LF-NMR analysis of the water mobility, state and distribution in sorbitol plasticized polyvinyl alcohol films

In this work, high-alcoholysis polyvinyl alcohol (PVA) films with sorbitol as plasticizer are obtained through the melt processing and characterized with low field nuclear magnetic resonance (LF-NMR), differential scanning calorimetry (DSC) etc. to investigate the water mobility, state and distribution as well as its effect on the performance of the films. The results show that two state of water, e.g. bound water and free water, exist and sorbitol can effectively bind w'ater in PVA films. The sorbitol molecules can effectively promote the formation of bound water. Therefore, with the increase of sorbitol plasticizer, the bound water content increases. The water migration study indicates that sorbitol can form strong hydrogen bonds with water and make the bound water more stable. The tensile strength and the haze of the films increase with increased bound water content.