Construction and foamability of lignin-reinforced low-density polyethylene biocomposites

Lignin was chemically modified with poly(ethylene-co-glycidyl methacrylate) copolymer (PEGMA) to form PEGMA-grafted lignin (PEGMA-g-lignin). The pristine lignin and PEGMA-g-lignin were successfully incorporated into a low-density polyethylene (LDPE) matrix. In the PEGMA-g-lignin/LDPE biocomposites, interfacial adhesion between the lignin particles and the LDPE matrix was better and stronger than that between the lignin particles and the LDPE matrix in pristine lignin/LDPE biocomposites. Analyses of the thermal behaviors and mechanical properties of the resultant biocomposites revealed that enhanced mechanical properties could be achieved without affecting the thermal characteristics of the LDPE matrix. Moreover, foamability of the biocomposites was studied in the presence of azodicarbonamide (chemical blowing agent) and dicumyl peroxide (crosslinking agent). The introduction of 20 wt.-% PEGMA-g-lignin led to good quality lignin-reinforced LDPE biocomposite foams, where the cell size frequency distribution of the resultant foams was uniform and the cell density and foam expansion were similar to those of neat LDPE foam.