Evaluation of Kraft lignin as natural compatibilizer in wood flour/polypropylene composites

This study investigated the effect of Kraft lignin as natural compatibilizer on the water absorption, thermal, mechanical, and interfacial properties of poplar wood flour (WF)/polypropylene (PP) composites. Varying contents (0.5, 1, 2, 4, and 8 wt%) of lignin were added to WF and PP by direct mixing, then the composites were prepared by two‐screw extrusion and compression moulding. Results showed that lignin incorporation reduced the water absorption and postponed the thermal decomposition of the composites. Composites with lower lignin contents (0.5% and 1%) could get the optimal properties, and the excess lignin contents (4% and 8%) resulted in slight decrease in the mechanical properties. DMA and calculation of adhesion factor showed that the composites with 0.5% lignin had the best interaction between WF and PP. The morphologies of fractured surface also indicated improved interfacial adhesion between WF and PP from the addition of 0.5% and 1% lignin. POLYM. COMPOS., 38:2387–2394, 2017. © 2015 Society of Plastics Engineers