| In this paper,EVM-GMA vulcanizate was first prepared with ethylene-vinyl acetate-glycidyl methacrylate rubber(EVM-GMA)as the matrix and methyltetrahydrophthalic anhydride(MTHPA)as a new type of crosslinking agent.The effects of the amount of cross-linker on the basic properties and hot-air aging properties of the materials were studied and compared with the samples cured by traditional peroxide vulcanization systems.Based on this,the cross-linking mechanism of EVM-GMA reacting with MTHPA was proposed and a "model vulcanization reaction" was designed to prove its rationality.Then,the binary blends with shape memory properties were prepared by using EVM-GMA and polyvinyl chloride(PVC)as the matrix.The effects of different blending ratios and different driving temperatures on the shape memory properties and basic properties of the materials were studied.Finally,EVM-GMA/PLA thermoplastic vulcanizates were prepared by dynamic vulcanization technology using EVM-GMA and polylactic acid(PLA)as matrix and the effects of the different amount of cross-linker on the phase morphology,phase transition,crystallization properties,rheological behavior and(dynamic)mechanical properties were studied.The results indicated that an optimum of curing,mechanical properties and aging resistance were found at a molar ratio of MTHPA to GMA of 1:2.The new curing reaction was faster compared to the traditional peroxide vulcanization system and the mechanical properties,compression set and hot-air aging performance were superior as well,which can be regarded as a more excellent vulcanization system.Besides,the "model vulcanization reaction" indicated that one molecule of MTHPA can "bridge" two epoxy side groups on the adjacent molecular chain of EVM-GMA to realize rubber cross-linking,which proved that the cross-linking mechanism based on epoxy-anhydride reaction proposed in this paper was reasonable.In the EVM-GMA/PVC blend system,the EVM-GMA phase and the PVC phase showed a typical "sea-island" structure,in which PVC dispersed as an "island" phase in the EVM-GMA "sea" phase.The two-phase interface was fuzzy and had certain compatibility,and the mechanical properties of the blends changed from soft and tough to hard and strong as the proportion of PVC increased,which exhibited excellent physical and mechanical properties.Besides,EVM-GMA/PVC blends with different proportions all exhibited excellent dual shape memory properties,among which the shape recovery ratio of E90P10 sample was the highest.It was beneficial for the material to obtain a higher shape recovery ratio when the driving temperature was increased.Triple shape memory test showed that the E70P30 sample had excellent triple shape memory performance,and its total recovery ratio was as high as 90.46%.In the EVM-GMA/PLA dynamic vulcanization system,TPVs exhibited low viscosity similar to that of non-dynamic vulcanized samples in the high frequency region.After dynamic vulcanization to form a three-dimensional network,the samples still have excellent processing properties,and the addition of DCP made the material have high tensile strength,elongation at break and low permanent breaking deformation ratio,therefore,the material showed excellent physical and mechanical properties.The simple physical blended EVM-GMA/PLA sample showed a typical "sea-island" structure,where PLA dispersed as the "island" phase in the EVM-GMA "sea" phase,but the addition of DCP caused a phase transition in the material,which changed it from a "sea-island" structure to a bicontinuous structure.In addition,DCP can promote the crystallization of TPVs,and the greater the amount of DCP,the higher the crystallinity. |
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