Physicochemical properties of PLA lignin blends

Commercial alkali lignin (CL) and lignin extracted from almond shells by organosolv process (OL) were used for the preparation of blends with poly(lactic acid) (PLA) with different percentages (0.5, 1, 5, 10 and 20%) by extrusion method. Both lignins were acetylated to improve their compatibility with PLA. PLA/acetylated lignin blends exhibited greater compatibility than non-acetylated PLA/lignin. Characterization of lignins has been performed using HPLC, FT-IR, GPC, DSC and TGA. All lignins showed high purity. Acetylated lignins had lower Tg and higher thermal stability than original lignins. Thermal and mechanical properties of different blends were investigated. Morphology before and after hydrolytic degradations of blends with 5% of different lignins were also investigated. The addition of acetylated lignin appears to prevent hydrolytic degradation of PLA. Lignin content increased the thermal stability of PLA but does not favor the crystallization of PLA. Maximum strength decreased with high percentages of originals lignins. However, PLA/acetylated lignin blends remains fairly constant, even at high percentages. In all cases, the elongation at break was increased.