Characteristics of HDPE/cardboard dust 3D printable composite filaments

In the field of 3D printing, new composites made from blends of natural materials and synthetic polymers have been emerging. In this research, 3D printable composite filaments made with the addition of 20, 50 and 75 wt% cardboard dust to HDPE polymer were analyzed. The influence of including cardboard dust into polymer matrix on the technological, morphological and mechanical properties of filaments was investigated. The addition of 20 wt% cardboard dust had a negligible influence on the diameter and density of the filament. Adding larger quantities of cardboard dust resulted in a substantially larger diameter and essentially lower density. SEM image analysis confirmed high porosity and nonuniformity of the structure. The FTIR spectra analysis revealed a decrease in crystallinity with increased content of cardboard dust present in the filament. According to DMA results, glass transition temperature (Tg) and storage moduli (E') of samples decreased with increased percentage of cardboard dust in HDPE matrix. In the filaments, loss moduli (E '') were low and peaks relatively undistinctive; composite filaments were hence less prone to a plastic deformation than pure HDPE filament. They also showed higher values of tan S. which suggested a more intensive movement of structural elements and higher ability of damping. The mechanical properties declined; elastic moduli, tenacity, strain and stiffness of filaments lowered already at the addition of 20 wt% cardboard dust. Adding 50 and 75 wt% cardboard dust led to much lower tenacity and toughness, low deformability, resulting in the brittleness of filaments. Nevertheless, it was also established that 3D objects could be printed even with 50 wt% cardboard dust/HDPE filament. The research showed that the production of 3D printable composite filaments is feasible; however, the quantity optimization of fillers which is blended with HDPE polymer to reach good mechanical properties is required.