Preparation And Properties Of Compressed Preservative-treated Wood (CPW)

In this study, the sapwood, heartwood and the mixed of sapwood and heartwood of Chinese fir(Cunninghamia lanceolata Hook.) pretreated with different hydrothermal treatment were immersed in the ammine copper quat-type D (ACQ-D) preservative solution to get compressed preservative-treated wood (CPW). Both the physical mechanical properties as well as the penetration especially that of heartwood have improved. The results showed that:1) Three different pretreatments of water bathing, spraying and steaming have been chosen. The liquid absorption and the recovery rate of compression deformation as well as the surface hardness, the distribution of density and CuO retention in the thickness direction of CPW were determined. It can be seen that the pretreatments would soften cell wall avoid damaging during compression. The optimum pretreatment has been obtained by orthogonal analysis of temperature and time when steaming on the samples, which is steaming 60min at 120℃, and soaking in water at 80℃.2) The recovery rate and liquid absorption were closely related with each other. Generally a higher recovery rate of compressed deformation corresponded to a higher liquid absorption, as well as a lower surface hardness, however, when the compression time increased in a certain range, there would be little effect on the surface hardness. The density distribution of the CWP and the retention of CuO appeared to be much higher and had a clear trend of higher retention on surfaces and lower inside. The higher the density, the more the absorption site existed in the cell wall.3) Compression speed had a great effect on the performance of CPW. Higher compression speed of 3 mm·min-1 was preferable since the samples compressed under that speed could reach the highest Al and Ac; in addition, less deformation fixation has been produced possibly because there would be more fixed matrix that was quite easily effected and hydrophobic bonds when compressed at lower speed, leading to a lower recovery.4) ACQ-D penetration of sapwood and heartwood can be improved by compression. The liquid absorption of compressed wood was about 1.5 times of the untreated control samples; the copper retention within 2 mm in the heartwood was almost the same as that in the sapwood, showing a much deeper penetration in the heartwood than that of UC.5) The decay resistance of heartwood, untreated and treated sapwood with preservative ACQ-D at different concentration were tested and analyzed by weight loss, in order to determine the matchable retention of ACQ-D in the sapwood comparing with the heartwood's durability.