Abstract
In this study, four kinds of lignocellulosic fibers (LFs), namely, those from Chinese fir (Cunninghamia lanceolata), Taiwan red pine (Pinus taiwanensis), India-charcoal trema (Trema orientalis) and makino bamboo (Phyllostachys makinoi), were selected as reinforcements and incorporated into high-density polyethylene (HDPE) to manufacture wood-plastic composites (WPCs) by a flat platen pressing process. In addition to comparing the differences in the physico-mechanical properties of these composites, their chemical compositions were evaluated and their thermal decomposition kinetics were analyzed to investigate the effects of the lignocellulosic species on the properties of the WPCs. The results showed that the WPC made with Chinese fir displayed a typical M-shaped vertical density profile due to the high aspect ratio of its LFs, while a flat vertical density profile was observed for the WPCs made with other LFs. Thus, the WPC made with Chinese fir exhibited higher flexural properties and lower internal bond strength (IB) than other WPCs. In addition, the Taiwan red pine contained the lowest holocellulose content and the highest extractives and α-cellulose contents, which gave the resulting WPC lower water absorption and flexural properties. On the other hand, consistent with the flexural properties, the results of thermal decomposition kinetic analysis showed that the activation energy of the LFs at 10% of the conversion rate increased in the order of Taiwan red pine (146–161 kJ/mol), makino bamboo (158–175 kJ/mol), India-charcoal trema (185–194 kJ/mol) and Chinese fir (194–202 kJ/mol). These results indicate that the morphology, chemical composition and thermal stability of the LFs can have a substantial impact on the physico-mechanical properties of the resulting WPCs.
Highlights
Wood is an anisotropic material and is susceptible to deformation, warping and cracking due to dimensional instability from changes in ambient humidity
When a wood-plastic composites (WPCs) is made with Chinese fir, which has fibers with a larger aspect ratio
MOR and modulus of elasticity (MOE) values, but it has higher water absorption and thickness swelling after 24 h of soaking
Summary
Wood is an anisotropic material and is susceptible to deformation, warping and cracking due to dimensional instability from changes in ambient humidity. Polymers 2017, 9, 726 and the construction industry These WPCs can serve as alternatives to solid wood for various fixtures, such as window frames, fencing, roofing, decking and siding [5]. Little information is available on the effect of various lignocellulosic fibers (LFs) on the properties of WPC. An objective of the current study was to investigate the effects of the morphology and chemical composition of the lignocellulosic materials on the physico-mechanical properties of the WPCs. Three common fast-growing plantation species and one common economical and popular bamboo species in Taiwan, Chinese fir (Cunninghamia lanceolata), Taiwan red pine (Pinus taiwanensis), India-charcoal trema (Trema orientalis) and makino bamboo (Phyllostachys makinoi), were used as reinforcements or fillers to prepare WPCs in this study. The thermal decomposition kinetics of these lignocellulosic materials were evaluated using thermogravimetric analysis (TGA) by various isoconversional methods
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