PAPERmaking! g FROM THE PUBLISHERS OF PAPER TECHNOLOGY Volume 2, Number 1, 2016
INTRODUCTION Particleboard is a wood-based composite consisting of various shapes and sizes of lignocellulosic particles bonded with an adhesive and consolidated under heat and pressure. Particleboard makes up about 57% of total consumption of wood-based panels consumed, and demand is continuously growing, at 2% to 5% annually. Uses include housing construction, furniture manufacturing, and interior decoration of wall and ceiling panelling (Drake 1997). The main source of fibre material for the particleboard and furniture industries in Malaysia is rubberwood, which is estimated to be 2,000,000m 3 annually, leading to a shortage of rubberwood (Anonymous 2009). Wood normally takes a long time to grow to useable sizes, and processing wood as a material is difficult. Thus, it is essential to find alternatives for wood, as the raw wood supply has diminished because of deforestation and forest degradation activities, along with high demand for wood-based panels (Ashori and Nourbakhsh 2008). Research has been carried out on a wide variety of non-wood plant fibres and agricultural residues, such as bagasse, coconut husks, bamboo, and a few more cheap raw materials from many different regions of the world, all of which may serve as a replacement for conventional woods (Miki et al. 2003). Currently, most commercial particleboard is bonded using formaldehyde-based adhesives made from non-renewable sources. Urea formaldehyde is the most common resin used because of its fast curing time, clear colour, and low cost compared with other synthetic resins (Hashim et al. 2012). Nonetheless, formaldehyde emissions from urea formaldehyde-bonded panels have been subjected to strict legislation and gained attention as a public health concern in the last 30 years. The 10% usage of urea formaldehyde resin from the total dry weight of particleboard makes up about 60% of the overall cost of particleboard production. Also, synthetic adhesives may have effects on human health, such as cancer and irritation of the eyes, nose, and throat, and may lead to environmental pollution (Okuda and Sato 2004). The manufacturing of binderless board by utilising lignin present in the lignocellulosic fibre raw material is a good substitution solution for expensive synthetic resin used in current particleboards. Because there is no synthetic adhesive used, it is possible that no curing period is needed, and it is economical. Lignin is a complex phenolic amorphous polymer that plays roles in cell wall development and serves to bond individual cells in plants. Lignin has been reported to play an important role in self-bonding boards, acting as a natural binder for fibres (Okuda and Sato 2004). When heat is applied to the fibres, lignin melts to the surface of fibres, and as pressure is applied to the fibres, lignin binds the fibres together. Previous studies have reported that the glass transition values in a dry state for lignin, cellulose, and hemicelluloses were 200, 220, and 170°C, respectively (Hashim et al. 2011). Research on binderless boards has attracted interest because of its excellent physical and mechanical properties, environmental friendliness, and renewable sources, and because it is both recyclable and economical. It is highly trusted as a competitive wood supplement in the wood-based industry, as the manufacturing processes for binderless boards are simple; it is hoped that it can be easily applied to commercial production (Panyakaew and Fotios 2011). Binderless boards are still in the research stage. This has left room for development since their introduction in the early 1980s (Baskaran et al. 2012). There have been various materials used in manufacturing binderless boards, such as kenaf (Okuda and Sato 2004, 2006; Widyorini et al. 2005a; Xu et al. 2006; Aisyah et al. 2013), oil palm (Suzuki et al. 1998; Hashim et al. 2010, 2011a,b, 2012; Baskaran et al. 2012), date palm (Saadaoui et al. 2013), bamboo (Bahari et al. 2008), coconut husk (van Dam et al.
Page 2 of 18
Article 4 – Wood Panels
Made with FlippingBook Digital Publishing Software