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

Abstract

The ability of Tinuvin 622, a Hindered Amine Stabilizer (HAS), in decreasing of radiation damage to commercial PMMA matrix used in manufacturing of medical supplies was examined. Effects of gamma irradiation in PMMA specimens irradiated at dose range of 10-60 kGy were assessed by comparison of the variation of viscosity average molar mass (M v ) of PMMA with Tinuvin 622 (PMMA-622) when compared with PMMA without the additive (PMMA-control). Samples containing Tinuvin 622 presented smaller decrease of M v as a function of dose. This phenomenon causes direct influence in the mechanical properties of PMMA. Above 10 kGy, both PMMA-control and PMMA-622 undergo changes in the yellowness index with increase of absorbed dose; however, the phenomenon was less pronounced for PMMA-622 samples. Electron Spin Resonance spectra showed that Tinuvin 622 induces a faster evolution of radicals formed in PMMA radiolysis followed by a decrease in radiation-induced degradation of the samples.

Study of Commercial Additive Effects on the Poly(methyl methacrylate) Exposed to Gamma Irradiation by Viscosimetric Analysis

“…This result does mean that the scission effect is predominant in the PMMA matrix. Similar results were data for PMMA exposed to gamma irradiation 7,21,40 .…”

“…Besides studying the molar mass of polymers exposed to gamma rays, viscosity analysis provides critical data about the interactions of additives and polymer molecules in solution 21,40 . In this investigation, viscometry parameters of methyl-ethyl-ketone solutions of Poly (methyl methacrylate) and its mixture with commercial additives were obtained by single concentration determinations.…”

“…It is not common to use commercial additives for radiolytic stabilization purposes. However, some studies have already shown this potential 13,21,40 . In a preliminary analysis, the additives shown in Table 4 were analyzed.…”

Sterilization by Gamma Irradiation

“…After 63 days of storage at 30 kGy dose, the yellowness index measured was 2.78 and 0.17 to PMMA-control and PMMA-622, respectively. These results showed that the Tinuvin 622 is a good alternative for stabilizing the PMMA against gamma irradiation damage in sterilization processes with low cost (Aquino et al, 2010) The scheme in Figure 13 is generally accepted to explain the aspects of the chemistry mechanism of HALS action to inhibit polymer photo-oxidation. This scheme was used to guide a strategy to assess Tinuvin 622 action in radiolytic stabilization of PMMA (Aquino & Araujo, 2008).…”

“…Thus the nitroxyl radicals could regenerate many times through the chain reaction before their depletion. The single Electron Spin Resonance (ESR) spectrum was obtained for Tinuvin 622 sample irradiated at 100 kGy and was attributed to nitroxyl radical (Aquino et al, 2010). The chemistry of HALS had been widely documented for UV irradiation.…”