| Vibration often causes undesirable consequences, such as unpleasant motions,noise, and dynamic stresses that lead to fatigue and failure of structures, decreasedreliability and poor performance. Polymers have been widely applied for achievingacoustic and vibration damping due to their unique combination of low modulus andinherent damping.Ethylene vinyl-acetate copolymers (EVM700) and polylactic acid (PLA) haveabundant ester groups, and can be used as damping materials due to their high tanδvalues. Furthermore, their Tg are some70℃apart and blending of EVM and PLAshould enable a large effective damping temperature range (EDTR). In this paper, aHaake torque rheometer was chosen to blend EVM with PLA, with dicumyl peroxide(DCP) as the curing agent and triallyl isocyanurate (TAIC) as the curing coagent. Theeffects of compatibilizers and inorganic fillers on the mechanical and dampingproperties were examined in order to prepare new and better performance dampingmaterials with wider EDTR. Then with ethylene vinyl-acetate copolymer (EVM700)and Polylactic acid (PLA) blends as the matrix, dicumyl peroxide(DCP) as the curingagent and azodicarbonamide(AC) as the foaming agent, the EVM/PLA foamedmaterials were prepared by molding. Effects of different blending ratio of EVM/PLA,different content of AC, DCP, silica and different foaming time on the foamingproperties and damping properties of EVM/PLAfoamed materials were examined.Firstly, effects of different compatibilizers including DCP/TAIC, chlorinatedpolyethylene (CPE) and butadiene-acrylonitrile-glycidyl methacrylate terpolymer(NBR-GMA) on the damping properties of materials were studied, results showed that: While DCP content was1.5phr or TAIC content was1.5phr, the compatibility ofEVM/PLA materials was better. But the damping properties decrease with theincreasing of DCP and TAIC. Considering their mechanical properties and dampingproperties, the materials exhibited a good comprehensive performance with1.0phrDCP and0.5phr TAIC. On the research of CPE and NBR/GMA, we got that thecompatibility of materials were better while CPE content was10phr or NBR-GMAcontent was10phr. But the damping properties were not getting better with theimprovement of the compatibility, instead, the damping properties and mechanicalproperties got worse with the addition of CPE and NBR-GMA. Overall, the three kindsof compatibilizer we chosen were bad for the damping properties of materials.Then, effects of inorganic fillers including silica, mesoporous silica, glass beads,mica, silicate and graphene oxide on the damping properties of materials were studied,results showed that: The comprehensive properties of EVM/PLA were better whensilica content was30phr or40phr; The combination of mesoporous silica and silica, orglass beads and silica can improve the damping properties of materials, in addition, thedispersibility of fillers were improved. The system of mica/silica, silicate/silica andgraphene oxide/silica reduced the damping properties of materials.Finally, effects of blending ratio of EVM/PLA, different content of AC, DCP,silica and different foaming time on the damping properties of EVM/PLA foamedmaterials were examined. Results showed that the cell size and foaming capacityincrease with the increasing of PLA; With the increasing of AC, the cell size slightlydecrease and the damping properties have no obvious change, but we still can get thatthe damping properties are the optimum when the AC content is4phr; With theincreasing of DCP, the cell size of materials decline slightly and the dampingproperties change a bit. In addition, the damping properties are the optimum when theDCP content is5phr; With the increasing of foaming time, the cell size of materialsdecline clearly and the damping properties increase significantly. Moreover, both of thecell size and the damping properties have a sudden change in5min; The cell sizedecrease and the cell wall get thicker with the increasing of silica, and the dampingproperties are overall improved. |
PDF Full Text Request