Estabilidade à radiaÃÃo gama do poli(cloreto de vinila) aditivado e do poli(cloreto de vinila) quimicamente modificado

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

Poly (vinyl chloride)-PVC is a polar thermoplastic polymer compatible with a wide array of additives, which is used in several practical applications. Among the products made of PVC there are medical devices which need to be sterilized through gamma irradiation. In this work a study was made to evaluate the stability to gamma radiation of PVC additivated, as well as the stability and flexibility of chemically modified PVCs. PVC was chemically modified by the substitution of chlorine atoms by alkyl and benzyl groups through Grignard reagents, by the hydroxibenzyl group through the Barbier reaction in aqueous media, and by diethylene glycol monoethers, through reaction with the respective organolithium reagents. The polymer was also modified through the reduction reaction with zinc. Samples of aditivated PVC films were exposed to gamma radiation and their vicosity parameters, mechanical properties and spectroscopic properties in the ultra-violet region were analyzed to evaluate the impact of irradiation in the polymer. The polymeric systems analyzed were PVC/plasticizer, in which the plasticizers were: DEHP(DOP) di(2-ethylhexyl)phthalate), DIBP (diisobutyl phthalate), TOTM (tris(2- ethylhexyl)trimellitate), Viernol (polymeric plasticizer) PVC/DOP, and the PVC/DOP system stabilized by tinuvin P. It was found that upon irradiation the PVC/plasticizer films degrade by chain scission wich results in lower tensile and percent elongation, as well as increased absorbance at 400nm due to yellowing of the film. The addition of tinuvin P to the PVC/DOP system hindered degradation and minimized the effects of radiation on the mechanical properties of the films. The chemically modified PVCs displayed an increased stability to gamma radiation, except for those modified with diethyleneglicol monoethers. The PVC with the aromatic ring side group presented the highest stability towards gamma irradiation at all dosages. Chemically modified PVCs presented lower glass transition temperatures than the non substituted PVC. So the substitution of distinct side groups on the PVC chain leads to increased flexibility.

ASSUNTO(S)

do poli(cloreto de vinila) - quimicamente modificado quimica poli(cloreto de vinila) - aditivado radiaÃÃo - gama

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