Studies on the thermal stability and film irradiation effect of poly(vinylalcohol)/kraft lignin blends

Lignin and poly(vinylalcohol) (PVA) solutions were separately prepared and then mixed in appropriate ratios, to yield the films after solvent (DMSO) evaporation. Two lignin samples were used: kraft lignin (KL) and acetone soluble fraction of kraft lignin (AKL). Different carbonyl and hydroxyl contents were detected by (HNMR)-H-1 and by FTIR for KL and AKL. PVA films containing up to 25% of lignin were prepared and irradiated with UV light for different time intervals. These films were analyzed using FTIR, TG and DSC. Due to the lignin incorporation in PVA films an increase in the thermal stability was observed. From DSC experiments, PVA/KL seems to provide a more homogeneous material compared to PVA/AKL, especially at 95/5 composition. PVA/KL films seem to have greater resistance to photochemical attack, as evaluated by crystallinity changes after irradiation of the film.