Particle board dimensional stability

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,... 

Fuwape, J.A. and Oyagade, A.O. (1999). Strength and dimensional stability of acetylated Gmelina and Sitka spruce particle board. Journal of the Timber Development Association of India, 45(1/2), 5-10. 

Common grades of laminates tend to be thin materials ranging from 0.5—1.5 mm in thickness, therefore for most applications they must be supported. In the manufacture of furniture, cabinetry, and countertops the laminates are bonded to particle board or plywood. Since the laminates consist largely of cellulosic paper, their dimensional stability is similar to wood, particularly to particle board. 

Boards exhibiting excellent dimensional stability and internal bonds vie re produced using 3 and % NO, Once again it appears that splinter-type particles rather than flakes give highest internal bonds. Densities of all boards reported ranged from 0 73 to 0.78, Molar ratios of furfuryl alcohol to formaldehyde used vieve approximately 3 2. 

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. 

In the manufacture of cement-bonded particle board, wood chips are mixed with Portland cement in the ratio 60% cement, 20% wood and 20% water. Curing times are very long - about 7 h at 70-80 °C, followed by a further 2-3 weeks conditioning at ambient temperature. The boards produced have high density (1300 kg m , double normal particle board), but have exceptional dimensional stability, moisture and fire resistance compared to other wood-based boards. 

Some of the composites have also been in the consumer market for some time. In addition to plywood, homebuilders and furniture makers are making extensive use of particle board (woodchips in a polymer matrix) because of its superior dimensional stability. Often it is laminated to a wood veneer for use as furniture. Decorative vinyl-clad steel or aluminum panels are used in office buildings. Generally, the more advanced composites such fiber-reinforced metals and ceramics have been too expensive for... 

---