[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.