A Study On The Morphology, Rheology And Conductivity Of Carbon Black-Filled Immiscible Polymer Blends

Many researches have focused on conductive polymer composites, especially carbon black (CB)-filled polymer composites. However, the relationships between microstructure and macro-properties are not well established, such as dispersion state or content of CB, dispersion content of CB in polymer component, formation of CB conductive network. The objectives of the work focused on the dispersion state of CB, and establish the relationship of morphology, rheology, and conductivity.At first, the factors to control the dispersion state of particles are studied and compared, according to the dynamic and thermodynamic factors. In this work, the morphology and electrical properties of Linear Low Density Polyethylene (LLDPE)/ Ethylene-Methyl Arylate copolymer (EMA) blends filled with CB are investigated. CB are found to locate mainly in the LLDPE phase, but a little of CB remain staying in EMA phase when the CB loading increase. The factors of viscosity ratio (dynamic factors) are stronger than the interaction of CB to polymer phase (thermodynamic factors). And the conductivity and PTC intensity of LLDPE/ EMA/CB composites change with the morphology and crystallite melting processing of rich CB-in phase.Secondly, as mentioning before, there exists distribution ratio of CB between LLDPE and EMA phase, and no clear description is given in any research works. It is found that the rheological method is sensitive to characterize the properties of particles-filled composites there we try to exhibit the CB dispersion ratio in immiscible blends through rheological methods. The results from the rheological method show that the majority of CB is found to locate in LLDPE phase, and the minority of CB is also found in EMA phase. Finally, the relationship between the dispersion ratio and CB content is established to predict the distribution concentration of CB in every phase is given.Thirdly, as the percolation threshold of composites would be decreased by using the immiscible blends as matrixes, there is no other characterization to confirm the formation of conductive network in immiscible matrixes. And rheological method is also found to be reasonable to characterize the three-mensional CB network. The percolation curves were also existed in rheological curves (rheological modulus versus CB content), which is called as"viscoelastic percolation". There are similarity between the viscoelastic percolation and electrical percolation. The Nielsen equation is employed to illustrate the agglomeration state of CB. It is found that the agglomeration of CB change greatly in similar content of viscoelastic percolation, which demonstrates the formation of CB conductive network.Finally, the polymer PTC materials with low temperature turn-up have also been developed in the work. The new PTC materials have been testing under all kind of electrical condition, and it is found to be suitable in industrial field. This new product is leading level in domestic field.