Preparation,Microstructure And Structure-properties Investigation Of Heat And Oil-resistant TPVs Based On EVM/PVDF

Thermoplastic Vulcanizates(TPVs)are prepared by a dynamic vulcanization(DV)process,a high-content(50 to 80 wt.%)of rubber phase as dispersed phase throughout the continuous thermoplastic matrix is required to achieve good elasticity and good processability of TPVs.TPVs,which have the advantages of short processing process(no vulcanization process),low energy consumption and high production efficiency features,have been considered as a typical "green" polymers due to they combine the excellent elasticity of conventional vulcanized rubbers and the good processing performance and recyclability of thermoplastics.With the continuous expansion of TPVs applications,traditional TPVs,such as EPDM/PP TPVs,have been difficult to meet in the field of oil resistance and other requirements,as heat and oil-resistant TPVs have unique advantages in automotive,oil pipeline,oil seals and other fields,so the development of oil-resistant,especially heat and oil-resistant TPVs have attracted considerable attention in recent years.For all material properties are closely related to the microstructure.Therefore,the microstructure and phase inversion mechanism of TPVs must be clearly understood for the preparation of high performance TPVs.In addition,the microstructure and properties of TPVs are affected by a variety of factors,a clear understanding of how the various factors affect the microstructure and properties of TPVs contribute to prepare TPVs with fine microstructure,excellent performance.In this paper,we aim to prepare a novel TPVs with fine microstructure and excellent heat and oil-resistant properties based on ethylene-vinyl acetate rubber(EVM)and poly(vinylidene fluoride)(PVDF).The microstructure and phase inversion mechanism and structure-property relationship of EVM/PVDF TP Vs during dynamic vulcanization were investigated by sampling during dynamic vulcanization process.In addition,we also studied the influence of rubber/rubber ratio,the degree of crosslinking of rubber phase and the rotor speed of Haake mixer on the microstructure and properties of EVM/PVDF TP Vs in order to produce TP Vs with better performance.The investigation results are as follows:(1)The EVM/PVDF TP Vs were prepared successfully and dispersed in the PVDF plastic matrix at a size of 20-100 nm,and the EVM rubber nanoparticles were aggregated to form a fibrous structure.At the initial stage of dynamic vulcanization,the EVM rubber phase and the PVDF plastic phase formed a continuous phase structure;with the DV process,the EVM merged and still showed a continuous phase structure;with the increase of the crosslinking degree of EVM phase,EVM nanometer droplets no longer merged and form nanoparticles,and phase phase inversion occurs,forming a unique fibrous structure.(2)With the DV process,the network structure formed by EVM rubber nanoparticles weakened,rheological properties improved,rheological extrusion after the apparent smooth,elastic performance slightly worse,but still maintain a good elasticity,mechanical properties become better,heat and oil-resistant performance slightly improved.EVM/PVDF TP Vs have good recyclability,and the mechanical properties of the EVM/PVDF TP Vs have not decreased significantly after repeated processing.(3)EVM/PVDF TP Vs prepared by different rubber/plasticr ratio,crosslinking degree and rotor speed all found a large amount of rubber nanoparticles(aggregates)dispersed in PVDF matrix;rubber and plastic ratio,the degree of crosslinking has a significant impact on performance,when the rotor speed increased to 80 rpm no obvious change on the performance with the rotor speed increase.