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The process named 'sulfite pretreatment to overcome recalcitrance of lignocellulose' (SPORL) is designed for the digestion of softwoods within the framework of the biorefinery concept. 'Hot water extraction (HWE)' is an environmentally benign and low-cost pretreatment, which only needs water as a reagent. In the present study, HWE has been investigated as a pre-process prior to SPORL with Douglas fir as feedstock. The SPORL parameters, namely, temperature and treatment time, were in the range 135-155°C and 40-120 min, respectively, while the sulfuric acid concentration was 0.2-0.4% (v/v). The aim was to maximize the enzymatic digestibility of the treated wood. The severity of SPORL at different pretreatment conditions was characterized by the combined severity factor (CSF). The HWE pre-process led to a two-fold increase in specific surface area of the substrate. More hemicellulosic-derived simple sugars were dissolved in the spent liquor (SL) as the CSF increased from 1.23 to 1.82. A maximum enzymatic digestibility of 64.3% was attained when SPORL was conducted at 155°C for 120 min with a sulfuric acid concentration of 0.4% (v/v). A considerably high enzymatic digestibility (~55-60%) is still achievable by incorporating HWE prior to SPORL, even if the SPORL severity is reduced, namely to a lower temperature (145°C), a shorter time (80 min), and a lower acid volume (0.3% v/v). [ABSTRACT FROM AUTHOR]

Hot water extraction (HWE) partially removes hemicelluloses from wood while leaving the majority of the lignin and cellulose; however, the lignin partially migrates to the inner surfaces of the cell wall where it can be deposited as a layer that is sometimes visible as droplets. This lignin-rich material was isolated via Soxhlet extraction with dichloromethane to investigate its rheological behavior in blends with high-density polyethylene (HDPE), a common material in wood plastic composites (WPCs). Pyrolysis gas-chromatography/mass spectrometry (Py-GC/MS) and electrospray ion mass spectrometry (ESI/MS) confirmed that the isolated material is constituted mainly of low-molecular-weight lignin oligomers. The blends of HDPE/isolated lignin, in varying ratios, were tested by means of dynamic rheology. A 'shoulder' was found in plots 'shear storage moduli (G′) vs. frequency sweep' and a shift of the terminal zone to lower frequencies was observed. Apparently, this shoulder is caused by the elastic contribution of the interfacial tension between the blend components. The rheology of WPCs produced from HWE wood and HDPE shows a similar shoulder in G′ plots, suggesting that the HDPE/lignin blends are in part responsible for the shape of the G′ curves. [ABSTRACT FROM AUTHOR]

The affinity of particleboard (PB) to water is one of the main limitations for using PB in moisture-rich environments. PB dimensional stability and durability can be improved by reducing the available hydroxyl groups in wood through hemicellulose removal, for example, by hot water extraction (HWE), which increases wood resistance to moisture uptake. The resulting liquid fraction from HWE is rich in hemicelluloses and can be used for chemicals and fuels, and the solid fraction is less hydrophilic. The objective of this study was to investigate the effects of HWE of softwood chips (conducted at 160°C and 90 min) and hardwood chips (160°C and 120 min) on the properties of PB panels. HWE increased compressibility and reduced springback by 34% and 44% for pine and maple chips, respectively, which positively impacted the PB properties. Water absorption of pine PB panels was lowered by 35% and that of maple PB panels by 30%, while reduction of thickness swelling was lowered by 39% for pine PB and 56% for maple PB after 24 h of immersion in water. The mechanical properties were not significantly affected. [ABSTRACT FROM AUTHOR]

Undebarked ponderosa pine chips were treated by hot water extraction to modify the chemical composition. In the treated pine (TP), the mass was reduced by approximately 20%, and the extract was composed mainly of degradation products of hemicelluloses. Wood flour produced from TP and unextracted chips (untreated pine, UP) was blended with high-density polyethylene (HDPE) and polypropylene (PP) and was extruded into wood plastic composites (WPCs). Formulations for WPCs consisted of 58% pine, 32% plastic, and 10% other additives. WPC based on HDPE+TP and PP+TP absorbed 46-45% less water than did WPC based on HDPE+UP and PP+UP, respectively. Thickness swelling was reduced by 45-59%, respectively, after 2520 h of immersion. The diffusion constant decreased by approximately 36%. Evaluation of mechanical properties in flexure and tension mode indicated improvements in TP-WPC properties, although the data were not statistically significant in all cases. Results showed that debarking of ponderosa pine is not required for WPC production. [ABSTRACT FROM AUTHOR]