不同温度和压强下甲基乙烯基硅橡胶聚合物的分子动力学模拟研究

Molecular Dynamics Simulation of Methyl Vinyl Silicone Rubber Polymer at Different Temperatures and Pressures

分子模拟技术因能够解释聚合物材料宏观结构和微观结构的关系,故被广泛应用于聚合物材料的性能研究。材料的微观物理性质用密度来表征,材料的微观力学性质用杨氏模量和泊松比来表征。在模拟体系中,用Materials studio 7.0软件构建一条原子数为237的分子链,经几何及能量优化得到稳定结构,晶胞参数设置为30×30×30,然后使用Amorphous Cell构建3种不同温度体系分子链数为9的晶胞,密度设置为0.98 g/cm3,最后用Forcite Plus模块在不同压强下模拟得到9中不同形态结构及力学性能参数,分析MVQ分子受温度和压强的变化规律。结果表明,当温度升高时,整个分子链的运动能力大幅度增加。在同一温度不同压强的模拟体系中,分子链运动的能力随着压强的增大而逐渐减小。298 K时,压强从1 MPa增加到10 MPa时,体积模量减小了30.6%,增加到0.01 GPa时,体积模量减小了65.6%。同样,剪切模量和杨氏模量分别在升至10 MPa和0.01 GPa减少了64.3%、88.5%和60.8%、86.9%。500 K时,此时MVQ呈橡胶态,分子的弹性模量发生质变,弹性模量迅速增大,压强升至0.01 GPa,又迅速减小。

Molecular simulation technology is widely used to study the properties of polymer materials for which can explain the relationship between macro structure and micro structure of polymer materials. The micro physical properties of materials are characterized by density,and the micro mechanical properties are characterized by Young’s modulus and Poisson’ s ratio. In the simulation system,a molecular chain with 237 atoms is constructed using materials studio 7. 0 software. After geometric optimization and energy optimization,the lowest stable structure obtained and the cell parameters were set as 30 × 30 ×30. Then,Amorphous cell was used to construct three different temperature systems with molecular chain number of 9,and the density was set as 0. 98 g/cm3,Finally,the Forcite plus module was adopted to simulate of MVQ under different pressures. Nine different morphological structures and mechanical properties parameters were obtained under different pressures. The results show that,when the temperature increases,the mobility of the whole molecular chain increases greatly. At the same temperature and different pressure simulation system,with the increase of pressure the ability of molecular chain movement decreases. When the pressure increases from 1 MPa to 10 MPa at 298 K,the bulk modulus decreases by 30. 6%,the pressure increases to 0. 01 GPa,decreases by 65. 6%. Similarly,when the shear modulus and Young’s modulus increased to 10 MPa and 0. 01 GPa,the shear modulus and Young’s modulus decreased by 64. 3%,88. 5% and 60. 8%,86. 9%. At 500 K,so the MVQ is in rubber state,the elastic modulus of MVQ molecule changes qualitatively. The elastic modulus increases rapidly,and the pressure rises to 0. 01 GPa,and then decreases rapidly.