Studies on pre-treatment by compression for wood impregnation II: the impregnation of wood compressed at different moisture content conditions

Abstract

As a follow-up report, the impregnation of wood pre-treated by compression at different moisture content (MC) conditions was systematically studied in terms of impregnation during the release of compression and impregnation after release of compression. The results showed that for poplar with MC from 210 to 38.9% and Chinese fir from 175 to 43%, the impregnation during and short time after the compression release increased rapidly and increased slowly afterward. The impregnation during the compression release accounted for a rather large portion of the total impregnation, while took a short time, suggesting that the pre-treatment by compression was very significant in terms of impregnation time and amount for wood above fiber saturation point. The specimens with higher MC before compression tended to reach the maximum impregnation in shorter time than those with lower MC. The impregnation during the release of compression decreased with the decrease in MC before compression. The impregnation after the release of compression increased with the decrease in MC for poplar, while decreased first and then increased for Chinese fir. As a result, when the MC was higher than maximum moisture content allowed (MMCA), with the decrease in MC, the total impregnation decreased from 0.45 to 0.30 g/cm3 for poplar and from 0.30 to 0.07 g/cm3 for Chinese fir; when the MC was lower than MMCA, with the decrease in MC, the total impregnation increased from 0.30 to 0.38 g/cm3 for poplar while from 0.07 to 0.16 g/cm3 for Chinese fir. After all, by means of pre-treatment of compression, wood with a MC around MMCA tended to have the lowest impregnation.