Studies on Oxalic Acid as a Crosslinker of Polyvinyl Alcohol
The suitability of oxalic acid as a crosslinker of polyvinyl alcohol (PVA) is the focus of study of the present paper. Oxalic acid concentration was varied from 3–70% (w/w with respect to polymer) and curing was carried out at various temperatures (100–140 °C) for a range of time periods (20–120 minutes). The optimum curative dose and curing conditions were evaluated through systematic swelling studies (% swelling, gel content, swelling ratio and molecular weight between the crosslinks) of the oxalic acid-treated PVA films, both in hot and cold water. Thermogravimetric analysis showed higher heat stability of oxalic acid crosslinked PVA film compared with heat-treated and virgin PVA. The shift in glass transition temperature (from that of virgin PVA 86 °C) to a higher value for heat-treated and oxalic acid-treated PVA was more prominent for the former than the later. Crosslinking enhanced the Young's modulus and IR spectra indicate the formation of ester carbonyl group in crosslinked PVA.