Morphology, Resistivity, and PTC behavior of EVOH/CB composites prepared by solvent-casting saponification and precipitation saponification.

Poly(ethylene- co-vinyl alcohol)/carbon black (EVOH/CB) composites were prepared by a solvent-casting saponification (-D) and precipitation saponification (-P) methods with a poly(ethylene- co-vinyl acetate)/CB (EVA/CB) toluene suspension. The effects of the CB content and saponification time on the morphology, electrical resistivity, thermal, and mechanical properties of EVA/CB composites were examined. The volume resistivity ( ρv) of the EVA/CB-D and EVA/CB-P samples decreased significantly with increasing CB content and the percolation threshold of such composites was determined about 10 wt%. At 10 wt% of CB content, the ρv of EVA/CB-D composite decreased significantly with the saponification time, whereas ρv of EVA/CB-P composites did not change. As the saponification time increased, EVA/CB25wt% composites form cavity structure which CB is usually located in oval cavities larger than the particles themselves. This oval cavity structure almost resembles extruded high-density polyethylene (HDPE)/CB composites. The morphology and PTC behavior of prepared composites were compared with those of HDPE/CB and the mechanism of PTC and NTC effects was discussed. POLYM. COMPOS., 38:1462-1473, 2017. © 2015 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]