Abstract
Additive manufacturing or 3D printing has the potential to displace some of the current manufacturing techniques and is particularly attractive if local renewable waste resources can be used. In this study, rice husk, and wood powders were compounded in polylactic acid (PLA) by twin screw extrusion to produce filaments for fused-deposition modeling 3D printing. The biomasses were characterized in terms of physical features (e.g., particle size, density) and chemical compositions (e.g., solid state nuclear magnetic resonance, ash content). The two biomasses were found to have a different impact on the rheological behavior of the compounds and the extrusion process overall stability. When comparing the complex viscosity of neat PLA to the biomass/PLA compounds, the integration of wood powder increased the complex viscosity of the compound, whereas the integration of rice husk powder decreased it. This significant difference in rheological behavior was attributed to the higher specific surface area (and chemical reactivity) of the rice husk particles and the presence of silica in rice husks compared to the wood powder. Color variations were also observed. Despite the biomass filler and rheological behavior differences, the mechanical properties of the 3D printed samples were similar and predominantly affected by the printing direction.
Highlights
The popularity of incorporating lignocellulosic biomasses in thermoplastic polymers has increased significantly due to their sustainability advantage, low density, thermal, and noise insulation capacity and stiffening performances (Le Guen and Newman, 2007; Müssig, 2010; Gallos et al, 2017; Lammi et al, 2018)
Rice husk powder contains a considerable proportion of fine particles below 20 μm whereas wood powder has a high content of coarse particle as observed in the shape of the particle size distribution graph (Figure 1)
Process Stability and Thinning Behavior. Whilst both biomass fillers caused a reduction in the polylactic acid (PLA) molecular chain length, the extrusion process was more unstable during rice husk powder compounding
Summary
The popularity of incorporating lignocellulosic biomasses in thermoplastic polymers has increased significantly due to their sustainability advantage, low density, thermal, and noise insulation capacity and stiffening performances (Le Guen and Newman, 2007; Müssig, 2010; Gallos et al, 2017; Lammi et al, 2018). Amongst the lignocellulosic feedstocks available, rice husk is of particular interest due to its current abundancy (i.e., estimated between 128 and 148 million tons of unutilized waste) (Giddel and Jivan, 2007; Pode, 2016), and chemical make-up. It is composed of around 80–85 wt.% lignocellulosic materials (e.g., cellulose, hemicellulose, lignin), 15–20 wt.% of amorphous silica and 1.1 to 2.5 wt.% of proteins (Juliano et al, 1987; Vadiveloo et al, 2009; Ummah et al, 2015). The incorporation of nanosilica in polylactic acid (PLA) was reported to improve the thermal stability and mechanical properties of composites (Lv et al, 2016)
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