Preparation And Properties Of Conductive Composites Based On Poly(Butylene Terephthalate) As Matrix

Conductive polymer composites have been extensively used in many fields, such as electronic, energy and chemical engineering. To ensure a high conductivity, conducting fillers are requested more loading, namely, a high content of the fillers in the composites. A typical example is that it is used to add more than 20% conductive carbon black (CB) in the composite to form conducting network. However, high loadings of fillers lead to high melting viscosity, poor processability and low mechanical properties. Hence, lowering content of conducting filler in a composite is of importance for improving the properties of the composites.A series of conductive polymer composites of CB/poly(butylene terephthalate) (PBT) and ATO/PBT were prepared by melt-mixing method. The conductivity, morphology, resistivity-temperature (R-T) relationship and rheological behevior were investigated.Optical microscope and scanning electron microscope (SEM) were employed to observe the morphology of the conductive composites and the distribution of carbon black in composites. The composites of CB/PBT exhibited a good distribution of the conducting fillers in the matrix via pre-treatment such as adding coupling agents and dispersants and various processing methods. No obvious agglomeration obviously appeared at low loadings of <10wt% CB content, leading to lower percolation threshold and better processibility. The measurement of electrical conductivity of the CB/PBT composites indicated that the composites exhibited the excellent electrical conductivity and the low percolation threshold of 4wt%. Meanwhile, the R-T behaviors of composites showed that the composites of 2wt% CB content appeared L-PTC behavior, while the composites of 4wt% CB content at the loading of percolation threshold appeared L-NTC behavior. The dynamic rheological behavior of CB/PBT composite exhibited a very strong shear thinning effect. At low frequencies, the rheological behavior of the composites gives an obvious dependence of frequency for <6.0wt% CB. At high frequencies, the content of CB has a slight influence on the rheological behavior of the composites. The results indicate a solid-like behavior formed in the composites, suggesting the formation of a CB conducting network.To prepare the light-colored conductive composite, ATO was firstly modified using dispersing agent and coupling agent, and the dispersion of the conducing fillers was analized via the measurement of particle size, PDI and infrared spectra of the products. And then, the conductive composites were prepared by blending ATO with PBT. The morphology of ATO in the polymer matrix was observed by means of optical microscopy and scanning electron microscopy. As a result, the ATO particles can be made more evenly dispersed in the PBT matrix, showing a percolation threshold of about 31wt%. Rheological behavior showed that with increasing ATO, the composite systems showed shear thinning behavior and the conductive network structure was formed.