The use of bamboo charcoal (BC) was investigated as a filler in bambooplastic composites (BPCs) to achieve improved water resistance, physical-mechanical properties, and reduced hydrophilicity. The influence of the BC content and size on the water absorption, contact angle, density, and mechanical properties of bamboo flour/low-density polyethylene (LDPE) composites was tested. Scanning electron microscopy was used to analyse fractured and flat composite surfaces. The results indicated that the BC increased water resistance, achieving optimal results at 8% content. The BC particles that ranged in size from 60 to 100 mesh were more water-resistant than other sized BC. The water contact angle increased with an increase in the BC content or a decrease in the particle size. These results indicated that BC reduced the composite hydrophilicity and that the smaller BC particles improved this effect. The BC strongly connected with the LDPE composites, and the BC contents below 12% improved the flexural properties and increased the density of the BPCs. Also, the impact strength of the BPCs decreased dramatically with a decrease in the BC particle size. These results demonstrated that the integration of BC with BPCs resulted in strengthened water resistance and physical-mechanical properties and reduced hydrophilicity. Bamboo and Rattan and Technology of State Forestry Administration, Beijing, China, 100102; b: Sichuan Agricultural University, Key Laboratory of Wood Industry and Furniture Engineering, Chengdu, China, 611130; * Corresponding author: qindc@icbr.ac.cn Keywords INTRODUCTIONBamboo is an important natural resource that grows faster than trees and is stronger than wood (Jiang 2007). Bamboo-plastic composites (BPCs) are manufactured via hot pressing and extrusion or injection moulding using thermoplastics and bamboo instead of wood (Yeh et al. 2009;Wu et al. 2013). BPCs are widely used in decorations, outdoors, and as non-structural components of buildings (Xian et al. 2015) because they are biodegradable, renewable, and environmentally friendly materials (Zhou et al. 2015a). However, the interface between the polar, hydrophilic bamboo fibres and the non-polar, hydrophobic low-density polyethylene (LDPE) is weak, which leads to the formation of many gaps and pores between the two materials. This incompatibility results in poor mechanical properties and renders the composites vulnerable to water penetration and fungal attack (Hosseinihashemi et al. 2011;Mbarek et al. 2013). Bamboo fibre processing (Li et al. 2013) and coupling agent addition (Tran et al. 2013) are widely used PEER-REVIEWED ARTICLE bioresources.com Chen et al. (2016). "Bamboo/PE composites," BioResources 11(4), 9986-10001. 9987techniques for improving the compatibility of plant fibres and polymers. Another method of eliminating gaps is filler addition, which is a simple and low-cost way to effectively improve the composite morphology and mechanical properties. Nanofillers (Deka and Maji 2012), glass fibres (Zolfaghari et al. 2013), and carb...

The physical-mechanical properties of bamboo-polyethylene composites (BPCs) change depending on the environmental temperature and exposure to moisture during outdoor use. In this study, the water absorption, density, mechanical properties, and wear rate of the composites were tested after immersion in water, and four water temperatures were examined. Bamboo charcoal (BC) was used to improve the properties of the BPCs after hydrothermal aging. The composites were improved because of the strong interfacial interactions between the BC and polymers. The experimental results showed that the water diffusion rate accelerated as the water temperature increased. The BC reduced the water absorption at all of the water temperatures and the diffusion coefficient at temperatures above 39 °C. The wear rate of the composites first increased, and then decreased as the water temperature increased. The density and flexural properties decreased with an increased hydrothermal aging temperature. Overall, hydrothermal aging decreased the water resistance and mechanical properties. Additionally, these effects were enhanced as the water temperature increased, but were countered by the incorporation of the BC.

The cell wall mechanical properties are an important indicator for evaluating the overall mechanical properties of natural bamboo fibers. Using the nanoindentation technique, the variation of the mechanical properties of the fiber cell wall of Bambusa pervariabilis culms with different ages and different positions (both radial and longitudinal) was studied. Moreover, x-ray diffraction (XRD) was employed to measure the microfibril angle (MFA), and the correlation between the MFA and the mechanical properties of the fiber cell wall. The results showed that there was a remarkable difference in the fiber cell wall mechanical properties at different ages and at different radial and longitudinal positions. However, at different ages and at different positions, the absolute value of variation of MFA was less than 1° and was very minor. Furthermore, there was no significant correlation between the fiber cell wall mechanics and MFA, indicating that the mechanical property of the fiber cell walls might be synergistically affected by many factors.

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