Improving the Properties of Fast-Growing Chinese Fir by Vacuum Hot Pressing Treatment

Chinese fir was compressed by vacuum hot pressing and conventional hot pressing at different temperatures (180°C, 200°C and 220°C), respectively. The color parameters of the heat-compressed sample were measured, the relative mechanical properties of the material were tested and changes in the chemistry of fir were investigated using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results indicated that the color difference between compressed and untreated wood increased gradually with the increase of temperature. Compared with the conventional hot pressing treatment, the color difference (ΔE*) of the Chinese fir treated by vacuum hot pressing decreased by 43.73%, 69.91%, and 77.17%, respectively. The mechanical properties (bending elastic modulus and bending strength) of Chinese fir treated by vacuum hot pressing were signi ficantly improved. The 24-hour water absorption thickness expansion rate of fir treated by vacuum hot pressing is smaller than that of conventional hot pressing. It is implied that vacuum hot pressing treatment is an effective method to produce compressed wood, which can improve the mechanical properties and dimensional stability of wood, and reduce the in fluence of carbonization on wood color.