Positron annihilation in carbon black-polymer composites

Positron lifetime spectra and Doppler broadening of the annihilation line w ere measured for samples of carbon black/polyethylene and polypropylene com posites with varying amount of the filler. Tensile strength, resistivity, E PR resonance were studied in addition to have the samples better characteri zed. The decrease in resistivity of samples, accompanied by the worsening o f mechanical properties, the drop both in the intensities of Ps lifetime co mponents in the lifetime spectra and in the line-shape parameter values, we re observed with increase in the carbon black content. The presence of radi cals associated with aromatic structure of the carbon sheets and others ass ociated with the surface oxygen functional groups was established by EPR me asurements for the carbon blacks being used as fillers. The carbon black of the highest specific surface area influenced the measured characteristics the most. (C) 2000 Elsevier Science Ltd. All rights reserved.