Effects of fumigation treatment on wood color and mechanical strength of Larix gmelinii

In order to study the influence of fumigation processing on wood color and mechanical properties of wood, three kinds of fumigants (carbonyl sulfide, COS; methyl bromide, MB; sulfuryl fluoride, SF) were used to process larch (Larix gmelinii) in three different mass concentrations, and the color difference detection, scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and Fourier transform infrared (FTIR) spectroscopy were used to analyze the fumigation treatment influence on physical and chemical properties of larch samples. The results showed that: 1) larch wood color was altered obviously after fumigation treatment, and COS fumigation treatment had minimal impact on brightness (L^*), red and green chromaticity index (a^*). 2) After COS fumigation treatment, the compression strength parallel to the grain, the bending strength and the elastic modulus of samples decreased significantly, and compressive strength had the greatest reduction at condition of mass concentration at 124.2 g/m³, decreased by 13.09%, and the bending strength and the elastic modulus of samples fell by 9.38% and 8.66%, respectively. After MB fumigation and SF fumigation treatment, the compression strength parallel to the grain, the bending strength and the elastic modulus of samples hardly changed. 3) After fumigation processing, the surface microstructure of samples was maintained, but the surface S and F element distribution slightly increased after COS and SF fumigation treatment. 4) In the infrared spectroscopy of larch wood, the C O and C—H bonds increased after MB and SF fumigation processing. After COS fumigation processing, the C O stretching vibration of hemicellulose became weakened, but the C O stretching vibration of aromatic ring skeleton became stronger, and the content of lignin increased.