The role of the surface microstructure of the microfibrils in an electrically conductive microfibrillar carbon black/poly(ethylene terephthalate)/polyethylene composite

Carbon black (CB) loading greatly affects the in-situ fibrillation of CB/poly (ethylene terephthalate) (PET) compound in a polyethylene (PE) matrix during melt mixing, slit die extrusion and hot stretching. CB/PET/PE composites with lower CB loadings display well-defined CB/PET microfibrils in which all the CB particles are localized. The surface microstructure (mainly amount and distribution of CB particles) of in-situ CB/PET microfibrils is a key factor determining the electrical conductivity of the microfibrillar composite, and is dominated by the CB content in the in-situ CB/PET microfibrils. With low CB content, there are hardly any CB particles on the surface of the CB/PET microfibril. The volume resistivity of in-situ microfibrillar composite remains high. With higher CB loading, the number of CB particles on the surfaces of the microfibrils increases significantly. Above a critical value (maximum packing fraction), the microfibril network was connected by electrically conductive contact points and thus was able to sustain electron transmission in the whole system. As a result, the volume resistivity of in-situ microfibrillar CB/PET/PE composite dropped sharply and percolation occurred.