Effects of a Hindered Amine Stabilizer (HAS) on radiolytic and thermal stability of poly(methyl methacrylate)

Abstract

AbstractCommercial Poly(methyl methacrylate) (PMMA) containing Tinuvin 622, a Hindered Amine Stabilizer (HAS), in 0.3% (wt/wt) concentration was investigated. The samples were irradiated with gamma radiation (60Co) at room temperature in air. The viscosity‐average molecular weight (Mv) was analyzed by viscosity technique. Both control PMMA (without HAS) and PMMA + 622 (with HAS) showed a decrease in molecular weight with the increase in dose, reflecting the random scissions that occurred in the main chain. The G value (scissions/100 eV of energy transferred to the system) was also obtained by viscosity analysis. G value results showed that the addition of Tinuvin 622 into the PMMA matrix significantly decreased the number of scissions/100 eV at dose range of 0–60 kGy. Analysis of infrared spectra showed a decrease in the carbonyl index (CI) in irradiated samples. However the CI decrease was found lower for PMMA + 622 than for control PMMA sample. Thermogravimetric analysis (TGA) revealed that maximum decomposition temperature of additive PMMA is 42°C higher than control PMMA for unirradiated system. On the other hand this difference is not significant in irradiated systems at 60‐kGy irradiation dose. The activation energy of the thermal degradation of PMMA was 165 kJ/mol, this activation energy increased 60 kJ/mol when Tinuvin 622 was added to PMMA matrix. Therefore Tinuvin 622 is a suitable radiostabilizing agent for commercial PMMA in a 0–60 kGy dose interval. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008