Recycled Polystyrene Composites Reinforced With Esterified and Non-Esterified Kraft Lignins

Abstract

Recycled polystyrene and Kraft lignins represent waste materials/by-products, generated in huge quantities worldwide, which remain inadequately valorized. In this study, unmodified and maleated Kraft lignins were used as fillers in recycled polystyrene (RPS) to produce composites at different concentrations (0, 10, 20 and 30%) via melt blending. Also, RPS composites with 20% of maleated Kraft lignins were prepared by applying a previous surface treatment to the maleated Kraft lignins with RPS in solution. A complete mechanical, thermal and morphological characterization was performed on the RPS based composites containing Kraft lignins. The morphological study revealed better compatibility with RPS for unmodified Kraft lignins than maleated Kraft lignins except for the composite where maleated lignins surface treatment was applied. In this case, the RPS was well incorporated in the porous structure of maleated Kraft lignins. The results also showed that addition of unmodified Kraft lignins led to better mechanical and thermal properties of the composites than when maleated Kraft lignins were added. For the composite formulated with 20% maleated Kraft lignins with a previous surface treatment, the properties were improved to become comparable to those of composites with unmodified Kraft lignins. The poor mechanical and thermal properties of RPS composites with maleated Kraft lignins could be related to the porous structure of the maleated Kraft lignins.