Radiation effects in polypropylene/polystyrene blends as the model of aromatic protection effects

A technically useful composition containing polypropylene (PP) as a principal constituent, expected to be working or to be processed in ionizing radiation field, e.g. for sterilization, has to be protected from undesired radiolysis resulting in radiation damage. Usually, conventional additives are used which are generally effective, especially when containing aromatic groups. They can be sometimes unacceptable, e.g. in medical applications. Polystyrene (PS) has been investigated as a protective component, in analogy to the classical case of cyclohexane/benzene system. Mechanical mixing of both polymers showed to be of modest effect, but two other procedures, of soaking polypropylene powder with polystyrene dissolved in styrene, or soaking with styrene and gamma preirradiation with resulting grafting (G = 12.000 effects/100 eV), resulted in the composition of improved resistance towards radiation. The energy transfer, which explains the effect, is extended at a distance of 8-12 mers of polypropylene. The investigations have been made by gas chromatography and diffuse light reflection spectrophotometry (DRS), after 10 MeV electron beam irradiations. (authors)