Resumo:
This study addresses the bleaching process of Pinus wood with the purpose of evaluating its application in the manufacture of transparent wood (MT), a composite made up of bleached wood and polymer resin. The removal of wood color was achieved by modifying the chromophore groups present in lignin, using hydrogen peroxide in conjunction with ultraviolet radiation. In this context, the parameters of the bleaching process were investigated, including the concentration of hydrogen peroxide, the immersion time of the wood samples in the solution and the period of exposure to ultraviolet radiation. A two-level experimental design (23) was used to evaluate the effect of these variables on the whiteness index (WI) of the samples. The chemical treatment applied to Pinus wood resulted in a significant increase in WI, from 13.30 to 60.55, as well as in porosity, which increased from 49.44% to 69.88%, consistent with the reduction in wood density, from 0.38 to 0.17 g/cm³. As predicted, the fundamental components of the wood were preserved after the bleaching process, which was evidenced by the characteristic absorption bands of the chemical structures of cellulose, lignin, and hemicellulose in the FTIR spectrum of the sample. This analysis corroborates the color changes resulting from the removal of chromophore groups from lignin and the chosen bleaching method. Bleached Pine wood was impregnated with epoxy resin under vacuum, resulting in a material with transmittance of 77.66%. The results obtained indicate the viability of this process to produce MT from Pine.
