No abstract

High‐density polyethylene (HDPE) is one of the most widely used semi‐crystalline polyolefin thermoplastics. However, 3D printing with this material remains rare because of massive shrinkage and poor adhesion to common 3D printing build surfaces. In this study, shrinkage and warping were overcome by blending in short fibers of yellow birch at 10–30 wt% along with a coupling agent. Square tubes were printed to measure deformation and mechanical properties of this composite material. Deformation was reduced by 80% in material containing 30 wt% wood compared to neat HDPE. Young's modulus increased respectively by 25%, 30%, and 35% as the filler content increased to 10, 20, and 30 wt%. This is the first known successful 3D printing with wood‐fiber HDPE composite.

Wood–plastic composites have emerged and represent an alternative to conventional composites reinforced with synthetic carbon fiber or glass fiber–polymer. A wide variety of wood fibers are used in WPCs including birch fiber. Birch is a common hardwood tree that grows in cool areas such as the province of Quebec, Canada. The effect of the filler proportion on the mechanical properties, wettability, and thermal degradation of high-density polyethylene/birch fiber composite was studied. High-density polyethylene, birch fiber and maleic anhydride polyethylene as coupling agent were mixed and pressed to obtain test specimens. Tensile and flexural tests, scanning electron microscopy, dynamic mechanical analysis, differential scanning calorimetry, thermogravimetry analysis and surface energy measurement were carried out. The tensile elastic modulus increased by 210% as the fiber content reached 50% by weight while the flexural modulus increased by 236%. The water droplet contact angle always exceeded 90°, meaning that the material remained hydrophobic. The thermal decomposition mass loss increased proportional with the percentage of fiber, which degraded at a lower temperature than the HDPE did. Both the storage modulus and the loss modulus increased with the proportion of fiber. Based on differential scanning calorimetry, neither the fiber proportion nor the coupling agent proportion affected the material melting temperature.