Effect of temperature on color and chemical composition of poplar powder compacts during warm-press forming

The color parameters of untreated wood powder and wood powder after warm-press forming were measured according to standard colorimetric systems. The composition of the sample was tested by wet chemistry technique. The chemical compositions of the sample after warm-press forming were analyzed by using X-ray photoelectron spectroscopy (XPS) and UV–Vis. The results showed that as the forming temperature increased, the lignin, the extracts and the absorption in the visible range increased, while the cellulose and the O/C values decreased. Besides, the color of the sample became darker. The changes in the chemical composition on the surface of the wood powder compact induced the color change.