Effect of bark flour on the mechanical properties of HDPE composites

Abstract

The objective of this study was to evaluate the replacement of wood flour by Turkish pine bark residues for production of wood plastic composites. High density polyethylene was chosen as matrix and seven different compositions were used for production of composites. In order to compare the effect of bark residues flour as a filler, bark residues-HDPE composites were produced with various wt% bark residues loading (10, 20, 30 and 40 wt%). Bark residues filled HDPE pellets were produced by using a twin-screw extruder, then 25 cm (l) x 25 cm (w) and 2 mm (t) composites were produced with compression molding technique according to ASTM D4703-10. For each composition, three composites were produced. Tensile and flexural tests were performed with a Universal Testing machine. Impact strength was measured with a Zwick HIT5.5P Impact Testing machine. Tensile and impact strength of the composites decreased with increasing bark flour loading whereas bending strength and modulus of eleasticity values were improved with addition of the bark flour. All produced bark flour filled composites showed better modulus of elasticity and bending strength properties than ASTM D6662-13 standard requirements for polyolefin-based plastic lumber. Morphological properties of bark residues-HDPE composites were characterized by scanning electron microscopy (SEM) technique.