Plasticizer effect on the melting and crystallization behavior of polyvinyl alcohol

The melting and crystallization behavior of polyvinyl alcohol (PVA) were examined as a function of plasticizer amount. The melting temperature (T-m) of PVA decreased with increasing the amount of glycerin. The effect of a plasticizer rapidly diminished when the phase separation of glycerin in PVA occurred. In addition, the crystallization peak temperature (T-c) of a fully hydrolysed PVA was reduced, and the maximum crystallization rate (K-max) was retarded, and the crystallite size distribution (omega(1/2)) was widened. However, the crystallization behavior (T-c, K-max, omega(1/2)) of a partially hydrolysed PVA could be disregarded compared with a fully hydrolysed PVA. The thermal history did not affect the crystallization behavior of a fully hydrolysed PVA, but largely affected that of a partially hydrolysed PVA. In a fully hydrolysed PVA/a partially hydrolysed PVA blend system, two T-m peaks appeared, and the concurrent crystallization occurred. (C) 2003 Elsevier Ltd. All rights reserved.