Crosslinking of poly(vinyl alcohol) via bis(β-hydroxyethyl) sulfone

Poly(vinyl alcohol) (PVA) was crosslinked via bis(beta-hydroxyethyl) sulfone (BHES) at elevated temperatures to improve the water resistance. The best conditions for the crosslinking such as temperature, heat-treatment period, and amount of BHES or catalyst were screened out. Water resistance of the crosslinked PVA was characterized in terms of swelling and weight loss in water. The addition of BHES into PVA followed by heating at elevated temperature resulted in successful formation of crosslinking structure. The crosslinking occurs above 160degreesC and takes shorter period at high temperature than low temperature. The crosslinking catalyst, sodium carbonate, acts more effectively at 160degreesC than at 200degreesC. The results from thermal analysis using a differential scanning calorimetry revealed that the catalyst functions against BHES to lower the temperature for the crosslinking reaction and that even the crosslinked films have the PVA crystalline. The crosslinking procedure using BHES and sodium carbonate is applicable to form ion-exchange fibers based on PVA with high water resistance.