Development of durable composite filaments for 3D printing

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University of New Brunswick


The 3-dimensional (3D) printing technology has been recently successfully applied to all aspects of life such as architecture and education. The filaments for 3D printing are usually made from pure plastics and inorganic fibers, causing some shortcomings to the printed products, such as insufficient strength and environmental issues. The use of biofibers has become a new trend. This thesis report was aimed to develop an optimized recipe of making durable filaments using spruce wood flour, polylactic acid (PLA) and polyhexanide hydrochloride (PHMB), and silane. These materials were melt-blended and extruded into wood-plastic filaments using a twin screw extruder, which were, thereafter, used to print the coupon specimens via a 3d printer. Tension, water absorption and swelling and antimicrobial tests were conducted. The scanning electron microscopy (SEM) was carried out to investigate the interfacial bonding of the filaments made. It was found that (1) all the filaments successfully went through the 3D printer, suggesting the printability of the filament was promising; (2) the ultimate tensile strength (UTS) and modulus of elasticity (MOE) of the specimens were, after adding wood flour, increased by 68.28% and 73.08%, respectively; (3) the addition of silane created the weak interfacial layer, reducing UTS and MOE by 59.19% and 62.25%, respectively; (4) adding 5% wood flour increased the 2-hour and 24-hour water absorption by about 60% and 175%, respectively, and the swelling in diameter was increased by 6.62% after 24 hours immersion; (5) antimicrobial property was significantly improved with the addition of 2% PHMB, with the growth inhibition rate being 99.95%; and (6) the SEM showed that the interfacial adhesion was weak in some areas, therefore, the fracture surface is erratic. It could be recommended that the filaments developed in this study could be used in food industry. Key words: 3D printing, antimicrobial wood-plastic filament, fracture morphology, interfacial bonding, modulus of elasticity, polyhexanide hydrochloride, polylactic acid, spruce, ultimate tensile strength, water absorption.