Study On The Properties Of Short Aramid Fiber Reinforced Ethylene Propylene Diene Monomer

Short aramid fiber?AF?reinforced ethylene propylene diene monomer?EPDM?composite that combined the high elasticity of rubber with the high modulus of AF,and given the composite excellent propoties such as high modulus and high tear strength.Rubber products were often subjected to alternating stress?strain?,therefore,the interface of fiber/rubber composite has always been the weakness of fiber/rubber composite.However,the stress was transmitted through the interface layer,so the damage of materials often occurs from the interface.So,improving the fiber/rubber interface has great significance for improving the performance of composite materials.In this paper,the influence of different AF treatment such as thermal oxidation treatment,complexation treatment or coated with epoxy resin,butadiene vinylpyridine rubber latex,silane coupling agent,trihydroxy acrylate?TMPTA?and pentaerythritol triacrylate?PETA?on the performance of composites was studied.The main research contents were as follows:?1?The addition of AF significantly improved the comprehensive performance of CB-EPDM composite,but the comprehensive performance of the composite material gradually decreased when the AF content was too high,the comprehensive performance was optimal when the AF content was 5phr.Thermal oxidation treatment can activate the AF surface and increase its reactivity.Complexation treatment can destroy the AF surface hydrogen bonds,and reduce the surface crystallinity,which increased the surface roughness and activity,but the degree of AF damage increased with the increasing of CaCl₂ concentration.The addition of AF changed the stress-strain curve of composite,namely the greater the slope of the curve that the enhancement effect of AF was more remarkablely.Firstly,AF was subjected to thermal oxidation treatment,and then treated with CaCl₂ complexation treatment,and finally coated with polar VPL,which formed a flexible interface layer on the AF surface.The formation of the flexible interface layer compensated the damage of the complexation treatment to AF,and weakened the filler network structure of the composite,reduced the Payne effect of the composite and increased its elongation at break.The reinforcing effect of the fiber was synchronized with the strain,namely the reinforcing effect was exhibited under strain immediately.The good interfacial bonding facilitate transfered of the stress and hindered the crack propagation,and the complex processing AF can promote the bonding of the AF/rubber interface,expressed as composite material DMA loss factor peak reduction and RDE value increase.?2?Trihydroxy acrylate?TMPTA?and pentaerythritol triacrylate?PETA?coated with AF can improve the tensile stress of AF/CB-EPDM composites,but the tensile strength and elongation at break will decrease,and with the increased of TMPTA and PETA content,the degree of decline was more obviously.Maleic anhydride polybutadiene liquid rubber?MLPB?can improve the dispersion of AF and enhance the comprehension performance of AF/CB-EPDM composites.Chosen the TMPTA or PETA and MLPB combination treated AF,the elongation at break and tensile strength decline situation of the composite didn't changed.The complex treatment made that the stress-strain curve of the composite showed a large slope at the beginning of the strain,but the enhancement effect was weakened after the initial enhancement.The AF reinforced rubber composites exhibited a significantly Mullins effect on fatigue initial stage,that is,rapidly decreased in the initial modulus,and then tended to be gentle.After a certain number of cycles under the condition of strain control,the RDE value of the composite decreased gradually with the increasing of strain,the better interfacial adhesion kept the RDE value at a higher level,and the composite material had a hysteresis effect after the fatigue processing,namely the enhancement effect was weakened at the beginning of the strain.?3?The combination of linear low density polyethylene?LLDPE?and CB-EPDM composite can improve the tensile strength,tear strength and cutting resistance of CB-EPDM composites,but the processing performance of the composite was gradually reduced with the increasing of LLDPE content.The combination of LLDPE and CB-EPDM reduced the maximum torque value of the vulcanization characteristics of CB-EPDM material and prolonged the curing time of CB-EPDM composite.LLDPE had a good compatibility with CB-EPDM composites,and the microscopic topography?SEM?of CB-EPDM/LLDPE composites befor and after fatiguing didn't show phase separation.Furthermore,there was only one loss peak in dynamic mechanical property test?DMA?.LLDPE had a low glass transition temperature,which combined with CB-EPDM can move the glass transition temperature of CB-EPDM composites to a low temperature.In addition,the reinforcement effect of LLDPE on CB-EPDM composites was synchronization with strain before and after fatiguing.?4?Silane coupling agent?Si69,KH550,KH560 and KH570?and epoxy resin?E51?were selected to coat AF and then prepare composites.The change in the properties of AF/CB-EPDM/LLDPE composites was researched.Compared with the composite AF/CB-EPDM/LLDPE,which prepared by untreated AF,AF coated with silane coupling agent and epoxy resin can promote the interface bonding between AF and the substrate at a certain extent.The silane coupling agent can participate in the vulcanization of the matrix to form a covalent bond during the matrix vulcanization process,improving the interface bonding between the AF and the matrix.The epoxy resin was partially cured before coating,while the uncured portion continued to crosslink during subsequent processing.The addition of epoxy resin formed a rigid interface on the surface of the fiber,and the SEM image showed that the destruction of AF was severe and showed severe fibrillation.From the comparison of the performance of each composites material before and after a certain period of fatigue,the composites prepared by AF coated with epoxy resin had the best comprehensive performance retention rate.