Vol: 1 Issue: 1
UREA -FORMALDEHYDE FREE PARTICLEBOARDS FROM WOOD WASTES USING GLUTARALDEHYDE MODIFIED CASSAVA STARCH AS BINDER
Atowon, A. D., Ita. E.O, Ushie, EO
1. INTRODUCTION
Wood wastes are wood fragments and particle from industrial or saw milling processing industries, forest harvesting, construction and demolition activities. Huge quantities of the post- consumer wood waste are generated in a significant rate and the method and level of recycling is inadequate compared to other construction and demolition wastes. Several, reports showed that between 8 and 50% of the entire wood-based material being used yearly for various end uses application become wastes. Wood wastes consist of; solid timber, timber shavings, sawdust, off-cut, veneer panels and combination of two or more of them. Hence, 10% of solid wastes are associated from demolition and construction site, these wastes are majorly dumped in landfills and burnt in combustion chamber, this opposing hazard to the environment, wood waste could be reused by sorting, recycle and utilized as raw material for the development of values added products (particle board and fiber board); those could be utilized as ceiling board, walls, flooring, furniture etc [1][2][3][4]. However, recycling of wood waste with formaldehyde- based resin will generate high leaching of emissions from the virgin product to the environment than expected dose, basically, those will be in two sources, first the breaking down of the formaldehyde in the parent product, secondly formation of the new formaldehyde adhesive utilized for the new products [5][3]. The leaching of formaldehyde will alter the air quality of indoor facilities made from the second-generation products and imposed serious health challenges for the occupants more than older structure. This health problem, however, showed the important role of formaldehyde inducting illness through immune mechanism and toxicity. Hence, to curbed these problems various study has showed approaches to minimized the formaldehyde emission from engineered wood-based products, through chemical modification with natural resins [6][7][8]. Second method involves the utilization of formaldehyde free adhesives, these are vegetable based, which are environmentally clean and friendly, green and could be utilized for engineered wood products without health issues. Natural latex, oxidase, gum Arabic, corn starch, soy-based adhesive, wheat gluten, and nano- modified starch [9][10]. Amongst others, cassava is one of higher source of starch of natural polymers of low cost and largely variable. The processing of cassava to cassava flake and other end- products of cassava generate commercial quantities of the natural polymer for industrial uses [11][10] . Study showed that, cassava starch contained amylose and amylopectin, amylopectin is a polymer of several D-glucose molecules.80% of amylopectin is present in starch, amylopectin molecules are linked by α-1,4-glycosidic bonds and α-1,6-glycoside bonds. It is a water insoluble fraction. Amylose is a polysaccharide made of α-D-glucose units, bonded to each other through α(1→4) glycosidic bonds. It is one of the two components of starch making up approximately 20-30%. Fig 1 showed the chemical structure of amylose and amylopectin. Nigeria is largest producer of cassava in Africa, contributing 30%, it’s a source of food in Nigerian and less application industrial end products, compared to Asia, which has been major raw material for various end product without affect food value chain of the Asia ecosystems [12][13][11]. Studies showed that, cassava thrive in poor fertile soil unlike other sources of starch like yam etc. Resins in wood -based industries has necessitated the utilization of starch based, but, the main drawbacks of bonded boards are the poor dimensional stability and low bonding properties which are associated in cases involving starch as adhesive [14][15][16][9][17]. The hygroscopicity of cassava-based starch in engineered wood based has gears the current study. Nevertheless, some treatments have been used in some studies to improve the bonding capacity of starch as a doable resin in various wood end uses applications [15][10][11]. Studies, showed chemical modification of starch with low percent of Urea formaldehyde as binder, the mechanical properties of the board indicated higher value in MOR, thickness swelling and density were observed in test sample with modified binder in comparison with unmodified[11] Similarly, study by[18] developed composite material of difference sieved sizes, using wood waste, bonded with chemically modified starch, results showed that, MOR and internal bonding of panels aligned with ASTM Standards. Modifications of starch as constituent in formaldehyde adhesive is to input some functional groups to modified it role in end uses applications. The chemical modifications are basically grafting copolymerization, crosslink reactions. Few studies exist on the utilization of cassava starch obtained from residue of cassava processing and its subsequent modification, being utilized with wood waste from saw milling, demolition and construction site for particle board production. However, the aim of the study is to bridge dearth of knowledge gap in the utilization of cassava modified starch in the production of engineered wood products for sustainable ecosystem.
2. Material and methods
2.1 Material preparation
Wood wastes were sourced from a local saw mill in calabar, wood chips were from different species of timber material, sorted from metals and debris, the wood chip waste (WC) were firstly air dried and further oven dried at 800C until reading on the moisture analyzer were ±5% Moisture content (MC), the wood meal were then sieved and packaged into two sieved sizes of 600μm and 0.08mm respectively. The cassava starch (CS) was sourced locally in a cassava.