Volume 7 Issue 2

This study aims to investigate the degradation and stability of pulp treated in heterogeneous and homogeneous phases. The results showed that the homogeneous system 1-Allyl-3-Hexylimidazolium chloride (AHIMCl) ionic liquid exhibited special dissolubility for pulp samples, but showed lower thermal stability than the heterogeneous treatments by 20 wt% NaOH or 2-ethanediamine (EDA) solution. Compared with the 20 wt% NaOH solution, the 20 wt% EDA solution and AHIMCl treatments had special decrystallizing ability, and the 20 wt% EDA solution had lower reductions in the mean degree of polymerization of pulp after the treatments for 72 h at 5 oC. X-ray diffractogram (XRD) analysis showed that after the AHIMCl and 20 wt% EDA solution treatments, the 002 crystal plane size of the treated pulp samples (＜1 nm) became much lower than that of the raw pulp (5.09 nm). The diffracted intensity indicating 101 crystal planes nearly disappeared from the XRD curve of AHIMCl treated pulp samples. The X-ray photoelectron spectroscopy (XPS) analysis indicated that the significant reduction in C1s2 and O1s2 contents of the regenerated samples after the AHIMCl treatment implies that AHIMCl severely destroy the in crystalline and amorphous regions.

To make full use of bamboo resources in China and explore the foaming mechanism of bamboo powder-polypropylene (PP) foamed composites, a foamed composite of 54 wt% PP and 13 wt% HMSPP containing 33 wt% bamboo powder blends was prepared by injection moulding. Effects of chemical foaming agents (CFA) on the mechanical properties and rheological behavior of foamed composites were investigated. The mechanical measurements and ESEM test results indicated that the composite with 1% modified exothermic FA had smaller cell size and better cell distribution compared with endothermic FA. It also had better physico-mechanical properties, with a decrease of 14.2% in density and an increase of 16.8% to 40.2% in the specific tensile, bending, and notched impact strength compared with the non-foamed composite. The frequency sweep results indicated that all composites had a shear- thinning behavior, and both the modulus and complex viscosity of composite with 1% exothermic FA decreased compared with those of the non-foamed composite. The shear rate scans revealed that the non-Newtonian fluid index increased with the increase of exothermic FA content. The viscous activation energy of the modified composite with 1% exothermic FA was 46.41KJ·mol-1. This was an increase of 8.9% compared with that of the non-foamed analogue.

One of the most promising technologies for lignocellulosic biomass utilization employs ionic liquids for the conversion of isolated components into fuels, pharmaceuticals, chemicals, and composites after fractionation of lignocellulose. However, the time required for dissolution of the whole cell wall has been excessive. To explore a possible dissolution and fractionation pathway of lignocelluloses, the dissolution of holocellulose isolated from bagasse was investigated in 1-butyl-3-methylimidazolium chloride ([C4mim]Cl) assisted with ball-milling pretreatment and ultrasound irradiation. Ball milling pretreatment, ultrasonic irradiation assistance, and their combination were found to effectively improve the holocellulose dissolution in [C4mim]Cl. The effects of ultrasound power and irradiation duration on the dissolution time of ball-milled holocelluloses in [C4mim]Cl were studied. The regenerated holocelluloses were characterized with FT-IR, X-Ray, and CP/MAS 13C-NMR. It was found that there were no obvious changes of chemical structure after dissolution and regeneration of the holocellulose. The crystalline structure of cellulose was converted from cellulose I in native holocellulose to cellulose II in the regenerated holocellulose. The crystallinity decreased after the process of dissolution and regeneration assisted by ball-milling pretreatment and ultrasound irradiation.

Roll-tensioning effects on natural frequencies in circular sawblades for woodcutting were investigated. Adequate knowledge of these effects will enable a more precise and repeatable tuning of natural frequencies, which will ease manufacturing and maintenance of sawblades. With natural frequencies tuned to not create resonance under running conditions, longer running times and more accurate cutting are made easier. The aim of this study was to find the optimum, or most suitable, tensioning parameters for a series of tested circular sawblades and also to draw general conclusions. The effects of the magnitude of the roller load, number of grooves, and groove positions were tested. The magnitude of the roller load was measured by using a universal load cell. The roll-tensioning effects were evaluated by measuring the shift in natural frequencies of several vibration modes. Finite element analysis was performed to model natural frequencies. The magnitude of the roller load, number of grooves, and groove positions all affected the natural frequencies. Natural frequencies obtained with the finite element method were in good agreement with the experimental test results.

The biobleaching efficiency of xylanase and laccase enzymes was studied on kraft pulps from wood and nonwood based raw materials employed in the Indian paper industry. Treatment of these pulps with xylanase enzyme could result in improved properties, showing 2.0% ISO gain in pulp brightness and/or reducing the demand of chlorine-based bleach chemicals by up to 15% with simultaneous reduction of 20 to 25% in AOX generation in bleach effluents. Further, mill-scale trial results revealed that enzymatic prebleaching can be successfully employed with xylanases to reach the same bleach boosting efficacy. Laccase bleaching was also studied on hardwood pulp at a pH around 8.0, where most of the pulp mills in India are operating, in contrast to earlier studies on laccase enzyme bleaching, which were conducted at acidic pHs, i.e. 4.0 to 5.0. In case of laccase bleaching, interesting results were found wherein a bleach-boosting effect was observed even at pH 8.0. Further studies carried out with HOBT as mediator in comparison to the commonly used and expensive ABTS laccase mediator system (LMS) resulted in improvement of the bleaching efficiency with reduction in demand of chlorine dioxide by more than 35%. Potential for further reduction was indicated by the brightness gain, when compared with a control using the DE(p)D bleach sequence.

To investigate chemical and color changes of the polymeric constituents of black locust (Robinia pseudoacacia) wood during heat treatment, extractive-free wood flour was conditioned to 30% initial moisture content (MC) and heated for 24 h at 120 °C in either an oxygen or nitrogen atmosphere. The color change was measured using the CIELAB color system. Chemical changes of the wood components were determined by means of solid state cross-polarization/magic angle spinning 13C-nuclear magnetic resonance (CPMAS-13C-NMR), Fourier transform infrared (FTIR), diffuse reflectance UV-Vis (DRUV) spectroscopy, and elemental (CHN) analysis. The results showed that lightness (L*) decreased, while chromaticity indexes (a* and b*) and chroma (C*) increased after heat treatment.CHN analysis showed an increase in hydrogen and oxygen and a decrease in carbon content. NMR spectra confirmed the cleavage of the β-O-4 structure in the lignin, resulting in a decrease in etherified lignin units and an increase in phenolic structures. DRUV and FTIR spectra confirmed the formation of extensive conjugated structures, such as unsaturated ketones and quinones due to the cleavage of the lignin units. Formation of quinones can be attributed to heat treatment in the presence of oxygen.

The objective of this research was to study the changes in hardness and elastic modulus of wood cell walls treated with enzymes. Such changes greatly influence the properties of paper and wood composites. Two enzymes, hemicellulase and lipase, were selected for the treatment. Poplar samples (Populus euramevicana) were treated with hemicellulase, while samples of southern yellow pine (Pinus spp.) and Mongolia scotch pine (Pinus sylvestris L. var. mongolica Litv.) were treated with lipase. Mechanical properties of both treated samples were investigated by nanoindentation. The results showed some changes in the hardness and elastic modulus of the poplar cell wall treated by hemicellulase. Hardness and elastic modulus values of southern yellow pine and Mongolia scotch pine cell walls treated by lipase decreased with increasing amounts of the enzyme.

In order to improve the properties of thermomechanical pulp (TMP), the influences of the TEMPO (2,2,6,6-tetramethylpiperidyl-1-oxyl radical)-mediated oxidation on recycled TMP properties were investigated, and the impacts of recycling process on TEMPO-mediated oxidized TMP properties were studied as well. The results showed that TEMPO-mediated oxidation is an effective way to enhance the recycled TMP inter-fiber bonding dependent properties due to the introduction of carboxylic acid groups onto pulp, while the oxidation had some negative impacts on the tear index, zero span tensile index, and brightness. The oxidation-recycling (O-R) process had remarkable adverse impacts on TMP compared with the recycling-oxidation (R-O) process. The tensile, burst, tear strengths, as well as the zero-span tensile strength dropped sharply when oxidized TMP was recycled, and the physical strength properties decreased with the increasing recycling times. The opacity was improved after the O-R treatment, although the O-R treatment had an adverse impact on the pulp brightness.

Red maple, sweet gum, trembling aspen, red alder, and Eucalyptus globulus samples were pretreated with dilute sulfuric acid and green liquor before enzymatic saccharification. Substrates showed different levels of delignification and sugar recovery, depending on the applied pretreatments and the syringaldehyde/vanillin ratio (S/V). Three major conclusions were drawn in this research. First, lignin is the greatest contributor to recalcitrance of hardwood to enzymatic saccharification. Second, a high S/V ratio is a useful indicator of high delignification during a pretreatment process. Third, green liquor pretreatment is a promising pretreatment method because of a high delignification degree and sugar recovery. In addition, xylan also contributes to the recalcitrance of hardwoods toward enzymatic saccharification.

Carbohydrates that migrate to wood surfaces in sapwood during drying might influence properties such as mould susceptibility and colour. Sugars on the surface of Norway spruce boards during various heat treatments were studied. Samples (350mmx125mmx25mm) were double-stacked, facing sapwood-side outwards, and dried at 110oC to a target moisture content (MC) of 40%. Dried sub-samples (80 mm x 125 mm x 25 mm) were stacked in a similar way and further heated at 110oC and at 130oC for 12, 24, and 36 hours, respectively. Glucose, fructose, and sucrose as well as 5-hydroxymethylfurfural (HMF) and furfural in the sapwood surface layer of treated wood were analysed using HPLC (RI- and UV-detectors). Carbohydrates degraded to a lower extent at 110oC than at 130oC. Furfural and to a larger extent HMF increased with treatment period and temperature. Heat treatment led to a decrease in lightness and hue of the sapwood surface of sub-samples, while chroma increased somewhat. Furthermore, considerably faster degradation (within a few minutes) of the carbohydrates on the surface of the dried spruce boards was observed when single sub-samples were conductively hot pressed at 200oC. Treatment period and initial MC influenced the presence of the carbohydrates in wood surface as well as colour change (DEab) of the hot pressed sub-samples.