The effect of monomer structure in styrene polymers on the resistance towards PD in air

Styrene polymers were used to study the influence of chemical structure on resistance to PD (partial discharges). It was found that the monomer structure has a great influence on the PD stability. The behavior can be explained by the ease with which radicals are formed. The driving force for the formation of radicals during the degradation is enhanced by electron-donating substituents by the stabilization of benzylic type radicals. Copolymerization of styrene with p-phenylstyrene and 2-vinylnaphthalene (1-20 wt%) produced polymers with higher PD-stability than PS. This demonstrates that the size of the aromatic system is a positive factor regarding PD resistance and that typical voltage stabilizers may also be effective when they are chemically bonded to the main chain.<>