Development of durable and fire-tolerant wood-PLA filaments

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University of New Brunswick


Three-dimensional (3D) printing is a rapidly expanding technology. There are many polymer-based filaments used in the 3D printing field, however, growing environmental awareness has increased demand for the development of eco-friendly filaments. In this project, a durable polylactic acid (PLA)/spruce wood composite filament with fire tolerance was developed. Prior to the extrusion of filament, wood flour (WF) was pretreated with polyhexanide hydrochloride (PHMB) and Zinc Oxide (ZnO), then WF was mixed with PLA in two weight percentages (wt.%). Silane coupling agent and Polyethylene-graft-maleic anhydride (MAPE) were further added to improve the interfacial adhesion between the hydrophilic WF and hydrophobic PLA matrix. A total of 12 receipts were developed. Therefore, 12 groups of coupon specimens were made using a 3D printer with 7 replicates for each group. Firstly, the fire tolerance was studied directly using the filaments. Then, the printability of filaments was examined by printing coupon specimens using the 3D printer. Lastly, the properties of coupon specimens were tested, including the modulus of elasticity (MOE), ultimate tensile strength (UTS), water absorption (WA), and thickness swelling (TS). It was found that (1) all the filaments successfully went through the 3D printer, although some fractures and clogs happened; (2) the maximum MOE (1,169 MPa) appeared in group 10, which was almost twice larger than that of group 3 (653 MPa); (2) UTS reached its maximum value (15.046 MPa) in group 1, which was three times higher than that of group 12 (6.102 MPa); (3) WF content was the most influential factor (F = 12.81, P = 0.001 < 0.05), and increasing amount of wood flour decreased MOE and UTS; (4) The maximum TS value (25.13%) was shown in group 12, which was reduced by 72% compared to that of group 1 (6.84%); (5) WA showed the same trend with the minimum value of 0.46% in group 11, 3.13% smaller than the largest value of 3.59% in group 12; (6) The introduction of ZnO did not significantly improve the fire tolerance of filaments, which could be due to the limited amount of ZnO added (2% max in this study). However, the PHMB was discovered showing some potential in improvement of fire tolerance; (7) the SEM results showed that the interfacial adhesion was weak in some areas, suggesting the amount of coupling agents could be increased; and (8) silane coupling agent was found to be a critical factor for the responses according to the ANOVA optimized results.