Lignin-poly (vinyl alcohol) blends studied by thermal analysis

Alkaline lignin was isolated from sugar cane bagasse for polyblends preparation with three poly (vinyl alcohol) (PVAI) samples (80, 87 and 98% hydrolyzed). Blends preparation was carried out by thorough manual grinding the solid polymer powders, and for one system a comparison was made with blends prepared without grinding. The resulting blends were studied by thermal analysis (TGA and DSC). Miscibility evaluation by T-g determination was possible only in some extent because it was not clearly detected in all cases. These results suggest at least some miscibility of the lignin/PVA180 and lignin/PVA187 systems and immiscibility of the lignin/PVA198 blend. Differences were observed in the properties of the blends prepared with and without grinding. Apparent activation energy of pyrolysis reaction (E-a) were evaluated from TGA curves for pure polymers and blends. E-a of PVAI increases with increasing acetate group content. E-a of the blends suggest a dependence of thermal stability on the hydrolysis degree of the PVAI. Other parameters obtained from TGA and DSC curves were also analysed. (C) 1999 Elsevier Science Ltd. All rights reserved.