不同粒径纳米二氧化硅对三元乙丙橡胶性能影响的分子动力学模拟

Molecular Dynamics Simulation of Effect of Nano-SiO_(2)with Different Particle Sizes on Properties of EPDM

运用Materials Studio 9.0软件构建三元乙丙橡胶(EPDM)模型和纳米二氧化硅(SiO_(2))粒径分别为1.2,1.5,1.8和2.0 nm的纳米SiO_(2)/EPDM复合材料模型,分析纳米SiO_(2)对纳米SiO_(2)/EPDM复合材料在高压低温(100 MPa/230 K)条件下的微观结构及力学性能的影响。结果表明:与EPDM相比,填充不同粒径纳米SiO_(2)的复合材料的玻璃化温度(Tg)都有不同程度升高,其中纳米SiO_(2)粒径为1.2 nm的复合材料的Tg比EPDM高5 K;复合材料的微观结构发生改变,均方位移和自由体积分数都有所减小,减幅随纳米SiO_(2)粒径的减小而增大,内聚能密度均有所增大,增幅随纳米SiO_(2)粒径的减小而增大,但纳米SiO_(2)粒径对复合材料的全原子径向分布函数影响不大;复合材料的力学性能提高,提高幅度随纳米SiO_(2)粒径的增大而减小,纳米SiO_(2)粒径为1.2 nm时,复合材料的体积模量增大5.98%,剪切模量增大198.00%,弹性模量增大34.65%。

The model of ethylene propylene diene rubber(EPDM)and the models of nano-silica(SiO_(2))/EPDM composites with nano-SiO_(2)particle sizes of 1.2,1.5,1.8 and 2.0 nm were constructed by using Materials Studio 9.0 software,and the effects of nano-SiO_(2)on the microstructures and mechanical properties of nano-SiO_(2)/EPDM composites under high pressure and low temperature(100 MPa/230 or 240 K)conditions.The results showed that compared with that of EPDM,the glass transition temperature(Tg)of the composites filled with nano-SiO_(2)of different particle sizes increased to varying degrees,and the Tg of the composite with nano-SiO_(2)particle sizes of 1.2 nm was 5 K higher than that of EPDM.The microstructures of the composites were changed,the mean square displacements and fractional free volumes decreased,and the decrease amplitudes increased with the decrease of nano-SiO_(2)particle sizes.The cohesive energy densities were improved,and the increase amplitudes increased with the decrease of nano-SiO_(2)particle sizes.But nano-SiO_(2)particle sizes had little effect on the all-atom radial distribution functions of the composites.The mechanical properties of the composites were improved,and the improvement amplitudes decreased with the increase of nano-SiO_(2)particle sizes.When nano-SiO_(2)particle size was 1.2 nm,the bulk modulus of the composite increased by 5.98%,the shear modulus increased by 198.00%,and the elastic modulus increased by 34.65%.