368
T. Ma et al.
16.2.7 Wood Modification and Degradation
Wood modification and degradation are other great topics. Wood is a hygroscopic
natural material, and cell wall moisture adsorption or desorption occurs until an equilibrium moisture content (EMC) is reached in response to variation in surrounding
relative humidity and temperature. Such sorption behaviors influence the stability of
the wood dimension and mechanical properties. Hence, wood modification typically
required before using. For example, when wood is treated with acetic anhydride,
the hydroxyl groups of lignin, hemicelluloses, and cellulose are replaced with acetyl
groups, and it has the advantages of dimensional stability, decay resistance to fungi.
Schwanninger et al. reported that the chemical changes in wood due to acetylation
could be monitored by NIRS [33]. Green et al. utilized NIRS for accessing wood
decay in pine sapwood wafers [34]. Experimental results showed a strong correlation
between NIR spectral data and sample mass loss, compression strength, and early
stages of wood decay. Sandak et al. developed an FT-NIR-based methodology for
estimating the biodegradation rate of recycled paper [35]. There were significant light
absorption differences that correspond to C–H and O–H functional groups of cellulose. They found a good agreement between spectroscopic and reference methods
(microscopy, mechanical testing, mycological tests). Inagaki et al. measured NIR
reflectance spectra from the wood samples heated at 90, 120, 150, and 180 °C from
5 min to approximately 1.4 years. Kinetic analysis of principal component scores
was useful to understand the chemical change in the thermally treated wood samples
[36].
16.2.8 Wood Pulp and Paper
NIRS has been traditionally used in the quality analysis of pulp and paper. Downes
et al. reported to predict Kraft pulp yield and cellulose content in Eucalyptus wood
using NIRS [37]. Gigac and Fiserova indicated that NIR spectra could be used to
predict the filler content, Kappa number, and strength properties of raw materials
and paper [38]. Meder et al. compared the performance of laboratory and handheld
NIR instruments in predicting Kraft pulp yield in standing trees (5 mm or 12 mm
increment cores). The results showed the handheld NIR devices were also capable of
predicting cellulose content and Kraft pulp yield [39]. Tyson et al. indicated that the
tightly regulated pulping processes reduce the variability of the pulps, which affect
on constructing physical and mechanical prediction models based on NIR spectra
[40]. Yonenobu et al. [53] pointed out that NIRS was powerful in investigating the
chemical condition of washi (literally “Japanese paper,” which has played a vital
role in Japanese culture since the early eighth century). This approach had obtained
satisfactory results with conventional sugar analysis.
T. Ma et al.
16.2.7 Wood Modification and Degradation
Wood modification and degradation are other great topics. Wood is a hygroscopic
natural material, and cell wall moisture adsorption or desorption occurs until an equilibrium moisture content (EMC) is reached in response to variation in surrounding
relative humidity and temperature. Such sorption behaviors influence the stability of
the wood dimension and mechanical properties. Hence, wood modification typically
required before using. For example, when wood is treated with acetic anhydride,
the hydroxyl groups of lignin, hemicelluloses, and cellulose are replaced with acetyl
groups, and it has the advantages of dimensional stability, decay resistance to fungi.
Schwanninger et al. reported that the chemical changes in wood due to acetylation
could be monitored by NIRS [33]. Green et al. utilized NIRS for accessing wood
decay in pine sapwood wafers [34]. Experimental results showed a strong correlation
between NIR spectral data and sample mass loss, compression strength, and early
stages of wood decay. Sandak et al. developed an FT-NIR-based methodology for
estimating the biodegradation rate of recycled paper [35]. There were significant light
absorption differences that correspond to C–H and O–H functional groups of cellulose. They found a good agreement between spectroscopic and reference methods
(microscopy, mechanical testing, mycological tests). Inagaki et al. measured NIR
reflectance spectra from the wood samples heated at 90, 120, 150, and 180 °C from
5 min to approximately 1.4 years. Kinetic analysis of principal component scores
was useful to understand the chemical change in the thermally treated wood samples
[36].
16.2.8 Wood Pulp and Paper
NIRS has been traditionally used in the quality analysis of pulp and paper. Downes
et al. reported to predict Kraft pulp yield and cellulose content in Eucalyptus wood
using NIRS [37]. Gigac and Fiserova indicated that NIR spectra could be used to
predict the filler content, Kappa number, and strength properties of raw materials
and paper [38]. Meder et al. compared the performance of laboratory and handheld
NIR instruments in predicting Kraft pulp yield in standing trees (5 mm or 12 mm
increment cores). The results showed the handheld NIR devices were also capable of
predicting cellulose content and Kraft pulp yield [39]. Tyson et al. indicated that the
tightly regulated pulping processes reduce the variability of the pulps, which affect
on constructing physical and mechanical prediction models based on NIR spectra
[40]. Yonenobu et al. [53] pointed out that NIRS was powerful in investigating the
chemical condition of washi (literally “Japanese paper,” which has played a vital
role in Japanese culture since the early eighth century). This approach had obtained
satisfactory results with conventional sugar analysis.