Thermo-electric behavior (PTC) of carbon black-containing PVDF/UHMWPE and PVDF/XL-UHMWPE blends

This paper describes the structure and electrical performance of PTC/NTC (positive temperature coefficient/negative temperature coefficient) effects and their reproducibility upon heating/cooling cycles. The following three-component blends were studied: PVDF/UHMWPE/CB, PVDF/XL-UHMWPE/CB and gamma -irradiated compression molded plaques of these blends. Carbon black (CB) particles are attracted to the UHMWPE (ultra high molecular weight polyethylene) and XL (cross-linked)UHMWPE particles, which constitute the dispersed phase in the PVDF (polyvinylidene fluoride) matrix, but practically cannot or only very slightly penetrate them because of their extremely high viscosity. A double-PTC effect was exhibited by all unirradiated samples. Irradiation of compression molded PVDF/UHMWPE/CB plaques does not add to their already outstanding reproducibility, and it results in a wide single-PTC effect. Irradiation of compression molded PVDF/XL-UHMWPE/CB plaques stabilizes their structure upon heating/cooling cycles and thus makes them reproducible PTC/NTC materials, still exhibiting a double-PTC effect. The carbon black concentrations studied in this report are extremely low (< 2 phr CB) in comparison to other literature reports.