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 (Tm) 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 (Tc) of a fully hydrolysed PVA was reduced, and the maximum crystallization rate (Kmax) was retarded, and the crystallite size distribution (ω1/2) was widened. However, the crystallization behavior (Tc, Kmax, ω1/2) 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 Tm peaks appeared, and the concurrent crystallization occurred.