Radiation effects on polystyrene/ethylene-propylene copolymers compounds

The electric behaviour of binary polystyrene/ethylene-propylene copolymers (EPR) and EPDM) was studied. The tested compounds of various compositions (75:25, 50:50, and 25:75) were gamma irradiated at room temperature. The degradation process was accompanied by changes in the electric characteristics, for example: dielectric constant, dielectric loss, and volume resistivity. These parameters were influenced either by the chemical nature of the compounding components or by the total absorbed dose. Polystyrene has acted as a scavenger for electrical charges generated by the energy transfer from gamma radiation to the studied polymers. The decrease of permittivity and volume resistivity and, at the same time, the increase of dielectric loss has suggested that the absorbed dose was directed to the polymer scission process accompanied or followed by the electron ejection. The new entities may be linked to the radical acceptor sites, probably by an electrophilic substitution. The correlation between the modification of chemical structure and the consequences of radiation action on the tested compounds was discussed. (author) 4 figs., 20 refs