Wood particles

There is a hybrid product available which has a veneer back, a layer of PF-coated wood particles, core veneer cross-ply, another layer of wood particles, and a top veneer. This assembly is pressed into a panel, trimmed to size, and sold into the stmctural-use panel market where it competes with plywood and oriented strand board. 

Reconstituted Wood Products. This category includes three general varieties wood flake board, particle board, and wood fiberboard. The manufacturiag processes are similar for all these products except for the size of the wood particles that are glued together. 

After the wood particles are coated with resia, the particles are uniformly distributed iato a board by an air laid process. The art of the process is ia controlling and getting a uniform distribution of the wood particles by blowiag them out onto a collection chain. After forming the board shape it is moved to hot presses where the wood particles are consoHdated and the resia cured. From the hot presses the boards move to trim saws where the boards are cut square to their fiaal size. Ia some cases, the boards are sanded to final thickness and surface smoothness. 

Wood particle and fiber driers are used to dry the raw material for particleboard and similar products (20). Just as with the veneer for plywood, the parhcles must be dried before being mixed with the resins and formed into board. Drying is accomplished in a gas-fired drier, a direct wood-fired drier, or steam coil driers. Many different types of driers are used in the industry. Emissions are fine particles and condensible hydrocarbons, which produce... 

Junge, D. C., and Boubel, R. W., "Analysis of Control Strategies and Compliance Schedules for Wood Particle and Fiber Dryers," EPA Contract Report No. 68-01-3150. PEDCO Environmental Specialists, Cincinnati, 1976. 

Parallam, or laminated strand lumber (LSL) is a beam made by a continuous manufacturing process composed of bigger-size wood needles (very elongated wood particles) reassembled with a structural exterior grade adhesive, the favorite adhesive being isocyanates (pMDI) when heat-curing and PRFs when cold-curing. 

As already indicated above, what one may consider a surface depends on the property under consideration. Adhesion is very much an outer atomic layer issue, unless one is dealing with materials like fibreboard in which the polymer resin may also be involved in mechanical anchoring onto the wood particles. Gloss and other optical properties are related to the penetration depth of optical radiation. The latter depends on the optical properties of the material, but in general involves more than a few micrometer thickness and therewith much more than the outer atomic layers only. It is thus the penetration depth of the probing technique that needs to be suitably selected with respect to the surface problem under investigation. Examples selected for various depths (< 10 nm, 10 s of nm, 100 nm, micrometer scale) have been presented in Chapter 10 of the book by Garton on Infrared Spectroscopy of Polymer Blends, Composites and Surfaces... 

Figure 7.3 Piloted ignition of wood particle board (vertical) by radiant heating [3]...

Figure 8.12 (a) Flame front movement for a wood particle board under opposed flow spread in... 

Tests performed to determine the effectiveness of the CST system for processing shredded wood particles (simulated by sawdust) combined with a carbon-carrier medium encountered several problems, including the following ... 

Research on resin-bonded boards has used wood chips, or fibres, that are acetylated prior to composite manufacture. In almost all cases, acetylation has been achieved by using uncatalysed acetic anhydride. Significant improvements in dimensional stability proportional to the WPG of the wood particles have been reported when acetylated wood is used, and there is also a reduction in irreversible swelling (e.g. Bekere etal., 1978 Arora etal., 1981 Rowell etal., 1986a-e, 1989, 1990, 1991,1995 Yoshida etal., 1986 Youngquist etal., 1986a,b, 1988 Larsson and Tillman, 1989 Subiyanto etal., 1989 Vick etal., 1991 Clemons etal., 1992 Kajita and Imamura, 1993 Sasaki and Kawai,... 

The use of maleic anhydride as a compatiblizer between wood particles and bisphenol A-based polyesters resins has been investigated (Han etal., 1991). In this study, the MA was added directly to the composition of woody matrix filler and resin rather than by pre-modification of the wood. It was found that composite properties were improved by addition of MA, probably due to esterification of the wood occurring during the kneading process. The modification of sawdust using maleic anhydride has been performed in order to provide a compatible filler for polyester resins (Marcovich etal., 1996). Modification was performed at room temperature using a solution of maleic anhydride in acetone, in some cases catalysed with sulphuric acid. It was claimed that bonding occurred under these mild conditions from IR spectroscopic evidence only. 

It has been reported that thermoplastic properties can be imparted to wood by modification of wood particles with fatty acid chlorides in a dinitrogen tetroxide -dimethylformamide - pyridine mixture (Funakoshi etal., 1979 Shiraishi etal, 1979, 1983). A method has also been developed for the modification of wood sawdust without the addition of organic solvents (Thiebaud and Borredon, 1995), and the thermal properties of such modified wood determined (Thiebaud etal, 1997). 

Fenton s reagent chemistry has been used for the direct self-bonding of wood particles. Indirect methods, involving the use of surface-activated fibres in combination with other bonding agents such as furfural and lignosulphonates, have also been studied (Philippou, 1982 Philippou etal, 1982). Since the use of Fenton s reagent requires the presence of... 

The use of enzymatic systems for surface activation of wood particles to form binderless composites has been the subject of study for over 20 years. Enzyme-catalysed bonding of wood can be achieved either by activation of lignin, which is mixed with wood particles, or by surface activation of the wood particles directly (Grdnqvist etal., 2003). 

Imamura, Y., Subiyanto, B., Rowell, R.M. and Nilsson, T. (1989). Dimensional stability and biological resistance of particleboard from acetylated albizzia wood particles. Wood Research Kyoto, 76, 49-58. 

Wood shavings are used in wood particle boards. 

Saastamoinen J.J. and Aho M., Simultaneous Drying and Pyrolysis of Single Wood Particles and Pellets Made of Peaf , presented at the Inti Symposium on Alternative Fuel and Hazardous Wastes, Tulsa, Oklahoma, United States of America,(1984)... 

Simmons W.W. and Ragland W.K., Burning Rate of Millimeter Sized Wood Particles in a Furnace , Combust. Sci. and Tech. 46, 1-15(1986). 

For the hydrolysis operation, it is desirable that the dilute acid be in contact with all parts of the chip, and that the chip be small enough to permit rapid diffusion of the acid into the chips and of the sugar out of the chips. For this operation, the smaller the wood particle the better, because the diffusion is increased as the smaller size of the chips decreases the distance to be traveled. 

The first step when coal or wood particles (we call them chunks or powder and logs or chips, respectively) bum is pyrolysis, in which heat causes the water and volatile organics to evaporate. These gases then bum in oxygen in the boundary layer in the first stage of burning. 

New enological technologies aim to lower volatile acidity, enhance sugar content in must in cool climates and vice versa reduce the alcohol content of wines from hot climates, modify pH, cations, anions and acidity to achieve tartrate stability, complement traditional ageing in oak barrels with the use of small oak wood particles and most recently, extract phenolic compounds by a countercurrent chromatography process from wine to diminish or enrich tannins in red wines. 

Workmanship. The standard of workmanship shall be such as to insure the Droduction of material meeting the requirements of this specification. The DPhA shall be free of extraneous material (such as iron rust, wood particles, dirt, colored salts and other visible impurities). The color of DPhA shall be no... 

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