Chips particleboard

Table II. Versal Tensile Strength of Lignin-Based Adhesive1 Used to Bond Pairs of Wood Laminates and Wood Chips (Particleboard)...

Forest products industries know that temperature increases in piles of sawdust and bark. In pulp and paper mills, self-heating develops in amassed tree chips. Paper rolls stacked hot tend to self-heat, as occasionally do stored bales of waste paper. The wood-base panel products particleboard, hardboard, and fiberboard self-heat after being stacked too hot in the factory. Where in structures the framing lumber, wood-base panels, and lignocellulosic insulation is heated by items such as steam pipes, temperatures tend to rise above that of the heat source. 

Four different methods (vapour-phase acetylation using acetic anhydride, acetylation using ketene gas, liquid phase acetylation using acetic anhydride/xylene, or neat acetic anhydride) were used to acetylate pine wood chips to a variety of WPGs for the production of MUF-bonded particleboards (Nilsson etal., 1988). Composite boards were exposed to unsterile soil in fungal cellar tests. Boards made from ketene acetylated chips were not found to be resistant to decay at the maximum WPG level achieved (17 %) with a liquid acetic anhydride modification, no decay was recorded at a WPG level of c. 18 % after 12 months exposure, whereas with a vapour-phase treatment at the same WPG, evidence for decay was found. 

Kiguchi, M. and Suzuki, M. (1985). Physical properties of particleboard with acetylated chips and binder. Mokuzai Gakkaishi, 31(3), 200-208. 

Kiguchi, M. and Yamamoto, K. (1991). Dimensional stability and decay resistance of hot-melt self bonded particleboard by surface benzylated pine chips. International Research Group on Wood Preservation, Doc. No. IRGAVP 3652. 

Rowell, R.M., Simonson, R. and Tilhnan, A.-M. (1986a). A simplified procedure for the acetylation of chips for dimensionally stabilized particleboard products. Paperi ia Puu, 68(10), 740-744. 

Particleboard (waste wood chips or dust plus a resin) panelling, subflooring, general plywood and lumber replacement Paper-base laminates (plies of wood plus a phenolic, urea, or melamine resin) structural and machine parts... 

Phenolic resins produced by the reaction of phenol and formaldehyde were used as adhesives by Leo Baekeland in the early 1900 s. This inexpensive resin is still used for binding thin sheets of wood to produce plywood. Urea resins produced by the reactions of urea and formaldehyde have been used since 1930 as binders for wood chips in particleboard. 

Particle Preparation. The initial step in particleboard production is reduction of the wood raw material into the desired configuration for the particular particleboard to be manufactured. The wood may be received from a number of sources and in a variety of forms. Roundwood, chips, planer shavings, plywood trim, and sawdust are the most common raw material forms and rarely does one particleboard plant use more than two or three of the above sources. Different processing steps are required to produce quality particles from each of the above sources consequently, each plant is limited to the source which is compatible with their... 

Chippers and flakers are the most widely used knife reduction systems. Chippers produce coarse particles from roundwood, slabs, plywood trim, and other residues from the primary wood industry. Chippers are the initial reduction step in particle preparation and further size reduction is necessary to produce a satisfactory particle. The chipping operation may be located at the particleboard plant or the chips may be delivered to the plant from an in-woods chipping operation, a chip-n-saw mill, or from another primary wood industry. Screening after the chipper removes all fines and oversize chips before they enter the secondary reduction step. Oversize chips are recycled to the chipper and fines are normally sent to the boiler for fuel. 

One of today s fastest growing segments of the wood composition board industry is production of medium density fiberboard (MDF) using a dry process similar to that used for particleboard. First mention of the possibility of utilizing bark for MDF came in a presentation by Brooks in 1971 (43). He described a process in which a homogenous board with superior properties could be made from such raw materials as mixed, unbarked hardwood pulp chips unbarked pine chips, if bark content was less than 30% forest thinnings, branches, and so on and hardwood bark. Furnish was prepared by double-disk pressurized refiners. Brooks concluded a plant could be built to operate on 100% hardwood bark. 

All dry veneer waste and plywood trim waste not used for fuel is commonly chipped and sold to particleboard plants as furnish. 

Our houses are built of wood (cellulose and lignin), sheathed with particleboard (wood chips pressed with plastic resin), wrapped with plastic sheeting, clad with siding (vinyl), and decorated with plastic shutters. Buildings with wood siding are covered with paint. Inside, water flows through plastic pipes, the floors are covered with tiles (vinyl) or carpeting (polyester, nylon), the walls are covered with wallpaper (vinyl) or painted (acrylics), and the... 

The mixed wood and bark residues burned directly are collectively termed hog fuel. Over the past decade, there has been a trend to channel more and more of the cleaner, drier, and larger-sized mill residues into raw materials for products. The coarse wood residues (slabs, trim, edgings, etc.) are chipped and sent to pulp mills. Also, considerable sawdust now is being pulped instead of being burned for fuel. Some of the residues, including shavings, also are used for particleboard. This means that hog fuel contains the less desirable, dirtier, and wetter forms of waste. 

One-layer particleboards were prepared from Eucalyptus chips with a resin content of 10 percent on dry chips. The boards were formed 12-mm thick on a laboratory press with the press platens at 170 °C for press times of 15 minutes. 

Table IV. Internal Bond Strength of Particleboard, 12-mm-Thick, Prepared from Soda Bagasse Lignin Adhesives (10% on Dry Chips) After Pressing at 170 °C for 15 Minutes...

The moisture dependence of the two PF-extended lignin adhesives was subsequently determined. Single-layer boards were prepared with the resinated chips at different moisture contents. The adhesive content (10%) and press conditions (170 °C, 15 min.) were kept constant. The results presented in Figure 4 indicate the deleterious effect of high moisture contents of the chips on the strength of the boards. The application of the lignin particleboard adhesive thus clearly requires strict control of the moisture content of the chips. 

Figure 5. Strength of three-layer particleboard (20% surface chips) glued with hydroxymethylated bagasse lignin/commercial PF resin (67 33) and pressed at 170 to 180 °C for different times, 12% chip moisture content, final density 680 kg/m3.

Recently, particleboards have been prepared from mixtures of acetylated and untreated wood chips [55]. Thickness swelling and water absorption after soaking in water for 24 h decrease as the number of acetylated chips increases. The specimens containing 100% of acetylated chips show no sign of decay. Further, particleboards from acetylated wood particles have been reported to have higher mechanical properties than those from PO-treated particles [56]. 

Particleboard or mat-formed composite board is one of the products that can use recycled wood as a raw material. According to questionnaires, recycled wood used in the particleboard industry is estimated to be 20% of the total chips, and the amounts have been increasing. Laboratory scale particleboards were made using recycled P-chip and S-chip to evaluate chip quality. The results showed that the quality of P-chip was equal to that of ordinary chip. Hammer-milled particle from low grade chips can be used as a core material of particleboard. A new type of structural board with three-layer construction was proposed to expand the use of recycled wood chips. 

Chip makers dealing with waste wood produced about 1.8 million tons per year, and about 70 % of chips were for fuel and about 30% were recycled as a raw material in the paper and board industries (4). The amount of reuse of waste wood was very small compared with the generation. Particleboard or mat-formed board is a product that can use recycled wood (5) (6). Thus, the problems of recycled wood for board making was discussed in this paper. 

In this section, properties of particleboard made from demolition wood were evaluated using P-chip and S-chip in laboratory scale tests. 

Demolition wood chips with some contamination or deterioration can be used as core material of particleboard. 

Particleboard utilizes residue materials from other wood processing operations. Sawdust and shavings predominate, although most plants are able to use chips or flakes made from roundwood to meet specific strength requirements in the product. Cost is the major driver, with the proportion of high cost material such as chips or roundwood limited to that necessary to meet product requirements. Particle size distribution and shape have become more important as the effect of these variables on product quality has been recognised, leading to reductions in cost. 

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