Long-term Oxidative Degradation of Electron Beam Irradiated High Density Polyethylene Studied by Positron Annihilation Technique

Structural change and degradation of electron-beam irradiated high density polyethylene was investigated by a conventional positron annihilation lifetime spectroscopy (PALS) using 22Na positron source, gel fraction measurement, and micro-FT-IR spectroscopy immediately after the irradiation and after 3 years storage in air. The pick-off annihilation intensity of ortho-positronium (o-Ps) became small by the irradiation and after the storage maybe due to the trapping of positron by radicals/carbonyl groups. On the other hand, o-Ps lifetime did not change by the irradiation and the storage. It suggests that size of nanometer-sized free-volume is not affected by the structural change such as oxidation and cross-linking.The 13th meeting of the “Ionizing Radiation and Polymers” symposium (IRaP2018

Synthesis of heat-resistant fish gelatin gel by radiation-induced crosslinking

Gelatin is a kind of protein obtained by the partial hydrolysis of collagen derived from bone, skin and scale of animals such as porcine, bovine, and fish. It has been widely used as gelling agent in many fields such as food, cosmetic, pharmaceutical, and medical because of its multifunctional continent: biological origin, non-antigenicity, biocompatibility and biodegradability. In recent years, there are many researches that improve the heat-resistant at 37 °C and gel strength of porcine and bovine gelatin through the crosslinking by irradiation method without toxic chemicals as crosslinker, their elastic modulus were insufficient for the practical use of biomedical device (10 - 100 kPa). However, products made of mammalian gelatins have concern with ethic problem or religious issue for clinical medicine and tissue engineering. From this necessary demand, fish gelatin can replace and resolve this disadvantage of porcine and bovine ones. Although melting point of fish gelatin gel was lower than mammalian one, recently, it have been reported successfully obtained gelatin having high melting point of 24 °C from Tilapia fish scale by pre-treatment. In this work, hydrogels derived from fish gelatin with different molecular weights were produced by quantum beam in order to improve their heat-resistant, production yields and mechanical property.The 13th meeting of the “Ionizing Radiation and Polymers” symposium (IRaP2018