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

Abstract

Commercial 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 ( 60 Co) at room temperature in air. The viscosity-average molecular weight (M v ) was analyzed by viscosity technique. Both control PMMA (without HAS) and PMMA 1 622 (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 1 622 than for control PMMA sample. Thermogravimetric analysis (TGA) revealed that maximum decomposition temperature of additive PMMA is 428C 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.

Influence of a hindered amine stabilizer on optical and mechanical properties of poly(methyl methacrylate) exposed to gamma irradiation

“…These results suggest that PMMA‐control undergoes more thermal degradation in industrial process than PMMA‐622. In addition, the activation energy calculated for thermal degradation of PMMA was 165 kJ/mol, this activation energy increased 60 kJ/mol when Tinuvin 622 was added to PMMA matrix 18. Thus, the PMMA‐622 samples are more thermally stable than PMMA‐control.…”

“…Note that M v decreases continuously with increase of absorbed dose due main chain scission effect. In our previous work,18 we calculated the G values (scission/100 eV) of 2.6 for PMMA‐control and 1.0 for PMMA‐622 at dose range of 0–60 kGy. These results represent 61% of reduction in yield of chain scission in PMMA matrix by Tinuvin 622 action.…”

Use of Lead (II) Sulfide Nanoparticles as Stabilizer for PMMA Exposed to Gamma Irradiation

“…Ours previously study 15 showed that the PMMA in study contains a double bond in the end group, which is formed through radical polymerization of PMMA 34,35 . In general, under inert atmosphere, thermal degradation of double bond-terminated PMMA (PMMA=) prepared by radical polymerization exhibits four main weight losses events, corresponding to four degradation stages 34,35,36 .…”

“…In general, under inert atmosphere, thermal degradation of double bond-terminated PMMA (PMMA=) prepared by radical polymerization exhibits four main weight losses events, corresponding to four degradation stages 34,35,36 . The first stage corresponds to the degradation initiated by radical transfer to the unsaturated chain end; the second and third stages result from the homolytic scission of the chain due to headto-head bonds and degradation initiated by radical transfer to the unsaturated chain end; the fourth stage corresponds to random scissions 15 . TGA thermograms of PMMA and PMMA/PbS-NP (0.3 wt%) are shown in Figure 7a for unirradiated systems.…”

“…, and the behavior of this polymer under radiation has been extensively studied 12,14 , including ours previous studies 15 . PMMA is known to undergo main chain scission when exposed to ionizing radiation.…”