Injection molded biocomposites from polypropylene and lignin: Effect of compatibilizers on interfacial adhesion and performance

This study compares the effect of two compatibilizers on polypropylene (PP)-lignin composites. Two commercial compatibilizers: maleated polypropylene (MAPP) and ethylene butylacrylate glycidylmethacrylate (EBGMA), as well combinations of them, were used to enhance the interfacial adhesion of PP/lignin composites. The main advantage of the use of lignin as a filler in value-added composites is its great natural abundance. Polymer composites were prepared by using reactive extrusion and injection molding techniques in order to examine the effect of interfacial adhesion on the thermo-mechanical properties of PP. The incorporation of MAPP led to improvements in tensile strength, while the incorporation of EBGMA led to improvements in impact strength. The mixture of both compatibilizer type improved both tensile and impact strength. Addition of compatibilizer to the composites also showed an enhancement to the interfacial adhesion, as investigated by scanning electron microscopy (SEM). FTIR analysis revealed an intermolecular reaction between the compatibilizer and lignin via relevant hydroxyl groups. The water absorption decreased by incorporation of the compatibilizer.