Poly(butylene terephthalate)/poly(ethylene-co-alkyl acrylate)/carbon blackconductive composites: Influence of composition and morphology on electrical properties

Poly(butylene terephthalate)/poly(ethylene-co-alkyl-acrylate)/carbon black (PBT-EXA-CB) blends, prepared through extrusion, were characterized as elec trical conductive materials. In the composition range studied (55 less than or equal to PBT % less than or equal to 75 w/w; 5.5 less than or equal to CB % less than or equal to 11.1 w/w), various conductive behaviors were obs erved depending mainly on composition and poly(olefin) crystallinity. The o bserved positive temperature coefficient (PTC) is quite small compared to p oly(olefin)-CB systems, and our blends do not present a negative temperatur e coefficient (NTC) on complete melting of the CB-containing phase, thus of fering new possibilities for a regular electric power control. Volume expan sion of both PBT and EXA was postulated to be the main parameter responsibl e for the thermal resistivity evolution through the range +20 to +170 degre esC. A double-percolation system between both the co-continuous polymer pha ses and CB-particles included in the poly(olefin) phase is postulated to ex plain these results.