A study has been made of the non-isothermal crystallization behavior and thermal transitions of a biodegradable, partially hydrolyzed poly(vinyl alcohol) with 80% degree of saponification (PVA80). Possible sample degradation was first investigated, but no significant degradation or dehydration was detected using FTFIR and DSC under the experimental condition. The non-isothermal crystallization of PVA80 was analyzed with Ozawa equation, and the Mo method of combining Ozawa and Avrami equations. Ozawa equation was only applicable in a narrow temperature range from 80 to 100 degrees C. The deviation from the Ozawa equation is not due to the secondary crystallization or the quasi-isothermal nature of the treatment. It is only a result of the large relative difference of the relative crystallinity values under different cooling rates. The Mo method demonstrated a success in the full temperature range investigated. The isoconversional method developed by Friedman failed to estimate the activation energy for this non-isothermal crystallization. Thermal transitions of PVA80 are associated with its complex hydrogen-bonding interactions. The melt-crystallized PVA80 sample, as that from film casting, followed by annealing at 60 and 80 degrees C, has a broad melting temperature range measured by DSC and FTIR. It was found that the melting behavior of a semicrystalline polymer can be probed via a noncrystalline hydrogen-bonded C=O band using FTIR. The glass transition temperature T-g of PVA80 was raised about 20 degrees C, after the sample was melt-crystallized. The intensity of the hydrogen-bonded C=O band increases when temperature was increased from 110 to 180 degrees C, due to the promoted hydrogen-bonding interactions between the C=O groups in the amorphous phase and the hydroxyl groups from the crystalline phase, which is also the main reason for the increased T-g transition. (c) 2006 Elsevier Ltd. All rights reserved.