Abstract
Novel elastic gel was obtained by immersing paste of sodium carboxymethylcellulose (CMC) in acid solution. The paste was prepared by mixing CMC and water at the concentration of 20%. Water absorption and mechanical strength of the resultant gel were evaluated after removing uncrosslinked CMC and acid. Combination of radiation crosslinking and the immersion in acid resulted precise molding and dimension stability of the gel. Maximum mechanical strength of the gel at 50% compression increased with acid concentration for the unirradiated and the irradiated samples at 5-20kGy. The gel prepared by irradiation at 5-10kGy and the immersion did not cause rupture after 50% compression and was more than 100 times stronger than the radiation-crosslinked gel. The reason of the mechanical strength was attributed to crosslinks formed by the acid treatment The crosslinks by the irradiation had been referred to chemical bonds, whereas, those by acids were caused by hydrogen bonds, which was elucidated by FT-IR, ICP and TG-DTA measurements. Sodium in the carboxymethyl groups is replaced by hydrogen in the acid solution. The hydrogen bonds induced the decrease of CMC solubility in water and formed the elastic gel.
