Thermal and mechanical properties of unplasticized polyvinyl chloride (UPVC) copolymer irradiated with ion beams

Abstract

In this paper the changes in the thermal and mechanical properties of unplasticized polyvinyl chloride (UPVC) films under ion beams irradiation have been studied. Two series of irradiation were performed; one series irradiated with a constant fluence (2.25×10 9 ions/cm 2) but at different beam energies (25–37 MeV) and another series irradiated at a constant energy (25 MeV) over a wide range of fluence (10 9–10 15 ions/cm 2) . The thermogravimetric analysis (TGA) thermograms showed that the thermal decomposition of UPVC films either before or after ion beams irradiation occurred through two stages. The films were very stable up to ∼500 K, the major weight loss occurred during the temperature range (500–630 K) and a second stage up to 750 K in which the films showed a stability somewhat against thermal decomposition. However, both the irradiated series showed a relatively higher thermal stability than the unirradiated one as indicated from the decomposition temperature at a certain % weight loss. The determination of the kinetic parameters indicates that the thermal decomposition reaction follows zero order reaction with activation energies dependent on the heating temperature and not on the residual mass. For the 25 MeV H + irradiated series, the average activation energy was found to increase from 249 kJ/mol for unirradiated UPVC to 306 kJ/mol for the irradiated films at a fluence of 2.25×10 9 ions/cm 2 . Then, the change in activation energy values for both series was found to occur in a similar trend. In addition, the high energy irradiation process in our energy range of study has no clear effect on the mechanical properties of films. Meanwhile, for the dosed samples, the elongation percent and the yielding point were affected significantly.