화학공학소재연구정보센터
Journal of Applied Polymer Science, Vol.81, No.1, 104-115, 2001
Electrical behavior and structure of polypropylene/ultrahigh molecular weight polyethylene/carbon black immiscible blends
This study investigates the electrical behavior, which is the positive temperature coefficient/negative temperature coefficient (PTC/NTC) and structure of polypropylene (PP)/ultrahigh molecular weight polyethylene (UHMWPE)/carbon black (CB) and PP/gamma irradiated UHMWPE (XL-UHMWPE)/CB blends. As-received UHMWPE or XL-UHMWPE particles are chosen as the dispersed phase because of their unusual structural and rheological properties (extremely high viscosity), which practically prevent CB particles penetration. Because of their stronger affinity to PE, CB particles initially form conductive networks in the UHMWPE phase, followed by distribution in the PP matrix. thus interconnecting the CB-covered UHMWPE particles. This unusual CB distribution results in a reduced electrical percolation threshold and also a double-PTC effect. The blends are also investigated as filaments for the effect of shear rate and processing temperature on their electrical properties using a capillary rheometer. Because of the different morphologies of the, as-received and XL-UHMWPE: particles in the filaments, the UHMWPE containing blends exhibit unpredictable resistivities with increasing shear rates, while their XL-UHMWPE containing counterparts depict more stable trends. The different electrical properties of the produced filaments are also related to differences in the rheological behavior of PP/UHMWPE/CB and PP/XL-UHMWPE/CB blends. Although the flow mechanism of the former blend is attributed to polymer viscous flow, the latter is attributed to particle slippage effects.