Prediction of Oriented Strand Board Wood Strand Density by near Infrared and Fourier Transform Infrared Reflectance Spectroscopy

Abstract

The objective of this research was to calibrate and compare the ability of near infrared (NIR) and Fourier transform infrared reflectance (FT-IR) to predict strand density. Four hundred and fifty flakes were randomly selected, measured for density, and then 99 flakes (33 = low, 33 = medium and 32 = high density) were selected for calibration and cross-validation through the predicted sum of squares ( PRESS) method. This research found that calibration equations from NIR spectra ( R2= 0.82; RMSEP=0.059 g cm−3) was superior to equations developed from FT-IR ( R2= 0.68; RMSEP=0.076 g cm−3) when the same number of factors were used. Using a first-derivative pre-treatment, five factors were necessary to predict strand density from NIR spectra despite a random tracheid (wood cell) orientation. Lignin-associated wavelengths (range, 1660–1670 nm) provided the most leverage in predicting strand density although crystalline and amorphous components of cellulose also played a role. The prediction of density above 0.65 g cm−3was inaccurate for both NIR- and FT-IR-based models. The bias was attributable to the additional absorbance that occurred at higher densities.