Study On The Color Change And Mechanical Properties Of Heat-treated Southern Pine Wood By Fourier Transform Near-Infrared Spectroscopy

In order to develop a simple,rapid and efficient method to accurately predict the wood properties,A near infrared spectroscopy technology coupled with chemometrics methods was used to build prediction models which were exploited to predict color changes and mechanical properties of heat-treated southern pine wood.The benzene-alcohol extractives,cellulose,a-cellulose,lignin of the southern pine wood samples heated with 120?,180?,220? and untreated were analyzed quantitatively according to traditional chemical analysis method.Color changes of the untreated and heat-treated wood were measured by CIE1976 L^*a^*b^*colorimetric parameters.Color prediction model coupled with chemometrics method was built through collecting near infrared spectroscopic information on tangential section of wood samples.The modulus of rupture?MOR?and the modulus of elasticity?MOE?of wood samples were measured by three-point bending test for heat treated and untreated southern pine wood.The MOR and MOE prediction models were established by using the partial least squares method and the cross test method.The results obtained are showed as follows:The color prediction models established by measuring the brightness?L^*?,the red-green axis parameter?a^*?,the yellow-blue axis parameter?b^*?showed that the determined coefficient?R²?and the root mean square error of prediction?RMSEP?were 0.947 and 3.08,0.924 and 0.46,0.961 and 0.985 for L^*,a^*and b^*,respectively.The MOR prediction models established showed that the R² and the RMSEP were 0.910 and 6.53,0.834 and 8.83,0.799 and 9.75 on transverse,radial and tangential section,respectively.Also,The MOE prediction models established showed that the R² and the RMSEP were 0.899 and 527,0.772 and 884,0.781 and 871 on transverse,radial and tangential section,respectively.Of all the mechanical prediction models,the models established on transverse section which was containing more abundant spectral information than other two sections showed better prediction effort for heat-treated southern pine wood,showing it was feasible by NIRs to predict mechanical properties of wood.By analysis of NIR spectrum,changes of wood color and mechanical properties resulted from degradation and subsequent chemical reaction of degradation products,including such as stretching vibration of C=O at 5245cm^-1 assigned to hemicellulose,stretching vibration of C-O at 4404cm^-1 assigned to hemicellulose and cellulose,and vibration of aromatic ring carbon skeleton at 5663 cm^-1 and 5890cm^-1 assigned to lignin.The results of the color-strength equivalence analysis of the heat-treated wood showed that it was feasible to predict the mechanical strength of the heat treatment by the wood color change.