[Modified Mechanism of Cell Walls from Chinese Fir Treated with Low-Molecular-Weight Phenol Formaldehyde Resin].

Study on the modified mechanism of wood cell walls, it is very important for improving treatment reagents, optimizing treatment technology, and enhancing wood density, mechanical properties, dimensional stability, and so on. Samples of plantation Chinese fir were treated gradually with synthesized water-soluble low-molecular-weight phenol formaldehyde (PF) resins under vacuum and pressure. The correlated physical and chemical properties of the treated and untreated reference samples were determined by X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FTIR), and nuclear magnetic resonance spectrometer(NMR) (Using method of Cross Polarization/Magic Angle Spinning for continuous testing) with high precision and resolution. The results showed that, after treated with water-soluble low-molecular-weight PF resin, the average values of crystallinity from the treated samples were decreased obviously, and the average reduction rate was 12.67%, 11.91% and 6.26%, respectively. Comparing water-soluble, low-molecular-weight PF resin modified Chinese fir with untreated reference samples, no new chemical shifts and characteristic peaks of functional groups from esters, ethers, etc. were present by using FTIR and ¹³C NMR spectrum. It was considered that there was no distinct chemical reaction between the water-soluble low-molecular-weight PF resin and Chinese Fir cell walls. But water-soluble low-molecular-weight PF resin could enter into the structure relatively loose, large size spaces, relatively area large amorphous regions in cell walls of Chinese fir tracheids, and form physical filling, which resulting in the decreasing of relative crystallinity. This study has important reference value for the development of new wood modification reagents and the optimization of wood modification process. The findings also provide important theoretical foundation for further proving the modification mechanisms of wood cell walls and enriching the modified theories of wood cell walls.

[Influence factor for prediction of air-dry density of Eucalyptus pellita by near infrared spectroscopy].

Near infrared spectroscopy(NIR)technique was applied to compare the influence factors of Eucalyptus pellita's air-dry density. Air-dry density of eucalypt wood was tested by direct measurement After collecting the near infrared reflectance spectra of samples in different section and with different thickness, moisture content and roughness, the NIR spectra were preprocessed with the second-derivative and the regression models were built in certain spectra. The calibration models were established using 50-140 samples with the partial least squares method and validated with external validation method. The results showed that the predicted results were influenced by sample's section, thickness, roughness and moisture content. The best near infrared spectroscopy prediction model was built under the condition of transverse section, 2-5 mm thickness, 12% moisture content and meticulous roughness of wood.

[Prediction of the lengths of fibers and vessels of rattans using near infrared spectroscopy].

The morphological characteristics of fibers and vessels of six rattan species in Southern China were investigated to study the feasibility of predicting the lengths of fibers and vessels of rattan species with application of analytical technologies of near infrared spectroscopy (NIR). The results showed that the average lengths of fibers and vessels of six rattan species were from 1 229 to 1 917 mm and from 1 035 to 2 129 mm, respectively. The models of length of fiber and vessel were constructed by combining partial least square (PLS) and full cross-validation, and a good correlation between the length of fibers and the spectrum transformed by the first derivative was found within the spectral range of 350 - 2 454 nm, and the correlation coefficient (r(c) and r(p)) and standard error (SEC and SEP ) of calibration model and prediction model are 0.98, 0.85 and 70, 178 respectively, while a good correlation between the length of vessels and the spectrum transformed by the first derivative was found within the spectral range of 350-2 500 nm, the correlation coefficient (r(c) and r(p)) and standard error (SEC and SEP) of calibration and prediction model is 0.97, 0.80 and 101, 261 respectively. Their model parameters showed that NIR spectroscopic technique can rapidly and accurately predict the lengths of fibers and vessels of the six rattan species.

[Microfibril angle prediction of Eucalyptus pellita wood samples based on radial and tangential section by near infrared spectroscopy].

Near infrared spectroscopy (NIR) technique was applied to predict wood microfibril angle (MFA) of eucalyptus pellita in radial/tangential section. The MFA of small clear increment core samples were measured by X-ray diffractometry. After collecting the near infrared reflectance spectra of each sample, the NIR spectra were preprocessed with the second-derivative and the regression models were built for certain spectra. The calibration models were established using at least 159 samples with the partial least squares method and validated with full cross validation method. The results showed that high correlation coefficients were obtained between the laboratory-determined data and NIR fitted data. The finding suggests that an NIR instrument could be calibrated to estimate the limited MFA range of the increment core samples of eucalyptus pellita in radial/tangential section rapidly. Further work is required using different species wood sample sets that display a wide range of MFA variation.

[Estimation of modulus of elasticity of Eucalyptus pellita wood by near infrared spectroscopy].

In the present study, the rapid prediction of wood modulus of elasticity (MOE) of Eucalyptus pellita by near infrared (NIR) spectroscopy is described. Fast Fourier transform (FFT) and conventional mechanical testing methods were used to measure modulus of elasticity of small clear wood samples of Eucalyptus pellita. After collecting the near-infrared reflectance spectra of each sample from radial and tangential faces, the NIR spectra were preprocessed with the second-derivative methods, and regression models were built between 410 to 2 480 nm. The calibration models were established using two thirds of whole samples with the partial least squares method, and validation models were developed on an independent set (one third of whole samples). The analysis results showed that high correlation coefficients were obtained between the laboratory-determined MOE values and NIR prediction values of Eucalyptus pellita. The correlation coefficients of prediction model for MOE were 0.93 and 0.81, and RPD were 2.70 and 1.71. NIR analysis technique can realize the rapid prediction of the MOE of small clear wood samples of Eucalyptus pellita.

[Comparison of four kinds of measurement techniques for wood microfibril angle].

X-ray diffraction technique, pit aperture observing technique, polarized light microscope technique and near infrared spectrum technique were used separately to test the wood microfibril angle of Chinese fir, and the results were as follows: For the identical tree of Chinese fir, the average microfibril angle obtained by the polarized light microscope technique was the biggest, followed by those obtained by X-ray diffraction technique, and then by polarized light microscope technique, but the difference in the average microfibril angle was not significant. For the different annual rings, the microfibril angle obtained by X-ray diffraction technique became the biggest after the 20th annual ring, the fluctuation of the microfibril angle got by the pit aperture observing technique were big, but the fluctuation got by the polarized light microscope technique was just the reverse. The measurement value curves got by the three techniques were fitted well, and the difference in the average microfibril angle was not significant between different annual rings. For the microfibril angle of the same annual ring, the difference between the maximum and the minimum value tested by the polarized light microscope technique was less than 4 degrees, but the difference tested by the pit aperture observing technique achieved 21.53 degrees, and the standard deviation achieved 4.75. The near infrared spectrum and the Xray diffraction techniques were all called nondestructive testing techniques. The model set up by the two techniques was very good because of its high prediction and repeatability, and the model was also good for online analysis. The R2 of calibration model and tested model achieved 0.81 and 0.75 respectively,and the standard error of calibration and prediction were 1.79 and 2.02 respectively. In addition, the near infrared spectrum technique could be also used with the other three techniques to predict the wood microfibril angle, showing the superiority of the near infrared spectrum technique. Meanwhile, the advantages and shortcomings were analyzed for the four kinds of measurement techniques.

[FTIR and XPS spectroscopic studies of photodegradation of Moso Bamboo (Phyllostachys pubescens Mazel)].

The photodegradation process of bamboo involves very complex chemical reactions. In the present study, surface deterioration of Moso bamboo (Phyllostachys pubescens Mazel) was carried out by a xenon fade meter which can simulate sunlight irradiation, and Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopic (XPS) techniques were used to characterize the resulting changes in the chemical structure and composition of bamboo surface. XPS results showed that light irradiation resulted in significant increases in oxygen (O) content and O/C ratio. Besides, changes were also identified from the detailed C(ls) spectra, with a remarkable decrease in C1 component (C-C) and simultaneous increases in the components of C2 (C-O), C3 (C = O) and C4 (O-C = O), suggesting that the carbon atoms at bamboo surface were highly oxidized. FTIR results showed that lignin was susceptible to light irradiation and was significant degraded after treatment, as indicated by remarkable decreases in the intensity of lignin associated bands (e. g. 1 604, 1 512 and 1 462 cm(-1)). This was accompanied by the formation of new carbonyl compounds as shown by an obvious increase in the intensity of non-conjugated carbonyl group at 1 735 cm(-1), which further indicated the photo-oxidation of bamboo surface. The polysaccharides (cellulose and hemicellulose) components, however, were less influenced by light irradiation, and their relative content at bamboo surface increased significantly due to lignin degradation.