Carbon Black--polyethylene Composites Studied by Positron Annihilation

Preliminary results of positron annihilation lifetime measurements, performed for carbon black-LDPE composites with three kinds of carbon black (PRINTEX XE2, VULCAN XC-72, and SAKAP 6) are presented. Four components with lifetimes τ$\text{}_{1}$≈ 120 ps, τ$\text{}_{2}$≈340 ps, τ$\text{}_{3}$≈1.2 ns, τ$\text{}_{4}$≈2.8 ns occurred to be the best fitted to measured positron lifetime spectra. The presence of carbon black resulted only in reduction of intensities of the components with the lifetimes τ$\text{}_{1}$, τ$\text{}_{3}$, τ$\text{}_{4}$ (originating in our opinion from the annihilation of the positronium) and increase in the intensity of the component with the lifetime τ$\text{}_{2}$. The intensities depend both on the content of carbon black 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 intensities which correlate well with the results of studies of resistivity and tensile strength for the same samples.