Unmodified and Esterified Kraft Lignin-Filled Polyethylene Composites: Compatibilization by Free-Radical Grafting

In this study, the effectiveness of free-radical grafting as a compatibilization method applied to composites containing Kraft lignin (KL) and esterified lignin was comparatively investigated. Maleated lignin (ML) was first obtained via esterification of KL with maleic anhydride. KL and ML were respectively incorporated into high density polyethylene (HDPE) up to 60% wt and dicumyl peroxide was used as a free-radical generator. The influence of lignin esterification and free-radical grafting on the morphological, mechanical, and thermal properties of lignin-based composites was studied. The incorporation of lignins into HDPE resulted in poor mechanical strength because of low compatibility. Morphological and mechanical evidences indicate improved compatibility between lignins and HDPE following free-radical grafting. The free-radical scavenging properties of KL allowed better compatibilization of KL-based composites compared with ML-based composites. In addition, thermal analysis results showed that free-radical grafting increases the thermal stability of ML-based composites. (C) 2014 Wiley Periodicals, Inc.