Discoloration Effects of High-Dose γ-Irradiation and Long-Term Thermal Aging of (U)HMW-PE

Abstract

Two polyethylene types with ultra-high (UHMW-PE) and high molecular weight (HMW-PE) used as neutron radiation shielding materials in casks for radioactive waste were irradiated with doses up to 600 kGy using a 60 Co gamma source. Subsequently, thermal aging at 125∘ C was applied for up to one year. Degradation effects in the materials were characterized using colorimetry, UV-Vis spectroscopy, IR spectroscopy, and DSC. Both materials exhibited a yellowing upon irradiation. The discoloration of UHMW-PE disappeared again after thermal aging. Therefore, the yellowing is assumed to originate from annealable color centers in the form of free radicals that are trapped in the crystalline regions of the polymer and recombine at elevated temperatures. For the antioxidantcontaining HMW-PE, yellowing was observed after both irradiation and thermal aging. The color change was correlated mainly to decomposition products of the antioxidant in addition to trapped radicals as in UHMW-PE. Additionally, black spots appeared after thermal aging of HMW-PE.

Ultra-High-Molecular-Weight-Polyethylene (UHMWPE) as a Promising Polymer Material for Biomedical Applications: A Concise Review

“…Multiple factors influenced the crystallinity and oxidative degradation by irradiation [61,62]. The dose and dose rate of irradiation strongly influence the crystallinity and oxidation of UHMWPE [55,[63][64][65][66][67][68][69]. A suitable post-irradiation process eliminates free radicals to prevent degradation of UHMWPE over the long period and to promote the stability against oxidation.…”

Evaluation of the Degradation of Materials by Exposure to Germicide UV-C Light Through Colorimetry, Tensile Strength and Surface Microstructure Analyses

“…When analyzing the UV-C light effect over the polymers, it was observed that this kind of material tended to get a yellowish color after some exposure time, as occurred in variety of polymers in other works [18][19][20][21]. This behavior was observed not only visually but also quantitatively.…”

A Comparative Study of Gamma-Ray Irradiation-Induced Oxidation: Polyethylene, Poly (Vinylidene Fluoride), and Polytetrafluoroethylene

“…Polyethylene (PE) is used largely in the radiation-technology industry; therefore, the effects of ionizing radiation on it have been extensively studied [ 16 , 17 , 18 ]. Fluoropolymers exhibit excellent chemical/thermal properties and weathering due to the high bonding energy of carbon and fluorine, and the high values of fluorine electronegativity and electron density [ 19 , 20 , 21 ].…”