HEAT-RESISTANCE POLY(VINYL ALCOHOL) HYDROGEL

Six methods were used to evaluate the heat resistance of poly(vinyl al cohol) (PVA) hydrogel prepared by a combination of electron beam irrad iation and acetalization of PVA. The physical properties of the hydrog el depended on the degree of acetalization which was affected by conte nt of water in PVA sheet of acetalization in formaldehyde solution at 60 degrees C. It was found that the optimum water content was 20-30%. The acetalized PVA sheet gave maximum tensile strength in electron bea ms irradiation at 100 kGy. The tensile strength of the hydrogel film i ncreased to 20 MPa from 14 MPa by the irradiation. Heat resistance of the hydrogel was evaluated by measuring the mechanical properties afte r sterilization in a steam autoclave at 121 degrees C for 90 min. The tensile strength decreased to 10 MPa whereas the elongation at break i ncreased to 300%. The tackiness of the hydrogel was improved by radiat ion grafting of acrylic acid. Wholesomeness of the hydrogel as a wound dressing was evaluated by attaching to a burn or wound of the back sk in of marmots. Advantages of the hydrogel over a gauze dressing were h omogeneous adhesion to the affected parts, easy removal without damage to renewed skin and slightly faster rate of reconstruction of the inj ured skin.