Wood particle size

Circumventing the lignin barrier to enzymatic digestion of the polysaccharides occurs when wood is finely ground. Below a certain wood particle size, the polysaccharides (celluloses and hemicellu-... 

Stndying microbial degradation of 50% WPCs by brown-rot and white-rot fungi (G. trabeum and T. versicolor, respectively), it was found that the decay was more prononnced as the wood particle size increased [9]. The authors found that decay in the pine-based composites was more sensitive to particle size than that in the maple-based composites. It is noticeable from the above examples that for the same soil block test, ASTM 1413 or similar to it, the weight loss figures are quite different, and vary from fractions of a percent to qnite high numbers. Indeed, as it was shown, extended composite material samples are mnch more sensitive to soil block test compared to compression-molded and injection-molded sample. After 12 weeks,... 

S.A. Verhey and P.E. Laks, Wood particle size affects the decay resistance of woodfiber/ thermoplastic composites. Forest Prod. J., 2002, 52, 78-81. 

A variety of wood particle sizes are used to produce WPCs depending on the type of product. The dimensions of wood particles are usually measured in mesh size as the particles resulting from passing through a mesh with a given number of mesh squares in a square inch. The wood used in WPCs is most often in particulate form (wood flour) or very short fibers rather than longer individual fibers. Commonly, mesh sizes 20, 40, 60, and 80 are used in WPC production. 

Wood Particle Size and Wood/Plastic Ratios... 

Mankowski and Morrell [10] examined the influence of the wood/plastic ratio and wood particle size on the decay of commercial WPCs made with pine and HOPE. A 20% wood weight loss was observed in the WPCs made with 70% wood (small wood particles) after exposure to a brown-rot fungus. In contrast, little or no degradation was observed in two samples of WPCs made with 50% wood content, despite the use of larger wood particles. These results suggest that the amount rather than size of the wood particles may have a greater effect on WPC durability [13, 22],... 

The particle size also has an effect on the property performance of WPG products. For increasing wood particle size in PP-based WPG products, both melt index and tensile elongation increase, notched impact energy increases but unnotched impact energy decreases, and flexural modulus and strength increase for particles smaller than 0.25 mm. 

B. Wood Particle Size and Shape Before Pressing... 

B. C. Wood, Particle Sizing pp. 83-89 in Engineered Materials Handbook, Vol. 4, Ceramics and Glasses. Edited by S.J. Schneider. ASM International, Newbury, OH, 1991. 

The ideal resin distribution for a particleboard manufacturer is usually defined by the maximum board properties obtainable when using a given minimal amount of adhesive. The cost of a continuous film of adhesive becomes prohibitive as wood particle size decreases in a composite because of the enormous wood surface area involved. How to obtain and measure the ideal resin distribution is subject to debate. Wood particle geometry, amount of adhesive applied, adhesive application method, spray... 

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. 

Specific gravity is direcdy related to the bulk density of waste fuels prepared ia a variety of ways. Solid oven-dry (OD) wood, for example, has a typical bulk density of 48.1 kg/m (301b/ft ). In coarse hogged form, eg, <1.9-cm minor dimension, this bulk density declines to about24kg/m (151b/ft ). In pulverized form, at a particle size <0.16 cm, this bulk density declines to 16—19 kg/m (10—12 Ib/ft ). Similar relationships hold for municipal waste, agricultural wastes, and related fuels. 

Fiber Slurry Pipelines. Pipelines to carry suspensions of wood, paper, sludge, etc, have found commercial acceptance. Most of them are less than 15 km long but have diameters of up to 500 mm. These slurries are often concentrated and display viscous plastic properties, although particle sizes may vary special pumps are used. One such hydrotransport system carries a cellulose slurry by pipeline from the plant to a paper plant near Heidenau, Germany. The 250-mm dia pipeline carries 60 t/d over the 3-km distance to thickeners. In Sweden, a 3.7-km, 500-mm dia pipeline moves cellulose by... 

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. 

N.G. Stanley-Wood and R.W. Lines. Particle Size Analysis. Roy. Soc. Chem. Special Publication 102 (1992) TA 418.8 P32. 

Leaves, flowers, herbs - coarsely to moderately finely chopped (particle size ca. 4 mm) Woods, barks, and roots finely chopped to coarsely powdered (particle size ca, 2.5 mm) Fruits and seeds crushed or coarsely powdered immediately before use (particle size ca. 2 mm) ... 

Stanley-Wood, N. G., and Lines, R. W. (eds ), "Particle Size Analysis." Royal Society of Chemistry, Cambridge, UK, 1992. 

Traditionally, active carbons are made in particulate form, either as powders (particle size < 100 pm, with an average diameter of -20 pm) or granules (particle size in the range 100 pm to several mm). The main precursor materials for particulate active carbons, PAC, are wood, coal, lignite, nutshells especially from coconuts, and peat. In 1985, 360 kt of such precursors (including 36 % wood and 28 % coal) were used to make active carbons [10], of which nearly 80 % were used in liquid-phase applications, with the rest being used in gas-phase applications. Important factors in the selection of a precursor material for an active carbon include availability and cost, carbon yield and inorganic (mainly mineral) matter content, and ease of activation. 

In chemical activation processes, the precursor is first treated with a chemical activation agent, often phosphoric acid, and then heated to a temperature of 450 -700 °C in an activation kiln. The char is then washed with water to remove the acid from the carbon. The filtrate is passed to a chemical recovery unit for recycling. The carbon is dried, and the product is often screened to obtain a specific particle size range. A diagram of a process for the chemical activation of a wood precursor is shown in Fig. 3. 

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. 

Perlite and Solka-floc are finely divided powders manufactured from a volcanic mineral and from wood pulp respectively, which have filtration properties very similar to those of diatomite. Like diatomite, they are inert to a wide range of process liquids. Like diatomite, they are available in a range of particle-size distributions to give the desired clarity and flowrate in different applications. On a cost-of-use basis, they are as economical as, or more economical than, diatomite. 

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