Structure And Properties Of Functional EVA/SBR TPV And EVA/EVM TPV

Thermoplastic vulcanizate(TPV) based on ethylene-vinyl acetate copolymer(EVA)/styrene butadiene rubber(SBR) blends were prepared by dynamic vulcanization. The mechnical properties, morphology, morphology evolution of the rubber phase and dynamic viscoelastic behavior such as Mullins effect with its reversibility of TPV and compression set with its reversibility, were researched systematically. The influences of the weght ratio of rubber and plastic, the reinforcing agents in rubber phase on the properties of TPV were investigated. The EVA/SBR TPV was used as raw material and metallographic sandpaper was used as template to prepare the rough surfaces with micronstructure, moreover, the contact angle was increased remarkablely. The EVA/CB/styrene-ethylene-butene-styrene block copolymer(SEBS) blends were prepared by melting compounded and its PTC effect was investigated. TPV based on EVA/ethylene-vinyl acetate copolymer rubber(EVM) was prepared by dynamic vulcanization and the mechnical properties, morphology and Mullins effect under tensile mode were researched. The water-swellable EVA/EVM/crosslinked sodinm polpacrylate(CPNa AA) TPV was prepared by incorporation with CPNa AA in the EVM phase. The mechnical properties and water swellable behavior of EVA/EVM/CPNa AA were investigated. The main results were shown as below:(1) The EVA/SBR TPVs with different weight ratios were prepared by dynamic vulcanization. Considering the proper mechanical properties, the weight ratio of EVA/SBR TPVs should range from 30/70 to 40/60. The EVA/SBR TPVs with different vulcanization time were prepared by dynamic vulcanization and the SBR phase morphology evolution was researched by field emission scanning electron microscope(SEM). Experimental results indicated that the rubber phase was fragmented continuously during the dynamic vulcanization and was evolved into spherical-like particles with the diameters of 3~6 μm at 8 min. The size of the dispersed phase was decreased with increasing of dynamic vulcanization time and leading to the improvement of the mechnical properties.(2) The EVA/SBR TPV was reinforced by incorporation with CB in SBR phase. The experimental results indicated that the tensile strength, tearing strength and shore A hardness were increased with increasing CB content while the elongation at break and tensile set at break were decreased. When the CB incorporation was 40 phr, the tensile strength was achieved the maximum value. The EVA/polyolefin elastomer(POE)/SBR TPV was prepared by replacement partialy EVA matrix with POE. Considering the proper mechanical properties, the weight ratio of EVA/POE/SBR TPV should be 25/5/70, and the prepared TPV had low shore A hardness and large elongation at break. The EVA/POE/SBR TPV was reinforced by incorporation with CB in SBR phase. The experimental results indicated that the tensile strength, tearing strength and shore A hardness were increased with increasing of CB content while the elongation at break and tensile set at break were decreased. When the CB incorporation was 40 phr, the tensile strength was achieved the maximum value, indicating that the CB could enhance TPV remarkablely.(3) The Mullins effect under tensile and compression mode were researched respectively. Mullins effect results showed that the maximum value of stress and internal friction loss appeared at first tensile(compression) at specific strain and both the maximum stress and internal fricion loss deceased obviously at second tensile(compression) while only decreased slightly at the subsequent tensile(compression) cycle. The residual deformation decreased with the increasing of number of loading-unloading cycles. Increasing the tensile(compression) strain, the maximum stress, internal friction loss and residual deformation increased obviously. Compared with that of EVA/SBR TPV, the EVA/POE/SBR TPV had relatively lower internal fricion loss, indicating the higher elasticity of EVA/POE/SBR TPV. However, the EVA/SBR/CB TPV had higher internal fricion loss than that of EVA/SBR TPV. The SBR vulcanizate was reinforced by CB; moreover, the amplification effect of Mullins effect of the series CB reinforced SBR vulcanizates were investigated systematically. Mullins effect could be significantly enhanced with the increasing CB dosage and compression strain. The reversibility behavior of Mullins effect and its reversibility mechanism were investigated and the results indicated that the maximum stress at specific strain could only partially recover at room temperature and improving heat-treatment temperature could improve the reversible degree of the TPV effectively, the best heat-treatment temperature for the reversibility ability of Mullins effect of EVA/SBR TPV was 80 °C.(4) The compression set and its reversible recovery were researched. The results indicated that both improving ratio of rubber and plastic and improving heat-treatment temperature could improve the reversible recovery of compression set of the TPVs. The mechanism of compression set reversible recovery was also investigated. The generalized Maxwell model was used to describe the process of compression set recovery successfully and the influences of blending ratio and heat-treatment temperature on the relaxation time in each stage of the recovery course and activity energy were discussed quantificationally.(5) The EVA/SBR TPV was used as raw material and metallographic sandpaper was used as template to prepare the rough surface with micronstructure. The results indicated that the contact angle of TPV was increased remarkablely after mould pressing with metallographic sandpaper.(6) The EVA/EVM TPVs with different weight ratios were prepared by dynamic vulcanization and the mechnical prepoties, morphology of EVA/EVM TPV were investigated. Considering the proper mechanical properties, the weight ratio of EVA/EVM TPV should range from 30/70 to 40/60. The water-swellable EVA/EVM/CPNa AA TPV was prepared by incorporation with CPNa AA particles in the EVM phase. The mechnical properties and water swellable behavior of EVA/EVM/CPNa AA were investigated. The results showed that the mechanical properties of the WSRs were decreased obviously with the increase of CPNa AA dosages; however, water-swelling properties of the WSRs were increased significately. The maximum water-swelling ratio of WSRs with 60 phr CPNa AA was 756 % after 288 h immersion with distilled water.(7) The EVA/CB/SEBS blends with different weight ratios were prepared by melting-compounding. The volume expansion behavior of EVA and SEBS were researched respectively and the PTC effect of EVA/CB/SEBS blends was also researched. The results indicated that the resistivity increased with the increase of SEBS content; however, the PTC effect was weakened. The mechanism of PTC behavior was researched based on the volume expansion-temperature curve.