Carbon black-polyethylene composites studied by positron annihilation

Preliminary results of positron annihilation lifetime measurements, perform ed for carbon black-LDPE composites with three kinds of carbon black (PRINT EX XE2, VULCAN XC-72, and SAKAP 6) are presented. Four components with life times tau(1) approximate to 120 ps, tau(2) approximate to 340 ps, tau(3) ap proximate to 1.2 ns, tau(4) approximate to 2.8 ns occurred to be the best f itted to measured positron lifetime spectra. The presence of carbon black r esulted only in reduction of intensities of the components with the lifetim es tau(1), tau(3), tau(4) (originating in our opinion from the annihilation of the positronium) and increase in the intensity of the component with th e lifetime tau(2). The intensities depend both on the content of carbon bla ck and its kind as well. The strongest influence of the carbon black of the highest specific surface area (PRINTEX XE2) has been observed at the inten sities which correlate well with the results of studies of resistivity and tensile strength for the same samples.