Wood, composition

The following Hst includes most of the adhesives which can be or have been used in wood and wood composite bonding appHcations. 

Economic Aspects. In 1994 there were 8 operational insulation board producers in the United States. These mills produced about 1.15 X 10 m (2). The number of mills and total production volume have also decreased in this industry, primarily as a result of changes in building codes and avadabihty of other competitive sheathing products. Both wood composite panels and plastic foam sheathings have captured a segment of these markets. 

Miscellaneous. In ore flotation, sodium sulfite functions as a selective depressant. In textile processing, sodium sulfite is used as a bleach for wood (qv) and polyamide fibers and as an antichlor after the use of chlorine bleach. Synthetic appHcations of sodium sulfite include production of sodium thiosulfite by addition of sulfur and the introduction of sulfonate groups into dyestuffs and other organic products. Sodium sulfite is useful as a scavenger for formaldehyde in aminoplast—wood compositions, and as a buffer in chrome tanning of leather. 

J. Bodig and B. A. Jayne, Mechanics of Wood and Wood Composites, Van Nostrand Reinhold, 1982. 

Medium-density fiberboard (MDF) a flat pressed wood composite panel composed of randomly oriented wood fibers obtained by thermomechanical wood pulping and bonded by hot-pre.ssing by using thermosetting adhesive resins. The panel has generally a density of approximately 850 kg/m- and the average amount of resin solids in the board core section is between 11 % and 14% on dry wood. 

Kharazipour, A., Hiitterman, A., Biotechnological production of wood composites. In Bruce, A. and Palfreyman, J.W. (Eds.), Forest Products Biotechnology, Ch. 9. Taylor and Francis, London, 1998, pp. 141-150. 

Industrial finishing systems are applied to a wide variety of substrates, the majority of which are metallic, but they are also applied to paper, wood, wood composites, cement products and plastics. Often a high quality of decoration is required, as well as protection from a number of hazards, such as knocks, abrasions, bending or forming and contact with non-corrosive liquids. Resistance to the weather may be required. Outdoor finishing systems, and many others, are also required to protect metal against corrosion. 

Kharazipour, A., Hiittermann, A. and Luedemann, H.D. (1997). Enzymatic activation of wood fibres as a means of the production of wood composites. Journal of Adhesion Science and Technology, 11(3), 419-4 27. 

Li, J.Z., Euruno, T. and Katoh, S. (2000a). Dimensional stability and flame resistance of silicate-acetylated and propionylated wood composites. Journal of Wood Chemistry and Technology, 20(4), 441 53. 

Timar, M.C., Mihai, M.D. and Baciu, G. (1997a). About the water and biological resistance of some new chemically modified wood composites. International Research Group on Wood Preservation, Doc. No. IRG/WP 97-40077. 

Timar, M.C., Maher, K., Irle, M. and Mihai, M.D. (2004). Thermal forming of chemically modified wood to make high performance plastic-hke wood composites. Holzforschung, 58(5), 519-528. 

More recently, about ten years ago, the first wood composite was marketed in pellets. 

Currently marketed wood composites are based on 30% to 70% natural-fibre-filled polypropylene, polyethylene, polystyrene and PVC. Formulations have high performances and are more expensive than the virgin material. 

The US natural fibre and wood composite market was estimated in Plastics Additives ... 

Traditional processes can be modified to better industrialize the manufacturing of medium- or short-run manufacturing. In the thermoplastic composite field, the Pressure Diaphorm Process allows the processing of continuous fibre reinforced thermoplastics with low pressures. The press and the moulds (wood, composite or aluminium) can be about 70% cheaper. The process is convenient for short and medium runs in the range of 1000 up to 100000 parts. 

Hemicellulose constitute 20-30% of the total wood composition on dry basis. Hemicellulose is a polysaccharide, like cellulose. 

The principle uses of the zinc borate Zn[B304(0H)3] are as a polymer additive and preservative for wood composites, such as oriented strand board (OSB). As a polymer additive it functions as a fire retardant synergist and modifier of electrical and optical properties. Its function as a fire retardant additive is discussed further below. A substantial amount of Zn[B304(0H)3] is used to improve the tracking index, which is an important performance criterion for polymers, such as polyamides (nylon) and polybutyl teraphtha-lates (PBT), used in electrical applications. 

Wood and wood composites Solid wood as well as particleboard and medium-density fiberboard (MDF) are suitable substrates for powder coating. They tend to emit volatiles such as entrapped air and moisture, and therefore require curing temperatures below 100°C (212°F) and preferably nof higher than 80°C (144°F). A typical curing procedure for MDF is in Table 7.8. 

Dual-cure resins for wood composites. These resins (heat and EB irradiation systems) are based on urethane-acrylate thermoplastic adhesive demonstrate efficacy to bond wood. Eow amounfs of EB radiation were needed to produce a wood bond that survived shipping and that improved the composite modulus. The system demonstrated promise and a new direction for wood adhesives. 

The objective of this work was to demonstrate the utility of organosolv red oak lignin (a projected cheaper polyphenol than phenol) in phenolic adhesives for wood composites. This work involved three stages ... 

Sellers, T., Jr. Wooten, A. L. Cook, P. M. Proc. Structural Wood Composites New Technologies for Expanding Markets Forest Products Research Society, Madison, WI, 1988, Proc. No. 47359, 43-50. 

Composites Both UV and EB cures are employed for the production of wood composite materials and in fiber-reinforced composites for aircraft and aerospace applications. The EB technology has been successful in the manufacture of large structures that exceed the size of autoclaves, and in curing adhesive joints in cases where uniform radiation can be provided more easily than uniform heat. In industrial and consumer applications, multiple combinations of different reinforcing fibers can be co-cured in one cycle by EB with considerably lower residual stresses than those introduced by thermal cure.16... 

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. 

Yang I., Kuo M., Myers D., Pu A. Comparison of protein-based adhesive resins for wood composites. Journal of Wood Science 52 503-508 (2006). 

Wood Composites—these are resin-bonded composite boards where the particles are wood shavings, flakes, chips, or fibers bonded with thermosetting adhesives that can be urea formaldehyde, melamine formaldehyde, phenol formaldehyde, or diisocyanate. In recent years, the markets for OSB and MDF board have been rapidly increasing. Most particle board production uses urea-formaldehyde as a binder that is acid setting. Hence, sodium borates (alkaline) can interfere with the setting. As a result, boric acid has been the major boron compound used as the flame retardant in particle board.28 29 Typically, a loading of 12%-15% of boric acid in MDF is required to meet the ASTM E-84 Class A rating. If sodium borate is used as a flame retardant, phenol-formaldehyde binder, that is compatible with alkaline chemicals, is commonly used. 

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