Dimensional stability acetylated wood

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,... 

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. 

Korai, H. (2001). Effects of low bondability of acetylated fibers on mechanical properties and dimensional stability of fiberboard. Journal of Wood Science, 47(6), 430-436. 

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. 

Ramsden, M.J., Blake, F.S.R. and Fey, N.J. (1997). The effect of acetylation on the mechanical properties, hydrophobicity and dimensional stability of Pinus sylvestris. Wood Science and Technology, 31(2), 97-104. 

Rowell, R.M., Simonson, R. and Tillman, A.-M. (1986b). Dimensional stability of particleboard made from vapor-phase acetylated pine wood chips. Nordic Pulp and Paper Research Journal, 1, 11-17. 

Rowell, R.M., Imamura, Y., Kawai, S. and Norimoto, M. (1989). Dimensional stability, decay resistance, and mechanical properties of veneer-faced low-density particleboards made from acetylated wood. Wood and Fiber Science, 21(1), 67-79. 

Rowell, R.M., Youngquist, J.A., Rowell, J.S. and Hyatt, J.A. (1991). Dimensional stability of aspen fiberboard made from acetylated fiber. Wood and Fiber Science, 23(4), 558-566. 

Figure 1 shows that the decay resistance of acetylated wood is directly proportional to the WPG (26). The degree of dimensional stability is also proportional to the WPG so the exclusion of cell wall or biological water may be a very important factor in the decay resistance mechanism. 

Acetylation of cellulose to the triacetate has been carried out without breaking down of the structure with acetic anhydride containing pyridine to help open up the cell wall structure and to act as a catalyst (71). This led Stamm and Tarkow (72) to test the liquid phase reaction on wood. High dimensional stabilization without break down of the structure was obtained, but excessive amounts of chemical were used. They hence devised a vapor phase method at atmospheric pressure that proved suitable for treating veneer up to thicknesses of 1/8 inch. Acetic anhydride pyridine vapors generated by heating an 80-20% mixture of the liquids were circulated around sheets of veneer suspended in a box lined with sheet stainless steel. Hardwood veneer,... 

USDA, Forest Service, Forest Products Laboratory, FPL GTR-55 Rowell RM, Imamura Y, Kowai S and Norimoto M (1989) Dimensional stability, decay resistance and mechanical properties of veneer faced low-density particlehoards made from acetylated wood. Wood and Fiber Science, 27(1)67-79 Rowell RM, Kawai S and Inone M (1995) Dimensionally stabilized, very low density fibreboard. Wood and Fiber Science, 27(4) 428-36 Rozsa AN (1994) Dielectric vacuum drying of hardwood. Proceedings 4th lUFRO International Drying Conference, Rotorua, New Zealand, 271-8 Ruddick JNR (1987) Proceeding of the incising workshop, Richmond, British Colombia, 1986. Special Publication 28. Forinteck Canada Corp., Vancouver, BC... 

A commercial plant (Titan Wood) has started to produce acetylated wood and has given the acetylated wood the name of a new wood species Accoya . Improved properties are high durability, high dimensional stability and high UV-resistance. ... 

Acetylation methods have been used for many years to improve some properties of wood cellulose such as moisture repellency, dimensional stability and resistance to environmental degradation. Their use for improving the properties of natural fibers has increased significantly in the last decade or so. The methods are based on the reaction of lignocellulosic material with acetic anhydride at elevated temperature, with or without a catalyst. The acetic anhydride reacts with the more reactive hydroxyl groups according to the equation [36],... 

The effect of acetic, maleic or snccinic anhydride modifications of wood fibre on the mechanical properties and dimensional stability of differently bonded fibre boards was studied [33]. The binders for the fibreboards used in that work were powdered PF resin of the novolak type, PP and a combination of the two. Significant improvement in the mechanical properties was obtained as a result of the anhydride modifications. Thus, modification of wood fibres with maleic anhydride (MA) resulted in a reduction in the modulus of rupture of the PF and PF/PP-bonded boards, whereas acetylation and modification with succinic anhydride did not cause any significant changes in the modulus of rupture of the boards. The anhydride modifications improved the internal bond strength of the binder type used. Dimensional stability of the fibreboards was observed to increase significantly as result of the modifications [33]. 

Acetylation treatment of natural fibers is originally applied to wood cellulose to stabilize cell walls against moisture, improving dimensional stability and envirormiental degradation [73]. Therefore, acetylation may contribute toward decreasing the moisture absorption of natural fibers [37]. Plasticization of cellulose-based natural fiber can be introduced by this treatment, which is related to an esterification method. During the treatment of natural fibers with acetic anhydride, the hydroxyl groups... 

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