炭黑填充聚苯乙烯熔体流变行为

研究了炭黑(CB)填充聚苯乙烯(PS)熔体的稳态和动态流变行为. CB/PS复合体系在CB体积分数φ=0.06时发生逾渗转变. 结果表明, 低应变区熔体模量降低主要归因于粒子-粒子及粒子-高分子间作用力的破坏, 高应变下模量的急剧下降则主要与高分子链间解缠结有关. 采用“两相”模型拟合线性动态流变行为, 发现应变放大因子A_f(φ)、填充相模量及松弛指数与温度有关. A_f(φ)~φ关系符合Guth方程和扩散控制的粒子簇聚集模型. “粒子相”形状参数与聚集体分维度均随温度升高而有所降低, 说明CB粒子聚集体因团聚而趋于各向同性, 应变放大效应减弱. “粒子相”特征模量G'_f1(φ)和G"_f0(φ)与φ关系满足标度律. 当φ > 0.06时, G'_f1(φ)和G"_f0(φ)及其标度指数均随温度升高而明显降低, 其G'_f1(φ)变化幅度略大于G"_f0(φ), 说明“粒子相”弹性与黏性组分具有不同的温度依赖性. 随着温度升高, 扩散控制的CB粒子团聚过程加快, 应变放大效应减弱.

Rheological Behavior of Carbon Black Filled Polystyrene Melts

Steady and dynamic rheological behavior of carbon black(CB) filled polystyrene(PS) composites were investigated. The CB/PS composites exhibit percolation transition at critical CB volume fraction(φ) of 0.06. The nonlinear rheology from dynamic strain sweep was related to the breakdown of particle-particle and particle-polymer interactions at small strains and the disentanglements of macromolecular chains at large strains. Analyzing the linear dynamic rheology of the composites according to the two-phase model revealed that the strain amplification factor A_f(φ), characteristic moduli and relaxation factor of the filler phase varied as a function of temperature. Dependence of A_f(φ) on φ followed the Guth equation and the diffusion-controlled cluster-cluster aggregation model. The shape factor and fractal dimension of the "filler phase" decreased with increasing temperature, suggesting that, as temperature was increased, the diffusion-controlled CB particle aggregation process was accelerated and the strain amplification effect was weakened. The elastic and viscostic characteristic modulus components of the "filler phase" exhibited scaling dependences on φ. At φ>0.06, both characteristic moduli of the "filler phase" and their scaling exponents demonstrated decrease tendencies with increasing temperature and the variation of the elastic component was slightly higher than the viscostic component revealing different temperature dependences of the elastic and viscostic characteristic modulus components of the "filler phase".