The physical and mechanical properties of blends composed of two kinds of epoxy resins of different numbers of functional groups and chemical structure were studied. One of the resins was a bifunctional epoxy resin ba...The physical and mechanical properties of blends composed of two kinds of epoxy resins of different numbers of functional groups and chemical structure were studied. One of the resins was a bifunctional epoxy resin based on diglycidyl ether of bisphenol A and the other resin was a multifunctional epoxy novolac resin. Attempt was made to establish a correlation between the structure and the final properties of cured epoxy samples. The blend samples containing high fraction of multifunctional epoxy resin showed higher solvent resistance and lower flexural modulus compared with the blends containing high fraction of bifunctional epoxy resin. The epoxy blends showed significantly higher ductility under bending test than the neat epoxy samples. The compressive modulus and strength increased with increasing of multifunctional epoxy in the samples, probably due to enhanced cross-link density and molecular weight. Morphological analysis revealed the presence of inhomogeneous sub-micrometer structures in all samples. The epoxy blends exhibited significantly higher fracture toughness（by 23% at most） compared with the neat samples. The improvement of the fracture toughness was attributed to the stick-slip mechanism for crack growth and activation of shear yielding and plastic deformation around the crack growth trajectories for samples with higher content of bifunctional epoxy resin as evidenced by fractography study.展开更多
Epoxidation of the carbon-carbon double bonds on unsaturated rubber macromolecules can produce novel modified rubber species with special properties,and construct eco-friendly crosslinking pathway via the reaction of ...Epoxidation of the carbon-carbon double bonds on unsaturated rubber macromolecules can produce novel modified rubber species with special properties,and construct eco-friendly crosslinking pathway via the reaction of epoxide groups to solve the problems brought by conventional sulfur vulcanization system.In this contribution,a novel modified product of isobutylene isoprene rubber(IIR),epoxyfunctionalized IIR(EIIR)was successfully prepared by in situ epoxidation technique for the first time,and the crosslinking of EIIR was achieved by the reaction of oxirane groups with maleic anhydride(MAH)without additional additives.The reaction conditions for preparing EIIR were optimized through systematic research on the epoxidation process.Under optimal condition,the degree of epoxidation of the rubber reached around 99%without side reactions.The obtained EIIR/carbon black composites cured by MAH had excellent mechanical properties comparable to those of IIR composites.More importantly,compared with IIR composites,the air-tightness of the EIIR composites was improved by about 50%,and the flexural fatigue life of first-level cracks and sixth-level cracks was increased by several times.The significant improvement of these properties is of great significance for the application safety and energy saving of IIR materials.展开更多
文摘The physical and mechanical properties of blends composed of two kinds of epoxy resins of different numbers of functional groups and chemical structure were studied. One of the resins was a bifunctional epoxy resin based on diglycidyl ether of bisphenol A and the other resin was a multifunctional epoxy novolac resin. Attempt was made to establish a correlation between the structure and the final properties of cured epoxy samples. The blend samples containing high fraction of multifunctional epoxy resin showed higher solvent resistance and lower flexural modulus compared with the blends containing high fraction of bifunctional epoxy resin. The epoxy blends showed significantly higher ductility under bending test than the neat epoxy samples. The compressive modulus and strength increased with increasing of multifunctional epoxy in the samples, probably due to enhanced cross-link density and molecular weight. Morphological analysis revealed the presence of inhomogeneous sub-micrometer structures in all samples. The epoxy blends exhibited significantly higher fracture toughness（by 23% at most） compared with the neat samples. The improvement of the fracture toughness was attributed to the stick-slip mechanism for crack growth and activation of shear yielding and plastic deformation around the crack growth trajectories for samples with higher content of bifunctional epoxy resin as evidenced by fractography study.
基金the National Key Research and Development Program of Chinathe National Natural Science Foundation of China(Nos.2022YFB3704800,2022YFB3704802 and 52273051)the Fundamental Research Funds for the Central Universities(No.JD2221)。
文摘Epoxidation of the carbon-carbon double bonds on unsaturated rubber macromolecules can produce novel modified rubber species with special properties,and construct eco-friendly crosslinking pathway via the reaction of epoxide groups to solve the problems brought by conventional sulfur vulcanization system.In this contribution,a novel modified product of isobutylene isoprene rubber(IIR),epoxyfunctionalized IIR(EIIR)was successfully prepared by in situ epoxidation technique for the first time,and the crosslinking of EIIR was achieved by the reaction of oxirane groups with maleic anhydride(MAH)without additional additives.The reaction conditions for preparing EIIR were optimized through systematic research on the epoxidation process.Under optimal condition,the degree of epoxidation of the rubber reached around 99%without side reactions.The obtained EIIR/carbon black composites cured by MAH had excellent mechanical properties comparable to those of IIR composites.More importantly,compared with IIR composites,the air-tightness of the EIIR composites was improved by about 50%,and the flexural fatigue life of first-level cracks and sixth-level cracks was increased by several times.The significant improvement of these properties is of great significance for the application safety and energy saving of IIR materials.
