Volume 67, Issue 3

No abstract available.

Japanese beech ( Fagus crenata ) has been liquefied by water-added subcritical phenol without a catalyst in a batch-type reaction vessel. The effect of water/phenol ratio was studied under conditions of various treatment times. The fractions soluble in phenol/water as well as the insoluble residues were characterized. Liquefaction kinetics was investigated assuming the validity of the first-order reaction rate law. The degree of phenolation was increased with increasing treatment times and water content in phenol/water solvent. Treatment at 270°C under 3.1 MPa pressure for 10 min with a water/phenol ratio of 25:75 gave the best liquefaction result. Various oligosaccharides derived from cellulose and hemicelluloses were found to be hydrolyzed and solubilized in the water-soluble portion.

A selective cleavage method for β-O-4 linkages (the γ-TTSA method) was introduced in previous works, which consists of four reaction steps: (1) γ-tosylation, (2) thioetherification, (3) sulfonylation, and (4) mild alkali degradation. This method was applied to the degradation of a lignin polymer model (dehydrogenation polymer, DHP) consisting of guaiacyl units. Each reaction step was followed by Fourier transform infrared (FT-IR) spectroscopy and heteronuclear single quantum coherence nuclear magnetic resonance (HSQC-NMR) spectroscopy. It was demonstrated that only the β-O-4 linkage was selectively cleaved by the γ-TTSA method, although other linkages, such as β-5 and β-β linkages, were also present in the DHP. Consequently, the γ-TTSA method is expected to be also useful for the degradation of native lignins.

Totally chlorine free (TCF) pulp with a high content of hexenuronic acids (HexAs) was found to possess a high antioxidant power. The contribution of HexA to kappa number in unbleached Eucalyptus globulus kraft pulp was estimated to be 1.05 units per 10 μmol of HexA. The variation of HexA and lignin contents in enzymatic elemental chlorine free (ECF) and TCF sequences was monitored, and interesting effects were observed during the TCF XLE sequence, where X denotes an enzyme pretreatment with xylanase, L a laccase-mediator stage, and E an alkaline extraction stage. Thus, HexA removal during L stage was strongly enhanced after the X stage; also, the HexA content was decreased by the alkaline stage. None of these effects was observed in the ECF sequence with chlorine dioxide. The antioxidant power detected in HexA makes TCF pulp an excellent raw material for manufacturing packaging for easily oxidized products.

The problems related to the determination of the absolute molecular weight ( M w ) of sodium lignosulfonate (NaLS) are the focus of the present work. Four narrow-dispersed NaLS fractions were collected by filtration, ultrafiltration, and gel permeation chromatography (GPC), and their M w measured by laser light scattering (LLS M w ) was compared with that obtained by GPC (GPC M w ). The LLS M w values were much larger than GPC M w , and this M w difference increased with increasing M w of NaLS. This finding confirms the known polyelectrolyte and aggregation effects of NaLS. The deviation is also partly due to the conformation differences between the GPC standard (sodium polystyrene sulfonate) and the NaLS molecules. The effects of polyelectrolytes and NaLS aggregates could be inhibited by adding enough NaCl salt in the NaLS solution and filtering the NaLS/NaCl solution through a syringe filter. As a result, the slow mode in dynamic LLS measurement disappeared. By this approach, the absolute LLS M w values were only slightly larger than that determined by GPC due to the conformation differences between the GPC standard and the NaLS molecules.

Norway spruce ( Picea abies ) has been submitted to oscillatory ball milling at room temperature and at -196°C. The effects of moisture content (MC) and cryogenic milling on the morphology and crystallinity of cellulose were investigated. At room temperature, MC had a significant effect on particle morphology and it was possible to produce powders of smaller particle size and rounder shape when the wood feed had a lower MC. Under cryogenic conditions, MC had less influence on the morphology, and the particle size was even smaller than that produced under ambient conditions. The degree of cellulose crystallinity in the milled wood was influenced by the MC of the feed, milling time, and milling temperature.

Recovery of metals from chromated copper arsenate (CCA)-treated southern pine wood particles was investigated by extraction in a microwave reactor with binary combinations of acetic acid (AA), oxalic acid (OxA), and phosphoric acid (PhA). Use of OxA was not successful, as insoluble copper oxalate complexes impeded copper removal. The combination of OxA and AA also had adverse effects on copper extraction. In contrast, the combination of AA and PhA enhanced the chromium recovery rate. The highest recovery rate of metals could be achieved with a mixture of 2.75% PhA and 0.5% AA at 130°C for 10 min in the microwave oven. The total recovery rate approached 100% for arsenic, 96.7% for chromium, and 98.6% for copper in a one-step process.

Distributions of nuclear magnetic resonance (NMR) relaxation times provide detailed information about the moisture absorbed in wood. In this work, T 2 *, T 2 , and T 1 distributions were recorded from fresh sapwood and heartwood samples of pine ( Pinus sylvestris ) and spruce ( Picea abies ) at various temperatures. Below the melting point of bulk water, free water is frozen and its signal disappears from the distributions. Then, the low-temperature distributions of the unfrozen bound water contain more information about its components, because the large free water peaks hiding some smaller bound water peaks are absent and the exchange between free and bound water is prevented. Comparison of the total moisture signal integrals above and below the bulk melting point enables the determination of fiber saturation point (FSP), which, in this context, denotes the total water capacity of cell wall. T 2 *, T 2 , and T 1 distributions offer different kinds of information about moisture components. All the peaks in the distributions were assigned, and it was demonstrated that the accessible hydroxyl site content and the amount of micropores can be estimated based on the peak integrals.

The sound transmission loss (STL) of precipitated calcium carbonate (PCC)-filled wood plastic composite (WPC) was studied using a numerical analysis method based on the mass law and sound scattering theory. Several physical models for explaining sound wave transmission in WPC were established, and relevant STL equations were derived. The STL of WPC filled with different PCC weight ratios was analyzed using these models. The results showed that the STL of WPC increased with an increase in sound frequency and PCC weight ratio. The improvement of sound insulation was attributed to the mass increase, sound scattering enhancement by the fillers, and PCC weight ratio. The predicted results showed similar trends to the experimental data under the same processing conditions. It was concluded that the proposed models can be used to analyze the STL of filled WPC. Larger inorganic particle size led to higher STL, but its effect was not obvious at lower frequency ranges. Predicted STL increased with increased weight ratio of wood for the whole frequency range tested.

Visible-near-infrared hyperspectral imaging was tested for its suitability for monitoring the moisture content (MC) of wood samples during natural drying. Partial least-squares regression (PLSR) prediction of MC was performed on the basis of average reflectance spectra obtained from hyperspectral images. The validation showed high prediction accuracy. The results were compared concerning the PLSR prediction of MC mapping from raw spectra and standard normal variate (SNV) treatment. SNV pretreatment leads to the best results for visualizing the MC distribution in wood. Hyperspectral imaging has a high potential for monitoring the water distribution of wood.

The present study is aimed at the detection of mechanical stresses generated in the cellulose microfibril (CMF) crystals situated in the secondary wall (S 2 ) of living cells. Green wood specimens were boiled in water to release the internal stress in the CMF by the hygrothermal softening of the lignin-hemicellulose matrix (MT). Thereafter, the changes in d 200 and d 004 lattice spacings of crystalline cellulose were observed in boiled and nonboiled samples by wide-angle X-ray diffraction. The d 200 lattice spacing increased, whereas d 004 lattice spacing decreased. The results show that a mechanical stress still remained in the CMF and the MT region in the green cell wall, even after releasing the macroscopic surface growth stresses by removal of the wood block from the living stem. The interpretation is that CMF generates tensile stress in the longitudinal direction, and surrounding MT substances generate compressive stress in the living cell wall, which compresses the CMF in the lateral direction. The results confirm the “unified hypothesis” for explaining the mechanism of growth stress generation.

Extrusion and injection moldings are standard processes for fabricating natural fiber-reinforced plastic composites, but both processes are generally not suitable for production of large-size pieces and products with high loadings of lignocelluloses. In this study, a medium-density bamboo plastic composite (BPC) was completely and successfully manufactured from bamboo fibers and polylactic acid (PLA) in the ratio of 1:1 by the flat-platen pressing process. The effects of pressing and cooling parameters on the thermomechanical properties of the BPC PLA have been investigated. The BPC PLA prepared at temperatures >180°C and cooling rates >10°C min -1 exhibited superior mechanical properties and matrix crystallinity. Under these conditions, a stronger interaction between the filler and the polymer matrix occurs and the mobility of the molecular chains at the interface decreases, which leads to a higher stiffness of the composite.

A semi-analytical prediction model of material damping in timber panels has been developed. The approach is derived from the strain energy method and the input is based on loss factors, which are intrinsic properties of the considered materials, together with other material properties and mode shape integrals, whose calculation can easily be implemented in most finite element codes. Experimental damping evaluations of particleboards, oriented strand boards, and structural laminated veneer lumber panels are presented. Fair goodness of fit between the experimental results and the prediction models – relying only on the loss factors and the mode shapes – reveals an efficient approach for the prediction of material damping in timber panels including all boundary conditions.

Formosan sweet gum ( Liquidambar formosana Hance) is a tree species endemic in Taiwan. In this study, the composition of balsam from L. formosana has been determined by several chromatographic and spectroscopic techniques. Among the 26 compounds identified, three new triterpenoids were detected, namely, 2α,3α-dihydroxyolean-12-en-28-al ( 1 ), 3α-hydroxyolean-12-en-30-ol ( 2 ), and 3α-hydroxyolean-2-oxo-12-en-28-al ( 3 ). The most abundant volatile compounds were β-caryophyllene (22.7%), α-pinene (23.3%), and β-pinene (19.6%), and the most abundant nonvolatile compounds were 3α,25-dihydroxyolean-12-en-28-oic acid ( 12 , 19.1%), oleanonic aldehyde ( 9 , 14.0%), and betulonic acid ( 15 , 13.4%). The compounds 3α,25-dihydroxyolean-12-en-28-oic acid and bornyl cinnamate were found to be inhibitory for white rot ( Lenzites betulina ) and brown rot ( Laetiporus sulphureus ) fungi.

Kraft pulps at the κ number level of 15 obtained from Acer saccharum (sugar maple) and Eucalyptus globulus prepared with and without hot water extraction (HWE) were analyzed by inverse gas chromatography (IGC) and X-ray photoelectron spectroscopy (XPS). In the case of A. saccharum pulps, the dispersive component of the surface energy ( γ s d ) at 40°C determined by IGC was 39.8 mJ m -2 (control pulp without HWE) and 36.7 mJ m -2 (HWE pulp). Eucalyptus globulus pulps resulted in γ s d values of 30.8 mJ m -2 (control) and 34.9 mJ m -2 (HWE). The higher values of γ s d for sugar maple pulps were interpreted as the influence of lower amounts of extractives or lignin at their surface, as revealed by XPS. It is also discussed why the acid-base character of the sugar maple pulp surface was slightly reduced with previous HWE, whereas, for E. globulus , it was greatly enhanced.

No abstract available.

No abstract available.