UTILIZATION OF PINE KRAFT LIGNIN IN STARCH COMPOSITES - IMPACT OF STRUCTURAL HETEROGENEITY

To elucidate the effect of lignin structure on the properties of ligni n-starch composites, an industrial pine kraft lignin sample was fracti onated by sequential extraction with organic solvents. Three fractions were obtained with different carbohydrate contents, infrared spectra, and molecular size distributions. In addition, an in-depth structural investigation was performed by GC-MS analyses of the low-molecular we ight phenolics occurring in the native fractions or obtained by thioac idolysis. The properties of the lignin-starch composites made from pin e kraft lignin or its fractions were evaluated, as compared to referen ce starch films. Although present in small quantities, the low-molecul ar weight fraction isolated from pine kraft lignin was observed to hav e a key role in the mechanical properties of the films, mainly as a st arch plasticizer.