. http://dx.doi.org/10.3390/polym12010229.

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Epoxy resin plays a key role in composite matrices and DGEBA is the major precursor used. With the aim of favouring the use of bio resources, epoxy resins can be prepared from lignin. In particular, diglycidyl ether of isoeugenol derivatives are good candidates for the replacement of DGEBA. This article presents an effective and eco-friendly way to prepare epoxy resin derived from isoeugenol (BioIgenox), making its upscale possible. BioIgenox has been totally characterized by NMR, FTIR, MS and elemental analyses. Curing of BioIgenox and camphoric anhydride with varying epoxide function/anhydride molar ratios has allowed determining an optimum ratio near 1/0.9 based on DMA and DSC analyses and swelling behaviours. This thermoset exhibits a Tg measured by DMA of 165 °C, a tensile storage modulus at 40 °C of 2.2 GPa and mean 3-point bending stiffness, strength and strain at failure of 3.2 GPa, 120 MPa and 6.6%, respectively. Transposed to BioIgenox/hexahydrophtalic anhydride, this optimized formulation gives a thermoset with a Tg determined by DMA of 140 °C and a storage modulus at 40 °C of 2.6 GPa. The thermal and mechanical properties of these two thermosets are consistent with their use as matrices for structural or semi-structural composites.

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Ramon, Eric, Carmen Sguazzo e Pedro Moreira. "A Review of Recent Research on Bio-Based Epoxy Systems for Engineering Applications and Potentialities in the Aviation Sector". Aerospace 5, n. 4 (16 ottobre 2018): 110. http://dx.doi.org/10.3390/aerospace5040110.

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Epoxy resins are one of the most widely used thermosets in different engineering fields, due to their chemical resistance and thermo-mechanical properties. Recently, bio-based thermoset resin systems have attracted significant attention given their environmental benefits related to the wide variety of available natural resources, as well as the resulting reduction in the use of petroleum feedstocks. During the last two decades, considerable improvement on the properties of bio-sourced resins has been achieved to obtain performances comparable to petroleum-based systems. This paper reviews recent advances on new bio-based epoxy resins, derived from natural oils, natural polyphenols, saccharides, natural rubber and rosin. Particular focus has been given to novel chemical formulations and resulting mechanical properties of natural derived- epoxies, curing agents or entire systems, constituting an interesting alternative for a large variety of engineering applications, including the aviation sector. The present work is within the scope of the ECO-COMPASS project, where new bio-sourced epoxy matrixes for green composites are under investigation.

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Fortunato, Giovanni, Luca Anghileri, Gianmarco Griffini e Stefano Turri. "Simultaneous Recovery of Matrix and Fiber in Carbon Reinforced Composites through a Diels–Alder Solvolysis Process". Polymers 11, n. 6 (6 giugno 2019): 1007. http://dx.doi.org/10.3390/polym11061007.

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Efficient and comprehensive recycling of fiber-reinforced thermosets is particularly challenging, since the irreversible degradation of the matrix component is necessary in order to separate the fiber component in high purity. In this work, a new approach to fully recyclable thermoset composites is presented, based on the thermal reversibility of an epoxy-based polymer network, crosslinked through Diels–Alder (DA) chemistry. Carbon fiber composites, fabricated by compression molding, were efficiently recycled through a simple solvolysis procedure in common solvents, under mild conditions, with no catalysts. Specifically, the purity of reclaimed fibers, assessed by thermogravimetric analysis and scanning electron microscopy, was very high (>95%) and allowed successful reprocessing into second generation composites. Moreover, the dissolved matrix residues were directly employed to prepare smart, thermally healable coatings. Overall, DA chemistry has been shown to provide a convenient strategy towards circular economy of thermoset composites.

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Rothenhäusler, Florian, e Holger Ruckdaeschel. "Amino Acids as Bio-Based Curing Agents for Epoxy Resin: Correlation of Network Structure and Mechanical Properties". Polymers 15, n. 2 (11 gennaio 2023): 385. http://dx.doi.org/10.3390/polym15020385.

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Bio-based alternatives for petroleum-based thermosets are crucial for implementing sustainable practices in fiber-reinforced polymer composites. Therefore, the mechanical properties of diglycidyl ether of bisphenol a (DGEBA) cured with either l-arginine, l-citrulline, γ-aminobutyric acid, l-glutamine, l-tryptophan, or l-tyrosine were investigated to determine the potential of amino acids as bio-based curing agents for epoxy resins. Depending on the curing agent, the glass transition temperature, Young’s modulus, tensile strength, and critical stress intensity factor range from 98.1 ∘C to 188.3 ∘C, 2.6 GPa to 3.5 GPa, 39.4 MPa to 46.4 MPa, and 0.48 MPam0.5 to 1.34 MPam0.5, respectively. This shows that amino acids as curing agents for epoxy resins result in thermosets with a wide range of thermo-mechanical properties and that the choice of curing agent has significant influence on the thermoset’s properties. After collecting the results of dynamic mechanical analysis (DMA), tensile, flexural, compression, and compact tension tests, the functionality f, cross-link density νC, glass transition temperature Tg, Young’s modulus ET, compression yield strength σCy, critical stress intensity factor in mode I KIC, fracture energy GIC, and diameter of the plastic zone dp are correlated with one another to analyze their inter-dependencies. Here, the cross-link density correlates strongly positively with Tg, ET, and σCy, and strongly negatively with KIC, GIC, and dp. This shows that the cross-link density of DGEBA cured with amino acids has a crucial influence on their thermo-mechanical properties and that the thermosets considered may either be stiff and strong or tough, but hardly both at the same time.

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Zhang, Bao Hua, Jun Dan Ye, Bin Chen e Yan Qing Weng. "Influence of Curing Process on the Performance of Epoxy Thermosets". Advanced Materials Research 79-82 (agosto 2009): 2175–78. http://dx.doi.org/10.4028/www.scientific.net/amr.79-82.2175.

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The performance of epoxy thermosets was greatly influenced by the curing agent and curing temperature. It was known that epoxy thermosets cured under high temperature would have high normal forces which could cause fracture of the structure and then decrease the mechanical properties of the material. It was accepted that epoxy curing system should be cured under low temperature with the thermosets had the same properties as those cured under high temperature. It was important to choose proper curing agent to reach the above goal. Latent epoxy curing agent whose main component was the hyperbranched polyester (HBP) with tertiary amine as the end group was prepared and was used to diglycidyl ether of bisphenol A (DGEBA) in this work. The properties such as tensile intensity, bending intensity, impact resistance and dynamic mechanic properties of the resulting epoxy thermosets were evaluated. It was found that the resulting epoxy thermosets cured under low temperature had better mechanical properties than those cured under high temperature. The latent epoxy curing agent whose main component was the hyperbranched polyester with tertiary amine as the end group was adaptive to be used in the epoxy base of composite.

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Deringer, Tim, Christian Gröschel e Dietmar Drummer. "Influence of mold temperature and process time on the degree of cure of epoxy-based materials for thermoset injection molding and prepreg compression molding". Journal of Polymer Engineering 38, n. 1 (26 gennaio 2018): 73–81. http://dx.doi.org/10.1515/polyeng-2016-0409.

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Abstract A new hybrid process for fiber-reinforced plastics based on thermosets combining master-forming and forming in one tool is currently undergoing development. The advantage of this technique is the integrated forming and overmolding of a thermoset-based continuous fiber-reinforced sheet in one step. Although both components are epoxy based, the resin formulations slightly differ and thus require individual curing parameters. For successful combination into one process, it is essential to investigate both components in relation to the processing parameters and their influence on the degree of cure. Besides the influence on the forming and filling behavior, the degree of cure also has an effect on the resulting mechanical properties. In this investigation, the influence of curing time and temperature on the degree of cure of epoxy-based materials was investigated with regard to identifying a process window for a process combination of master-forming and forming.

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Henry, Michael M., Stephen Thomas, Mone’t Alberts, Carla E. Estridge, Brittan Farmer, Olivia McNair e Eric Jankowski. "General-Purpose Coarse-Grained Toughened Thermoset Model for 44DDS/DGEBA/PES". Polymers 12, n. 11 (30 ottobre 2020): 2547. http://dx.doi.org/10.3390/polym12112547.

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The objective of this work is to predict the morphology and material properties of crosslinking polymers used in aerospace applications. We extend the open-source dybond plugin for HOOMD-Blue to implement a new coarse-grained model of reacting epoxy thermosets and use the 44DDS/DGEBA/PES system as a case study for calibration and validation. We parameterize the coarse-grained model from atomistic solubility data, calibrate reaction dynamics against experiments, and check for size-dependent artifacts. We validate model predictions by comparing glass transition temperatures measurements at arbitrary degree of cure, gel-points, and morphology predictions against experiments. We demonstrate for the first time in molecular simulations the cure-path dependence of toughened thermoset morphologies.

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Borchardt, John K. "Tougher epoxy thermosets". Materials Today 7, n. 5 (maggio 2004): 12. http://dx.doi.org/10.1016/s1369-7021(04)00224-x.

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Engelmann, Gunnar, e Johannes Ganster. "Bio-based epoxy resins with low molecular weight kraft lignin and pyrogallol". Holzforschung 68, n. 4 (1 maggio 2014): 435–46. http://dx.doi.org/10.1515/hf-2013-0023.

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Abstract A low-molecular lignin fraction (L) was extracted for the preparation of bio-based epoxy resins. Various compositions with the “green” 1,3-glycerol diglycidyl ether (1) and the co-component pyrogallol (2) were tested. In a first series of experiments, thermosets consisting of 1 and L, were studied with respect to variable lignin contents between 20 and 50%. The best thermoset has a tensile strength of 37 MPa and a Young’s modulus of 2.2 GPa at 40% lignin input. Secondly, lignin-free compositions of 1 and 2 were prepared. For a molar fraction of the functional groups (nOH nEpoxy-1) of 130%, the tensile strength could be enhanced to 93 MPa and the modulus reached 3.7 GPa. Finally, systems with all three components were examined. The best mechanical performance of the corresponding neat thermosets was reached at nOH nEpoxy-1 of 130%. Tensile strength decreases slightly to 86 MPa and Young’s modulus remains nearly unchanged at 3.2 GPa. Two resin compositions, L+1 and L+1+2, were tested for the preparation of unidirectional composites reinforced with man-made cellulosic fibers (50% by vol.). The bending strength was 208 MPa in combination with a bending modulus of 12.5 GPa.

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Barabanova, Anna I., Egor S. Afanas’ev, Vyacheslav S. Molchanov, Andrey A. Askadskii e Olga E. Philippova. "Unmodified Silica Nanoparticles Enhance Mechanical Properties and Welding Ability of Epoxy Thermosets with Tunable Vitrimer Matrix". Polymers 13, n. 18 (9 settembre 2021): 3040. http://dx.doi.org/10.3390/polym13183040.

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Abstract (sommario):

Epoxy/silica thermosets with tunable matrix (vitrimers) were prepared by thermal curing of diglycidyl ether of bisphenol A (DGEBA) in the presence of a hardener—4-methylhexahydrophthalic anhydride (MHHPA), a transesterification catalyst—zinc acetylacetonate (ZAA), and 10–15 nm spherical silica nanoparticles. The properties of the resulting material were studied by tensile testing, thermomechanical and dynamic mechanical analysis. It is shown that at room temperature the introduction of 5–10 wt% of silica nanoparticles in the vitrimer matrix strengthens the material leading to the increase of the elastic modulus by 44% and the tensile stress by 25%. Simultaneously, nanoparticles enhance the dimensional stability of the material since they reduce the coefficient of thermal expansion. At the same time, the transesterification catalyst provides the thermoset with the welding ability at heating, when the chain exchange reactions are accelerated. For the first time, it was shown that the silica nanoparticles strengthen welding joints in vitrimers, which is extremely important, since it allows to repeatedly use products made of thermosets and heal defects in them. Such materials hold great promise for use in durable protective coatings, adhesives, sealants and many other applications.

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25

Mei, Honggang, Huaming Wang, Lei Li e Sixun Zheng. "Generation of One-Dimensional Fibrous Polyethylene Nanocrystals in Epoxy Thermosets". Polymers 14, n. 18 (19 settembre 2022): 3921. http://dx.doi.org/10.3390/polym14183921.

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Abstract (sommario):

The one-dimensional (1D) polyethylene (PE) nanocrystals were generated in epoxy thermosets via crystallization-driven self-assembly. Toward this end, an ABA triblock copolymer composed of PE midblock and poly(ε-caprolactone) (PCL) endblocks was synthesized via the ring opening metathesis polymerization followed by hydrogenation approach. The nanostructured thermosets were obtained via a two-step curing approach, i.e., the samples were cured first at 80 °C and then at 150 °C. Under this condition, the one-dimensional (1D) fibrous PE microdomains with the lengths up to a couple of micrometers were created in epoxy thermosets. In contrast, only the spherical PE microdomains were generated while the thermosets were cured via a one-step curing at 150 °C. By the use of the triblock copolymer, the generation of 1D fibrous PE nanocrystals is attributable to crystallization-driven self-assembly mechanism whereas that of the spherical PE microdomains follows traditional self-assembly mechanism. Compared to the thermosets containing the spherical PE microdomains, the thermosets containing the 1D fibrous PE nanocrystals displayed quite different thermal and mechanical properties. More importantly, the nanostructured thermosets containing the 1D fibrous PE nanocrystals displayed the fracture toughness much higher than those only containing the spherical PE nanocrystals; the KIC value was even three times as that of control epoxy.

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26

Santiago, David, e Àngels Serra. "Enhancement of Epoxy Thermosets with Hyperbranched and Multiarm Star Polymers: A Review". Polymers 14, n. 11 (30 maggio 2022): 2228. http://dx.doi.org/10.3390/polym14112228.

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Abstract (sommario):

Hyperbranched polymers and multiarm star polymers are a type of dendritic polymers which have attracted substantial interest during the last 30 years because of their unique properties. They can be used to modify epoxy thermosets to increase their toughness and flexibility but without adversely affecting other properties such as reactivity or thermal properties. In addition, the final properties of materials can be tailored by modifying the structure, molecular weight, or type of functional end-groups of the hyperbranched and multiarm star polymers. In this review, we focus on the modification of epoxy-based thermosets with hyperbranched and multiarm star polymers in terms of the effect on the curing process of epoxy formulations, thermal, mechanical, and rheological properties, and their advantages in fire retardancy on the final thermosets.

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27

Mohajeri, S., MJ Zohuriaan-Mehr e S. Pazokifard. "Epoxy matrix toughness improvement via reactive bio-resin alloying". High Performance Polymers 29, n. 7 (6 luglio 2016): 772–84. http://dx.doi.org/10.1177/0954008316656743.

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Abstract (sommario):

A facile solvent-less approach to toughen epoxy thermosets by means of a bio-based resin, that is, poly(furfuryl alcohol) (PFA; furan resin) is reported. The bio-resin PFA was firstly synthesized through polycondensation reaction of furfuryl alcohol as a bio-monomer and maleic anhydride as a catalyst. Different amounts of PFA were blended with diglycidyl ether of bisphenol A epoxy resin and cured by diethylenetriamine as a hardener, which simultaneously cross-linked both of the epoxy and PFA resins. The curing process was studied by Furrier transform infrared spectroscopy and differential scanning calorimetry. Scanning electron microscopy of the chemically cured blends revealed no phase separation. It was found remarkable increase in flexural modulus and strength of the neat and modified epoxies with increasing PFA content up to around 15%. Moreover, in comparison with neat epoxy, the epoxy-PFA thermosets showed 60% increase in critical stress intensity factor and 123% increase in critical strain energy release rate. In fact, chemical reaction of PFA-incorporated epoxy could toughen the epoxy matrix without sacrificing the flexural strength and modulus. Toughening was obtained through cross-link density reduction. As exhibited by dynamic mechanical thermal analysis, Tan δ and magnitude of β-relaxation were also increased for the epoxy-PFA alloys. Overall, this green, simple, concise and cost-effective approach was suggested for being considered to produce toughened epoxy thermosets in industrial scale.

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28

Giebler, Michael, Simone Radl, Thomas Ules, Thomas Griesser e Sandra Schlögl. "Photopatternable Epoxy-Based Thermosets". Materials 12, n. 15 (24 luglio 2019): 2350. http://dx.doi.org/10.3390/ma12152350.

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Abstract (sommario):

The present work provides a comparative study on the photopatterning of epoxy-based thermosets as a function of network structure and network mobility. Local switching of solubility properties by light of a defined wavelength is achieved by exploiting versatile o-nitrobenzyl ester (o-NBE) chemistry. o-NBE derivatives with terminal epoxy groups are synthetized and thermally cured with different types of cycloaliphatic anhydrides via nucleophilic ring opening reaction. By varying the structure of the anhydride, glass transition temperature (Tg) and surface hardness are adjusted over a broad range. Once the network has been formed, the photolysis of the o-NBE groups enables a well-defined degradation of the 3D network. Fourier transform infrared (FT-IR) spectroscopy studies demonstrate that cleavage rate and cleavage yield increase with rising mobility of the network, which is either facilitated by inherent network properties (Tg below room temperature) or a simultaneous heating of the thermosets above their Tg. The formation of soluble species is evidenced by sol-gel analysis, revealing that low-Tg networks are prone to secondary photoreactions at higher exposure doses, which lead to a re-crosslinking of the cleaved polymer chains. The change in solubility properties is exploited to inscribe positive tone micropatterns within the thermosets by photolithographic techniques. Contrast curves show that the resist performance of rigid networks is superior to flexible ones, with a contrast of 1.17 and a resolution of 8 µm.

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29

Giamberjni, M., E. Amendola e C. Carfagna. "Liquid Crystalline Epoxy Thermosets". Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals 266, n. 1 (giugno 1995): 9–22. http://dx.doi.org/10.1080/10587259508033628.

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30

Shao, Shih Wei, Chien Han Chen, Jian Ren Chan, Tzong Yuan Juang, Mahdi M. Abu-Omar e Ching Hsuan Lin. "Full atom-efficiency transformation of wasted polycarbonates into epoxy thermosets and the catalyst-free degradation of the thermosets for environmental sustainability". Green Chemistry 22, n. 14 (2020): 4683–96. http://dx.doi.org/10.1039/d0gc01318h.

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Abstract (sommario):

We report a strategy for transforming wasted polycarbonates into epoxy thermosets and degrading the thermosets with 1-hexylamine in a catalyst-free aminolysis process for environmental sustainability.

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31

Chen, Chien-Han, Shih-Huang Tung, Ru-Jong Jeng, Mahdi M. Abu-Omar e Ching-Hsuan Lin. "A facile strategy to achieve fully bio-based epoxy thermosets from eugenol". Green Chemistry 21, n. 16 (2019): 4475–88. http://dx.doi.org/10.1039/c9gc01184f.

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32

Rösel, Uta, e Dietmar Drummer. "Correlation between the Material System and the Magnetic Properties in Thermoset-Based Multipolar Ring Magnets". Magnetism 3, n. 3 (14 agosto 2023): 226–44. http://dx.doi.org/10.3390/magnetism3030018.

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Abstract (sommario):

Multipolar bonded magnets based on thermosets offer the opportunity to expand the applications of bonded magnets with respect to an increasing chemical and thermal resistance compared to thermoplastics. To utilise this option, the correlation between the material system and the magnetic properties must be explored amongst other influencing factors. This paper investigates the magnetic properties and the orientation of thermoset- (epoxy resin and phenolic resin) based bonded ring magnets with a hard magnetic filler of strontium-ferrite-oxide. The influence of the matrix material and the filler grade on the magnetic properties is correlated with the material characterisation showing a high impact of the embedding of the fillers into the matrix on the orientation and with that the magnetic properties. Based on a network theory, it can be justified that the magnetic properties can be increased due to a phenolic resin and a high filler grade. Further, it was shown that the orientation along the sample depth is highly affected by the strength of the outer magnetic field and limited in terms of the high-tool temperature in a thermoset-based production. With that, the sample depth, which reveals a proper orientation, is restricted so far.

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33

Santiago, David, Dailyn Guzmán, Xavier Ramis, Francesc Ferrando e Àngels Serra. "New Epoxy Thermosets Derived from Clove Oil Prepared by Epoxy-Amine Curing". Polymers 12, n. 1 (27 dicembre 2019): 44. http://dx.doi.org/10.3390/polym12010044.

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Abstract (sommario):

New thermosets from a triglycidyl eugenol derivative (3EPOEU) as a renewable epoxy monomer were obtained by an epoxy-amine curing process. A commercially-available Jeffamine® and isophorone diamine, both obtained from renewable resources, were used as crosslinking agents, and the materials obtained were compared with those obtained from a standard diglycidylether of bisphenol A (DGEBA). The evolution of the curing process was studied by differential scanning calorimetry and the materials obtained were characterized by means of calorimetry, thermogravimetry, thermodynamomechanical analysis, stress–strain tests and microindentation. 3EPOEU formulations were slightly less reactive, and the thermosets obtained showed higher Tgs than those prepared from DGEBA, since they had higher crosslinking density than formulations with DGEBA because of the more compact structure and higher functionality of the eugenol derivative. 3EPOEU thermosets showed good thermal stability and mechanical properties. The results obtained in this study allow us to conclude that the triglycidyl derivative of eugenol, 3EPOEU, is a safe and environmentally friendly alternative to DGEBA.

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34

Vini, R., S. Thenmozhi e SC Murugavel. "Synthesis, characterization and thermal degradation kinetics of azomethine-based halogen-free flame-retardant polyphosphonates". High Performance Polymers 31, n. 1 (18 gennaio 2018): 86–96. http://dx.doi.org/10.1177/0954008317752073.

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Abstract (sommario):

In this study, azomethine polyphosphonates were synthesized by solution polycondensation of phenylphosphonic dichloride with various azomethine diols such as [4-(4-hydroxy phenyl) iminomethyl] phenol, [(4-(4-hydroxy-3-methoxy phenyl) iminomethyl)] phenol and [4-(4-hydroxy-3-ethoxy phenyl) iminomethyl] phenol using triethylamine catalyst at ambient temperature. The structure of the synthesized polymers was confirmed by Fourier transform infrared and 1H-, 13C- and 31P- nuclear magnetic resonance spectroscopic techniques. Thermal properties of the polymers were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry under nitrogen atmosphere. The TGA data showed that the synthesized polyphosphonates produce high char yield at 600°C due to the presence of phosphorous atom in the polymer chain and hence have good flame-retardant properties. One of the synthesized polyphosphonate was blended with commercial diglycidyl ether of bisphenol-A (DGEBA) resin in various weight percentage and cured with commercial curing agent triethylene tetramine (TETA). The polyphosphonates-blended epoxy thermosets have tensile strength in the range of 5–41 MPa and the percentage of elongation at breaks was 4–18. It was found that the incorporation of polyphosphonates into epoxy thermoset decreased the tensile strength from 41 MPa to 5 MPa, whereas the elongation at break value increased with increase in the weight percentage of polyphosphonate. The influence of polyphosphonates on the flame retardancy of blended thermosets was examined by limiting oxygen index (LOI) and vertical burning (UL-94) tests and found that the polymer samples achieved an increased UL-94 rating and the LOI values were in the range of 24–26. Broido and Horowitz–Metzger methods have been used to study the thermal degradation kinetic parameters.

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35

Liu, Ren, Xiaopeng Zhang, Shuai Gao, Xiaoya Liu, Zhen Wang e Jingling Yan. "Bio-based epoxy-anhydride thermosets from six-armed linoleic acid-derived epoxy resin". RSC Advances 6, n. 58 (2016): 52549–55. http://dx.doi.org/10.1039/c6ra09077j.

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Abstract (sommario):

A series of bio-based epoxy-anhydride thermosets with considerably high thermal and mechanical properties were developed from 4-methyl hexahydrophthalic anhydride and six-armed linoleic-acid-derived epoxy resin.

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36

Hamciuc, Corneliu, Tăchiță Vlad-Bubulac, Diana Serbezeanu, Ana-Maria Macsim, Gabriela Lisa, Ion Anghel e Ioana-Emilia Şofran. "Thermal Properties and Flammability Characteristics of a Series of DGEBA-Based Thermosets Loaded with a Novel Bisphenol Containing DOPO and Phenylphosphonate Units". Materials 15, n. 21 (6 novembre 2022): 7829. http://dx.doi.org/10.3390/ma15217829.

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Abstract (sommario):

Despite a recent sustained preoccupation for developing biobased epoxies with enhanced applicability, such products have not been widely accepted for industry because of their inferior characteristics compared to classic petroleum-based epoxy thermosets. Therefore, significant effort is being made to improve the flame retardance of the most commonly used epoxies, such as diglycidyl ether-based bisphenol A (DGEBA), bisphenol F (DGEBF), novalac epoxy, and others, while continuously avoiding the use of hazardous halogen-containing flame retardants. Herein, a phosphorus-containing bisphenol, bis(4-(((4-hydroxyphenyl)amino)(6-oxido-6H-dibenzo[c,e][1,2]oxaphosphinin-6-yl)methyl)phenyl) phenylphosphonate (BPH), was synthesized by reacting bis(4-formylphenyl)phenylphosphonate with 4-hydroxybenzaldehyde followed by the addition of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) to the resulting azomethine groups. Environmentally friendly epoxy-based polymer thermosets were prepared by using epoxy resin as polymer matrix and a mixture of BPH and 4,4′-diaminodiphenylsulfone (DDS) as hardeners. A hyperbranched phthalocyanine polymer (HPc) and BaTiO3 nanoparticles were incorporated into epoxy resin to improve the characteristics of the final products. The structure and morphology of epoxy thermosets were evaluated by infrared spectroscopy and scanning electron microscopy (SEM), while the flammability characteristics were evaluated by microscale combustion calorimetry. Thermal properties were determined by thermogravimetric analysis and differential scanning calorimetry. The surface morphology of the char residues obtained by pyrolysis was studied by SEM analysis.

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37

Ferrari, Francesca, Carola Esposito Corcione, Raffaella Striani, Lorena Saitta, Gianluca Cicala e Antonio Greco. "Fully Recyclable Bio-Based Epoxy Formulations Using Epoxidized Precursors from Waste Flour: Thermal and Mechanical Characterization". Polymers 13, n. 16 (18 agosto 2021): 2768. http://dx.doi.org/10.3390/polym13162768.

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Abstract (sommario):

Organic wastes represent an increasing pollution problem due to the exponential growth of their presence in the waste stream. Among these, waste flour cannot be easily reused by transforming it into high-value-added products. Another major problem is represented by epoxy-based thermosets, which have wide use but also poor recyclability. The object of the present paper is, therefore, to analyze both of these problems and come up with innovative solutions. Indeed, we propose a completely new approach, aimed at reusing the organic waste flour, by converting it into high-value epoxy-based thermosets that could be fully recycled into a reusable plastic matrix when added to the waste epoxy-based thermosets. Throughout the research activity, the organic waste was transformed into an epoxidized prepolymer, which was then mixed with a bio-based monomer cured with a cleavable ammine. The latter reactant was based on Recyclamine™ by Connora Technologies, and in this paper, we demonstrate that this original approach could work with the synthetized epoxy prepolymers derived from the waste flour. The cured epoxies were fully characterized in terms of their thermal, rheological, and flexural properties. The results obtained showed optimal recyclability of the new resin developed.

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38

Mora, Tayouo, Boutevin, David e Caillol. "Synthesis of Pluri-Functional Amine Hardeners from Bio-Based Aromatic Aldehydes for Epoxy Amine Thermosets". Molecules 24, n. 18 (9 settembre 2019): 3285. http://dx.doi.org/10.3390/molecules24183285.

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Abstract (sommario):

Most of the current amine hardeners are petro-sourced and only a few studies have focused on the research of bio-based substitutes. Hence, in an eco-friendly context, our team proposed the design of bio-based amine monomers with aromatic structures. This work described the use of the reductive amination with imine intermediate in order to obtain bio-based pluri-functional amines exhibiting low viscosity. The effect of the nature of initial aldehyde reactant on the hardener properties was studied, as well as the reaction conditions. Then, these pluri-functional amines were added to petro-sourced (diglycidyl ether of bisphenol A, DGEBA) or bio-based (diglycidyl ether of vanillin alcohol, DGEVA) epoxy monomers to form thermosets by step growth polymerization. Due to their low viscosity, the epoxy-amine mixtures were easily homogenized and cured more rapidly compared to the use of more viscous hardeners (<0.6 Pa s at 22 °C). After curing, the thermo-mechanical properties of the epoxy thermosets were determined and compared. The isophthalatetetramine (IPTA) hardener, with a higher number of amine active H, led to thermosets with higher thermo-mechanical properties (glass transition temperatures (Tg and Tα) were around 95 °C for DGEBA-based thermosets against 60 °C for DGEVA-based thermosets) than materials from benzylamine (BDA) or furfurylamine (FDA) that contained less active hydrogens (Tg and Tα around 77 °C for DGEBA-based thermosets and Tg and Tα around 45 °C for DGEVA-based thermosets). By comparing to industrial hardener references, IPTA possesses six active hydrogens which obtain high cross-linked systems, similar to industrial references, and longer molecular length due to the presence of two alkyl chains, leading respectively to high mechanical strength with lower Tg.

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39

Serra, Angels, Xavier Ramis e Xavier Fernández-Francos. "Epoxy Sol-Gel Hybrid Thermosets". Coatings 6, n. 1 (3 febbraio 2016): 8. http://dx.doi.org/10.3390/coatings6010008.

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40

Huang, Chih-Feng, Wen-Hua Chen, Junko Aimi, Yi-Shen Huang, Sathesh Venkatesan, Yeo-Wan Chiang, Shih-Hung Huang, Shiao-Wei Kuo e Tao Chen. "Synthesis of well-defined PCL-b-PnBA-b-PMMA ABC-type triblock copolymers: toward the construction of nanostructures in epoxy thermosets". Polymer Chemistry 9, n. 48 (2018): 5644–54. http://dx.doi.org/10.1039/c8py01357h.

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41

Zweifel, Lucian, Klaus Ritter e Christian Brauner. "The Mechanical Characterization of Welded Hybrid Joints Based on a Fast-Curing Epoxy Composite with an Integrated Phenoxy Coupling Layer". Materials 15, n. 3 (8 febbraio 2022): 1264. http://dx.doi.org/10.3390/ma15031264.

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Abstract (sommario):

The joining of composites mostly relies on traditional joining technologies, such as film or paste adhesives, or mechanical fasteners. This study focuses on the appealing approach of using standard thermoplastic welding processes to join thermosets. To achieve this, a thermoplastic coupling layer is created by curing with a thermoset composite part. This leads to a functional surface that can be utilized with thermoplastic welding methods. The thermoplastic coupling layer is integrated as a thin film, compatible with the thermoset resin in the sense that it can partially diffuse in a controlled way into the thermoset resin during the curing cycle. Recent studies showed the high affinity for the interphase formation of poly hydroxy ether (phenoxy) film as coupling layer, in combination with a fast-curing epoxy system that cures within 1 min at 140 °C. In this study, an investigation based on resistance and ultrasonic welding techniques with different testing conditions of single-lap shear samples (at room temperature, 60 °C, and 80 °C) was performed. The results showed strong mechanical strengths of 28.9 MPa (±0.7%) for resistance welding and 24.5 MPa (±0.1%) for ultrasonic welding, with only a minor reduction in mechanical properties up to the glass transition temperature of phenoxy (90 °C). The combination of a fast-curing composite material with an ultra-fast ultrasonic joining technology clearly demonstrates the high potential of this joining technique for industrial applications, such as automotive, sporting goods, or wind energy. The innovation allowing structural joining performance presents key advantages versus traditional methods: the thermoplastic film positioning in the mold can be automated and localized, joint formation requires only a fraction of a second, and the joining operation does not require surface preparation/cleaning or structure deterioration (drilling).

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42

Mauro, Chiara Di, Aratz Genua e Alice Mija. "Building thermally and chemically reversible covalent bonds in vegetable oil based epoxy thermosets. Influence of epoxy–hardener ratio in promoting recyclability". Materials Advances 1, n. 6 (2020): 1788–98. http://dx.doi.org/10.1039/d0ma00370k.

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43

Fache, M., B. Boutevin e S. Caillol. "Epoxy thermosets from model mixtures of the lignin-to-vanillin process". Green Chemistry 18, n. 3 (2016): 712–25. http://dx.doi.org/10.1039/c5gc01070e.

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44

Yi, Liang, Zhixiong Huang, Cao Yu, Yongli Peng e Xinglong Liu. "Synthesis of a 9,10-dihydro-9-oxo-10phosphaphenanthrene-10-oxide-based reactive flame-retardant curing agent". Materials Express 10, n. 9 (30 settembre 2020): 1470–76. http://dx.doi.org/10.1166/mex.2020.1763.

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Abstract (sommario):

This paper aims to prepare a new curing agent, reactive flame retardant (DTF), through one-pot synthesis of 9,10-Dihydro-9-oxo-10-phosphaphenanthrene-10-oxide (DOPO), formaldehyde and triacetonediamine for Epoxy resin (EP). This new DTF was successful prepared through Fourier-transform infrared, 1H NMR, and 31P NMR spectroscopy. The flame-retardant epoxy thermoset was prepared using the 4′4-diaminodiphenylmethane (DDM) as a co-curing agent. The analysis results using the differential scanning calorimetry (DSC) showed that DTF can cure EP and improve the carbon residue yield of epoxy thermoset after burning. It observed that if the content of phosphorus was 1.0 wt%, the limiting oxygen index (LOI) of EP/DDM/DPT-4 was 30.4%, and UL94 reached the V-0 rating. The highest tensile property of the epoxy thermoset reached 98.56 MPa (P content = 0.5%), whereas the highest flexural property reached 137.28 MPa (P content = 0.75%), and the highest impact property reached 24.1 KJ · m–2 (P content = 0.5%).

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45

Acebo, Cristina, Xavier Fernàndez-Francos, Xavier Ramis e Àngels Serra. "Thiol-yne/thiol-epoxy hybrid crosslinked materials based on propargyl modified hyperbranched poly(ethyleneimine) and diglycidylether of bisphenol A resins". RSC Advances 6, n. 66 (2016): 61576–84. http://dx.doi.org/10.1039/c6ra13158a.

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46

Xu, Xiwei, Songqi Ma, Jiahui Wu, Jintao Yang, Binbo Wang, Sheng Wang, Qiong Li, Jie Feng, Shusen You e Jin Zhu. "High-performance, command-degradable, antibacterial Schiff base epoxy thermosets: synthesis and properties". Journal of Materials Chemistry A 7, n. 25 (2019): 15420–31. http://dx.doi.org/10.1039/c9ta05293c.

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Abstract (sommario):

Epoxy thermosets containing a two-benzene-ring-conjugated Schiff base structure combined excellent controlled degradability, stability, antibacterial properties, and thermal and mechanical properties.

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47

De, Bibekananda, e Niranjan Karak. "Ultralow dielectric, high performing hyperbranched epoxy thermosets: synthesis, characterization and property evaluation". RSC Advances 5, n. 44 (2015): 35080–88. http://dx.doi.org/10.1039/c5ra04248h.

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48

Haybat, Mehmet, Thomas Guenther, Romit Kulkarni, Serhat Sahakalkan, Tobias Grözinger, Thilo Rothermel, Sascha Weser e André Zimmermann. "Characterization of Hermetically Sealed Metallic Feedthroughs through Injection-Molded Epoxy-Molding Compounds". Applied Mechanics 2, n. 4 (30 novembre 2021): 976–95. http://dx.doi.org/10.3390/applmech2040057.

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Abstract (sommario):

Electronic devices and their associated sensors are exposed to increasing mechanical, thermal and chemical stress in modern applications. In many areas of application, the electronics are completely encapsulated with thermosets in a single process step using injection molding technology, especially with epoxy molding compounds (EMC). The implementation of the connection of complete systems for electrical access through a thermoset encapsulation is of particular importance. In practice, metal pin contacts are used for this purpose, which are encapsulated together with the complete system in a single injection molding process step. However, this procedure contains challenges because the interface between the metallic pins and the plastic represents a weak point for reliability. In order to investigate the reliability of the interface, in this study, metallic pin contacts made of copper-nickel-tin alloy (CuNiSn) and bronze (CuSn6) are encapsulated with standard EMC materials. The metal surfaces made of CuNiSn are further coated with silver (Ag) and tin (Sn). An injection molding tool to produce test specimens is designed and manufactured according to the design rules of EMC processing. The reliability of the metal-plastic interfaces are investigated by means of shear and leak tests. The results of the investigations show that the reliability of the metal-plastic joints can be increased by using different material combinations.

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49

Kuang, Xiao, Qian Shi, Yunying Zhou, Zeang Zhao, Tiejun Wang e H. Jerry Qi. "Dissolution of epoxy thermosets via mild alcoholysis: the mechanism and kinetics study". RSC Advances 8, n. 3 (2018): 1493–502. http://dx.doi.org/10.1039/c7ra12787a.

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50

Dragašius, Egidijus, e Inga Skiedraite. "Cure Monitoring of Thermosets Using Disc Bimorph Transducers". Solid State Phenomena 220-221 (gennaio 2015): 380–84. http://dx.doi.org/10.4028/www.scientific.net/ssp.220-221.380.

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Abstract (sommario):

The article discusses the results of experiments on the further development of the method for monitoring the state of the small samples of resin and polymers during curing. The applied method is based on a change in the structure of oscillating transducers leading to variations in the form and/or mode of oscillation. The thin layer of epoxy resin was placed between two piezoelectric transducers in the form of piezoceramic plates. Curing epoxy resin forms a bimorph and its characteristics change along with variations in viscosity or, after the gel point, stiffness. It is possible to establish the level of epoxy resin curing by monitoring changes in the resonance parameters of bimorph elements. The main purpose of cure monitoring of small samples is to develop a new method for evaluating the parameters of resin both before and after the gel point thus taking into consideration that the use of rheological data measured with reference to small samples will be applied for designing or interpreting bulk-flow processes where epoxy may be considered a continuum.

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