等规聚丙烯/炭黑等温结晶过程中流变与导电行为的关联与同步测试

采用流变-导电行为同步测试方法,研究了等规聚丙烯(iPP)/炭黑(CB)复合体系的等温结晶行为,发现当CB体积含量φCB远高于渗流转变上限时,其体系的流变行为与导电性能均在某一特征时间处发生突变,电阻突变的特征时间短于动态储能模量(G′)或法向应力(FN)突变的特征时间,表明结晶诱导期存在CB粒子运动,促使CB粒子在晶粒尺寸增长期形成渗流网络;另一方面,与静态方法相比较,动态方法所测特征时间较短,表明动态方法对体系结晶结构变化的响应较静态方法更为灵敏.

STUDY ON CORRELATION BETWEEN RHEOLOGICAL AND CONDUCTIVEBEHAVIOR THROUGH SIMULTANEOUS MEASUREMENTS DURINGISOTHERMAL CRYSTALLIZATION FOR CARBON BLACKFILLED ISOTACTIC POLYPROPYLENE

The kinetics of isothermal crystallization for isotactic polypropylene(iPP) containing different volume fraction(φ_(CB)) of carbon black(CB) was evaluated by using differential scanning calorimetry(DSC) at 137.5℃,139.5℃ and 141.5℃ with moderate rates of crystallization.Simultaneous measurements of rheological and conduction behaviors were performed to probe the process of isothermal crystallization in dynamic and static modes.It was found that when CB volume fraction φ_(CB) was 0.09,the characteristic time for sharp resistance variation was comparable to those for shape changes in storage modulus(G′) or normal force(F_N).At φ_(CB) of 0.13 and 0.17 above the upper limit of percolation transition,however,the characteristic time resulted from resistance was much less than those from G′ or F_N,which could be explained by the formation of the percolation network during the induction period of crystallization.On the other hand,for all φ_(CB) and crystallization temperatures,the characteristic time from dynamical method was less than that from the static one,which indicated that the dynamical method was more sensitive to the structural transformation than the static one.It was suggested that rheological and electrical simultaneous measurements endowed us a novel approach to probe the formation of percolation network involving in crystallization of polymer matrix.