Use of pencil slat and graphite pencil shavings as reinforcing filler in thermoplastic composites

The objective of this study was to investigate the potential use of the graphite pencil shavings in wood-plastic composites (WPCs). Physical, mechanical, and thermal properties of the WPCs made with graphite pencil shavings were also compared with the WPCs made with pencil slat shavings without graphite. Different contents (0-50 wt%, in 10 wt% increments) of the pencil slat shavings and graphite/colour pencil shavings, by-products of the pencil manufacturer, were separately added to the polypropylene matrix with 3 wt% compatibilizers. The water resistance of the WPCs decreased with increasing filler content. The bending modulus of the WPCs was significantly enhanced with the incorporation of both fillers up to 50 wt%, while this ratio was 40 wt% for the bending strength. Although the WPC's tensile strength tended to decrease with increasing filler content above 20 wt%, it exceeded 29 MPa, tensile strength of pure polypropylene, up to 30 wt% filler content. Thermal stability of the WPCs increased with the addition of the filler. When evaluating the test results of the WPCs, it is recommended that the filler content should be 20 wt%, depending on the performance expectations of the end user.