Particleboard water

El-particleboard- and El-MDF-resin for water-resistant boards (EN 312-5 and 312-7 [2]). For boards according to option 1 (V313-cycle test) MUF-resins can be used for boards according to option 2 (VI00-boiling test) MUPF with approval are necessary. In case, espeeially for the MDF-production, formaldehyde catchers are added. 

European Norm EN 1087-1, Wood particleboard. Determination of resistance to humidity. Boiling water test, 1997. 

Articles made from amino resins are water clear, hard, and strong, but they can crack. They have good electrical properties, and they have better colorability than phenolic resins. Amino resins are used as adhesives for plywood and particleboard but only in interior grades. They have low weather resistance and deteriorate when exposed to sun, heat, cold, and moisture. 

In a similar five-cycle water-soaking/ovendrying test on bamboo particleboards, control boards swelled more than 30 percent, while boards made from acetylated particles swelled about 10 percent. 

Adhesive. Urea-formaldehyde water-based dispersions are the most widely used particleboard binders. The low-cost, rapid curing, and colorless properties of urea-formaldehyde adhesives make them the adhesive of choice for most interior particleboard. These adhesives have been continuously improved by the resin manufacturers, resulting in reduced press times without detrimental effects on their storage life or handling characteristics. 

Wax Emulsions. The final component in most particleboard is a sizing agent to reduce the absorption of liquid water. This is normally a paraffin wax emulsion which is supplied to the particleboard manufacturers at approximately a 50 percent wax solids in water. Less than 1 percent wax solids based on the ovendry wood weight is used in most particleboard levels above 1 percent tend to interfere with interparticle bonding while levels below 0.75 percent do not offer maximum water resistance. 

Dost in 1971 reported on a study where redwood bark fiber was used in three-layer particleboard (44). Amount of bark in the furnish, by weight, was 0, 10, 20, and 30% hammemilled disk flakes or Pallmann flakes of redwood wood made up the remainder of the furnish. Urea formaldehyde resin was applied at three percentages. Test results showed surface smoothness and strength properties (MOR, MOE, and IB) decreased with increasing bark content in the boards. Water absorption decreased, but thickness swelling and linear expansion increased as the amount of bark increased. 

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... 

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]. 

It is of interest that veneer-faced low-density particleboards made from acetylated veneers and acetylated core particles showed excellent dimensional stability in both liquid water and humidity tests and were resistant to attack by fungi in an 8-week soil block test [57]. Furthermore, during the 150-day bending-creep test, the totally acetylated boards showed no strength or weight loss during exposure to T. palustris. 

Figure 26 Water resistance of particleboards containing combination of chemically modified particles. Abbreviations are the same as in Fig. 25. Note samples were immersed in water for 24 h at 25°C.

Great]y improved resistance to biological attack has been achieved aLso in particleboards made from PF resin-impregnated particles of Japanese cedar [65,66]. Particles had average dimensions of 0.43 mm in thickness, 2.83 mm in width, and 29.6 mm in length. They were oven-dried until moisture content reached about 3%. A water-soluble PF resin of Mn 389 was used for the treatment of particles. Two methods were employed for incorporating the resin into the particleboards method I—pretreatment by dipping of particles... 

Hygroscopic thickness swelling Water absorption JIS A 5908 Particleboards 5.8 Hygroscopic thickness swelling test... 

The response to water is critical in applications where water exposure occurs. Both particleboard and MDF ultimately fail unless moisture is excluded, limiting applications to those areas where the chance of this occurring is small. Most applications in furniture, fittings and cabinetry meet this requirement. There are also applications where structural performance is not usually critical, that is where a failure of the item does not endanger the structure as a whole. 

Maxwell JW Gran G and Waters GD (1984) Experiments with blowline blending for MDF. In Maloney T (ed). Proceedings of the 18th Washington State University Particleboard S)nnposium, Pullman, Washington, 117-43... 

Roffael (15) measured formaldehyde emissions from a phenolic particleboard using the WKI-Method which involves suspending small samples over 50 cm of distilled water in tightly closed polyethylene bottles and measuring formaldehyde levels in the water after varying times. Temperatures were maintained at 42 C. This work indicated that formaldehyde release from the phenolic particleboards ceased after a relatively short reaction period (approximately 96 hours). This finding is consistent with the resin stability considerations discussed previously under theoretical considerations. 

Figure 9. Formaldehyde liberation in water at 25 C and pH 3 from particleboard and CH20-sorbed wood all materials -80 mesh. (Sodium azide in water at 100 mg/L as preservative symbols and abbreviations as in Figure 7.) (ML85 5436)...

Figure 11. Formaldehyde loss ratios at 80 percent relative humidity (RH) and in water. (Loss ratio = CH2O liberated relative to that from urea-formaldehyde particleboard in same test.

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