Radiation grafting of hydrophilic monomers on to plasticized poly(vinyl chloride) sheets

Abstract

Medical-grade plasticized poly(vinyl chloride) (PVC) sheets were surface modified using gamma-radiation grafting of a combination of hydrophilic monomers based on 2-hydroxyethyl methacrylate (HEMA) and N-vinyl pyrrolidone (NVP). The modified surfaces were evaluated for their surface properties using contact angle measurements, phase-contrast photomicroscopy and scanning electron microscopy. Surface energy calculations of the modified surfaces indicated that the surfaces became highly hydrophilic when grafted with even a 1% (v/v) solution of HEMA-NVP combination in the presence of 0.005m CuSO₄. Migration of the plasticizer di(2-ethylhexyl phthalate) (DEHP) from the grafted sheets was examined in hydrocarbon solvents such as n-hexane, n-heptane and n-octane and in extractant media such as cotton seed oil and polyethylene glycol-400 (PEG-400). The migration from modified sheets was found to be <4% of the migration from unmodified control sheets in hydrocarbon solvents at 30° c over a period of 5 h. Accelerated leaching studies in cotton seed oil and peg-400 demonstrated that virtually no plasticizer migrated out in the former over a period of 96 h whereas the rate of migration in the latter medium showed only a mild reduction. The migration behaviour was fickian in nature for grafted sheets. The method described may be useful as a simple, versatile technique for preventing plasticizer migration from plasticized pvc for medical applications.