Complete relaxation map of polyethylene: filler-induced chemical modifications as dielectric probes

Low-density polyethylene (LDPE) filled with a small amount of titanium diox ide proves to be very suitable for studying the molecular motion of polyeth ylene by means of dielectric spectroscopy. The titanium dioxide acts as an oxidizing agent that introduces a small concentration of polar carbonyl gro ups, which does not alter molecular motion, but couples it to the alternati ng electric field. The frequency and temperature dependences of molecular-motion processes in LDPE are determined from both isochronal and isothermal loss plots. In part icular. the temperature dependence of the beta process connected with the g lass-rubber transition in polyethylene obeys the Vogel-Fulcher-Tammann-Hess e law, which indicates co-operative behaviour. For pure LDPE, a glass-trans ition temperature of -31 degreesC is determined dielectrically. It increase s with increasing titanium dioxide content.