Study On Electric And Dynamic Viscoelastic Properties Of Carbon Black Filled Multi-component Polymers Composites

The properties of conductive polymeric composites are related not only to the components and structure but also to the distribution of conductive fillers in polymeric matrix. In this thesis, the conductive and the dynamic viscoelastic properties of carbon black (CB)/ nylonl212 (PA1212)/ polypropylene(PP) composites were primarily investigated compared with CB/PP and CB/PA1212 composites in order to explore the conductive mechanism of CB filled multi-component polymers composites and establish the connection of electrical properties with dynamic viscoelastic properties.The selective distribution of CB in multi-component polymers (PA1212/PP) is observed by transmission electron microscopy (TEM). It is found that most of the CB particles are located in PA1212 phase, but nearly not in PP phase. High CB concentration in some parties of composites is resulted from selective location of CB, and leading to form conductive network due to agglomeration of CB particles Hence, low CB weight content can also endow composite composed of PA1212 and PP with eximious electric conductivity.Studies on the characteristic of R^T for CB/PA1212/PP composites were carried out through an examination of the temperature(T) dependence of the resistance(ρ). The results reveal that multi-component polymers matrixes tend to weaken negative temperature coefficient(NTC) effect. Because of the selective location of CB in PA1212 phase, the characteristic of R T for CB/PA1212/PP composites are similar to CB/PA1212 composites.The dynamic viscoelastic properties of CB filled polymeric composites were investigated by examining the CB concentration ( φ_CB) dependence of the dynamic viscoelastic functions. The results reveal that in the low-frequency (ω) region, dynamic viscoelastic functions such as dynamic storage modulus (G') and dynamic loss modulus (G") could sensitively reflect the change of Φ_CB There existed a percolation of dynamic viscoelastic function (φ_p2), and the φ_p2 isclose to the electric percolation t>pi). Substituting parameter A for A, a modifiedKerner-Nielsen equation is obtained and used to analyze the formation of CB network structure. It is suggested that the parameter A is associated with CB agglomeration. With increase of CB concentration, the remarkable change of parameter A reflectes the development and formation of CB network. The viscoelastic percolation for CB/PP and CB/PA1212 composites could be verified on the basis of the modified equation, and the parameter A under different CB concentration corresponds to its specific/). However the equation could hardly be applied into CB/PA1212/PP system. Interference of the dispersed phase (PP) made the dynamic viscoelastic properties of CB/PA1212/PP more complex.