Positron lifetime spectra for general purpose polystyrene (GPPS), polybutad
iene rubber (PBR), and their copolymers, styrenebutadiene rubber (SBR) and
high impact polystyrene (HIPS) have been measured. It has been found that t
he free Volumes in the copolymers are smaller than the average over the ind
ividual polymers, due to the interfacial interaction between the styrene an
d rubber phases. A long-lived component with a mean lifetime of about 123 n
s was observed in the spectrum for deformed HIPS, showing the existence of
ortho-positronium (o-Ps) in the deformation induced crazes. (C) 2000 Elsevi
er Science Ltd. All rights reserved.