【摘要】 采用PVT膨胀仪测试了添加不同防老剂的天然橡胶(NR)复合材料的压力-体积-温度(P-V-T)属性,通过最小二乘法拟合得到Tait方程参数,预测了体系的热膨胀系数(α)和等温压缩系数(β),结果表明,Tait状态方程可用来预测该复合材料体系的P-V-T行为,NR复合材料的α值随着压力的增大而减小,随温度变化不明显;β值随压力的增大而减小,且随着温度的升高而升高.分子模拟结果观察了体系凝聚态结构在不同温度下的变化,表明其变化原因是升温使体系自由体积增大,分子链的活动性增强,同时观察到单独加入防老剂4010NA或防老剂RD的体系α和β的值较大,说明其尺寸稳定性差,而当同时加入4010NA和RD进行防老剂并用时,体系的α和β值均较小,表明此复合材料体系不容易产生变形;通过分子动力学模拟手段计算了NR复合材料的内聚能密度(CED)随温度的变化规律,对于2种防老剂并用的体系,其CED比较大,说明分子间相互作用力较强,从而体系尺寸稳定性好,受温度和压力的影响小.更多还原

【Abstract】 The pressure-volume-temperature( P-V-T) properties of natural rubber( NR) composites with different antioxidants were studied. The parameters of Tait equation was calculated and compared with experiments. The results showed that the P-V-T relationship calculated by Tait equation agreed well with the observation results,the residual means between theoretical calculation and experimental values were all less than 0. 01 which indicated that the Tait equation can be used to describe the P-V-T relationship of the natural rubber composites. Thermal expansion coefficients( α) and isothermal compressibility( β) of nature rubber were evaluated by Tait equations. It’s showed that α decreases with the increase of pressure,but nearly doesn’t change with temperature increasing. β will decrease when pressure becomes high and increases with the increase of temperature. This is well explained by molecular simulation that high temperature or low pressure will lead to an expansion on free volume of the system,so that the activity of the molecular chain is enhanced.When there is only one kind of antioxidant in the composites,the values of both α and β are large,but when these antioxidants are used together,the values of both α and β are small,and the composite has the best size stability. Furthermore,the cohesive energy density( CED) obtained from molecular simulation shows that the intermolecular interaction force of nature rubber with two kinds of antioxidants is high,so it is hard for α or βto change. Through accurate description of the changes of α and β with different pressures and temperatures for the composites,a method with the function of guiding processing and application research was attempted.更多还原