(167a) Hybrid biocomposites of polypropylene reinforced with pyrolyzed soyhull meal micro-particles and graphene nanoplatelets

In recent years, the incorporation of biobased carbon (BioC) fillers into polyolefins or biodegradable polymers have been studied with many researchers. BioC is produced by pyrolysis of lignocellulosic material in the absence of oxygen, resulting in the formation of syngas, bio-oil and BioC. In this study, polypropylene (PP) was blended with 20 wt.% soyhull meal BioC (pyrolyzed at 500^oC) by melt extrusion followed by injection moulding at 180^oC. To enhance the compatibility between the matrix and the filler, maleic anhydride grafted polypropylene (MA-g-PP) (3 wt.%) was used as a compatibilizer for enhancing the interfacial adhesion in the composites. Moreover, graphene nanoplatelets (GnPs) have been incorporated, at loadings of 0.5, 1, 3 and 5 wt.%, as a nanofiller to enhance the mechanical and thermal properties of the final product. The incorporation of MA-g-PP and GnPs enhanced the tensile strength and modulus by ~41% and ~21%, respectively. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed a good dispersion of BioC in the presence of MA-g-PP, where significant GnPs agglomeration was identified. The thermal stability of the hybrid biocomposites was enhanced by the incorporation of both BioC and GnPs, as observed through TGA characterization. Moreover, the coefficient of linear thermal expansion of the hybrid biocomposites was decreased by around 20% compared to neat PP by the inclusion of both fillers. Overall, the hybridization of BioC and a small amount of GnPs present a promising route to augment the thermal and mechanical properties of polyolefins while reducing dependence on petroleum products.

Acknowledgements: The authors are thankful for the financial support of (i) the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA)/University of Guelph – Bioeconomy for Industrial Uses Research Program (Project #030332); (ii) the Natural Sciences and Engineering Research Council (NSERC), Canada Discovery Grants (Project #400320 and 401111); (iii) the Ontario Research Fund, Research Excellence Program; Round 7 (ORF-RE07) from the Ontario Ministry of Research, Innovation and Science (MRIS) (Project #052644 and 052665) in carrying out this research.