DOI 10.1515/polyeng-2013-0168 J Polym Eng 2014; 34(2): 141–144
Chaowei Pang*, Robert Shanks and Fugen Daver
Cellulose fibre-cellulose acetate hybrid composites with nanosilica Abstract: Biocomposites incorporating cellulose fibres, a renewable resource, have high modulus and strength and flexibility suitable for structural applications. Solution casting, ultrasonication, and compression moulding methods were used to prepare the specimens. Results show that plasticiser indeed improved the flexibility of the composite and adding fillers further enhanced the performance of the composite. Keywords: biocomposite; cellulose; kenaf; morphology; nanocomposite. *Corresponding author: Chaowei Pang, School of Aerospace, Mechanical, and Manufacturing Engineering, RMIT University, Building 251 Cnr. Plenty Road and McKimmies Lane, Bundoora, Victoria 3083, Australia; and School of Applied Sciences, RMIT University, GPO Box 2476, Melbourne, Victoria 3001, Australia, e-mail:
[email protected] Robert Shanks: School of Applied Sciences, RMIT University, GPO Box 2476, Melbourne, Victoria 3001, Australia Fugen Daver: School of Aerospace, Mechanical, and Manufacturing Engineering, RMIT University, Building 251 Cnr. Plenty Road and McKimmies Lane, Bundoora, Victoria 3083, Australia
1 Introduction Composites are common materials for applications in an extensive range of products. Plastics extracted from petroleum take from 1 to 10 years to degrade (aerobically forming carbon dioxide). In addition, the process of biomass turning to petroleum takes 1 million years. Therefore, there is a crucial need for not only biodegradable but also sustainable plastics [1]. Recent developments in use of natural fibres in composites were introduced with the intention of yielding lighter composites [2, 3]. Biocomposite is an area of research that is developing owing to its positive environmental impact [1]. In particular, cellulose fibres, obtained from plants, have high strength and modulus suited for composite structures for various applications. The aim is to prepare cellulose acetate reinforced with kenaf fibre composites that have high modulus, strength, and flexibility, with the introduction of nanoparticles.
There are three categories of natural fibres: bast, seed or fruit, and leaf. For this study, kenaf, which is a bast fibre, is used. Kenaf, Hibiscus cannabinus, is a fast-growing tropical crop. It is harvested within 3–5 months after sowing, and yields about 18,000 kg/ha. Kenaf fibres have been used in various applications such as ceiling panels, fencing, and outdoor furniture [3, 4]. There are several farming advantages, including minimal fertilizers, pesticides, and water required because it is a woody plant. In comparison, pine trees are thinned after 15 years and harvested after 32 years for various products [5]. It also has a low density and high specific mechanical properties [6]. There are other factors that promote the cultivation of kenaf, including the growth of the plant and processing of fibres. First, it has the ability to absorb phosphorus and nitrogen in soil and/or wasted water. It accumulates carbon dioxide at a high rate [7]. The cultivation of kenaf has grown owing to its abilities to absorb phosphorus and nitrogen in soil [6] and accumulate carbon dioxide at a high rate [7]. This is due to its higher photosynthesis rate compared with conventional trees [6]. The processing of kenaf fibres is non-abrasive. The energy consumption in the production of kenaf fibres (15 MJ/kg) is much lower compared with the production of glass fibres (54 MJ/ kg) [6]. One of the few issues in using natural fibre is moisture absorption, due to its hydrophilic nature. One of the common methods to reduce moisture absorption is mercerisation or alkalisation [8]. Mercerisation “reduces the hydrogen bonding capacity of the cellulose, eliminating open hydroxyl groups that tend to bond with water molecule” [8]. In addition, this surface treatment dissolves hemicellulose, the most hydrophilic component in natural fibre, thus minimizing moisture absorption in natural fibres. As the fibre surface is mercerised, reducing moisture absorption, it also improves the mechanical properties of the fibre [7, 8]. Cellulose is one of the many polymers found in nature. It is a structural component of plant cell walls and exists as microfibrils of 2–20 nm in diameter and 0.1–40 µm. Cellulose does not dissolve in common solvents. Therefore, cellulose acetate was used in this study. It is a derivative of cellulose, with acetic anhydride in acetic acid solvent. Cellulose acetate, unlike cellulose, is soluble in common solvents, such as dichloromethane and methanol [9].
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