Research Articles

In this work, a pressure-sensitive adhesive (PSA) was used as the model substance for secondary stickies. The dissolved and colloidal substances (DCS) prepared from bleached chemithermomechanical pulp (BCTMP) and the effects of pectinase treatment on the stickies deposition were evaluated. The results showed that the addition of DCS lowered the efficiency of cationic polymers and aggravated the deposition of stickies. As a major component of anionic DCS, polygalacturonic acids can be effectively degraded during pectinase treatment. Therefore, the efficiency of cationic polymers improved, and subsequently they were able to fix the destabilized sticky particles on the fibers, which led to the decrease of stickies deposition. However, the pectinase treatment of DCS insignificantly affected stickies deposition in absence of cationic polymers when the stickies deposition was caused by calcium ions.

Heat treatment may result in variation of wood equilibrium moisture content (EMC). During this study, tauari (Couratari oblongifolia), ash (Fraxinus excelsior), and oak (Quercus rubra) woods were heat-treated at 190, 200, and 210ºC for 3 hours and then put into a conditioning chamber with a temperature from 30 to 75ºC and a relative humidity from 50 to 90%. The isothermal moisture adsorption curve was subsequently analyzed. Results indicated that the EMC of heat-treated wood was reduced by 23.4 to 37.4% compared to non-treated wood, but the EMC difference at different heat-treated temperatures for three hardwoods was quite small and the EMC of heat-treated wood was inversely proportional to their dry density.

Hybrid composites of polyethylene/wood flour/nanoclay with different concentrations of nanoclay were fabricated using melt compounding followed by injection molding. Composites were weathered in a xenon-arc type accelerated weathering apparatus for 2000 h. Physical properties of the composites were evaluated by colorimetery and water absorption before and after weathering. Changes in surface chemistry were monitored using spectroscopic techniques. The results indicated that water absorption of the composites increased after weathering, but nanoclay can reduce the intensity of weathering to some extent by decreasing water absorption. Weathering increased the degree of color change and lightness of the samples; however, the lightness of the samples containing nanoclay was less than that of neat wood-plastic composites. Fourier transform infrared spectroscopy revealed a lower carbonyl index of composites containing nanoclay. X-ray diffraction patterns revealed that the nanocomposites formed were intercalated. The order of intercalation for samples containing 2 wt% nanoclay was higher than that of 4 wt% at the same maleic anhydride grafted polyethylene content, due to some agglomeration of the nanoclay.

Effects of heat treatment on the physical properties of heartwood and sapwood of Cedrus libani A. Richard, such as density, equilibrium moisture content, swelling, and fiber saturation point were investigated. Heartwood and sapwood samples were treated at 140, 160, 180, 200, and 220°C for 3 h. After heat treatment, the physical properties of the samples of wood were determined according to Turkish standards. The results showed that mass loss increased and physical properties decreased as the treatment temperature increased. As the treatment temperature was increased, the mass of the heartwood decreased more than that of the sapwood, which may be due to the fact that the heartwood had greater extractives content. Conversely, even though the mass of the heartwood decreased more than the mass of the sapwood at the treatment temperature of 220°C, its physical properties, such as equilibrium moisture content, swelling, and fiber saturation point, decreased less than those of the sapwood.

Pyrolysis characteristics and mechanism of tobacco stem were studied by pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS), thermogravimetric analyzer coupled with Fourier transform infrared spectrometry, and mass spectrometry (TG-FTIR and TG-MS) techniques. The composition of evolved volatiles from fast pyrolysis of tobacco stem was determined by Py-GC/MS analysis, and the evolution patterns of the major products were investigated by TG-FTIR and TG-MS. Py-GC/MS data indicated that furfural and phenol were the major products in low temperature pyrolysis, and these were generated from depolymerization of cellulose. Indene and naphthalene were the major products in high temperature pyrolysis. TG-FTIR and TG-MS results showed that CO, CO2, phenols, aldehydes, and ketones were released between 167ºC and 500ºC; at temperatures >500ºC, CO and CO2 were the main gaseous products.

Bending properties of Turkish red pine (Pinus brutia Ten.) lumber pieces were predicted using the stress wave method. The lumber samples were taken from 30- to 80-year-old red pine trees harvested from a southwest site in Turkey. MTG timber grader was utilized to predict modulus of elasticity (MOE) and modulus of rupture (MOR) values of lumbers with 40 mm x 90 mm in cross section and 3 meters in length. Static MOE and MOR values of the lumber pieces were determined using a three-point bending test. The coefficient of determination between measured and predicted MOEs was 0.84 and that between dynamic MOE and bending strength was 0.69. However, the coefficient of determination between bending MOE and strength was only 0.45. It seems that dynamic MOE has better prediction capability for bending strength than static MOE. Effects of some variables such as log and visual grades on dynamic MOE values were also determined statistically. Natural frequency of the lumbers showed far more significant effects than other variables. It is apparent that the stress wave method has the potential to predict the bending properties of Turkish red pine lumber.

By applying increasing amounts of ozone (Z stage bleaching) on eucalyptus oxygen-delignified pulps, it was observed that both lignin and hexenuronic acids (HexA) are attacked early during the treatment. While the HexA were progressively removed, however, the oxidized lignin tended to stay in the pulp. An acidic stage (A stage) at pH 3 and a temperature of 90 to 95°C removed a high proportion of the HexA, which eventually reduced the ozone requirement. In spite of the negative impact of the A stage on the DP of cellulose, totally chlorine-free sequences containing A led to pulps of higher viscosity. Increasing the temperature in A to 120°C did not seem to have an effect other than increasing the rate of the hydrolysis reactions. A very efficient metal removal was observed when a chelating agent was added in A (AQ). Some trials showed that splitting the Z stage in a ZEZE-like process (E for alkaline extraction) minimized the impact on pulp viscosity, and that AQPZE-like sequences can reach a quality comparable to some commercial elemental chlorine-free (ECF) pulps.

This study was undertaken to isolate ligninase-producing white-rot fungi for use in the extraction of fibre from pineapple leaf agriwaste. Fifteen fungal strains were isolated from dead tree trunks and leaf litter. Ligninolytic enzymes (lignin peroxidase (LiP), manganese peroxidase (MnP), and laccase (Lac)), were produced by solid-state fermentation (SSF) using pineapple leaves as the substrate. Of the isolated strains, the one showing maximum production of ligninolytic enzymes was identified to be Ganoderma lucidum by 18S ribotyping. Single parameter optimization and response surface methodology of different process variables were carried out for enzyme production. Incubation period, agitation, and Tween-80 were identified to be the most significant variables through Plackett-Burman design. These variables were further optimized by Box-Behnken design. The overall maximum yield of ligninolytic enzymes was achieved by experimental analysis under these optimal conditions. Quantitative lignin analysis of pineapple leaves by Klason lignin method showed significant degradation of lignin by Ganoderma lucidum under SSF.

Samples of Chinese fir were treated with either low-molecular-weight or commercial phenol-formaldehyde (PF) resins. The macro- and micromechanical properties of the treated and untreated samples were determined. The average longitudinal tensile modulus of elasticity (MOE) was 30.88% larger for the samples treated with the low-molecular-weight PF resin than it was for the untreated samples. The average MOE of the samples treated with the commercial PF resin was 29.84% less than that of the untreated samples. The micromechanical properties of the samples were investigated through nanoindentation studies. For the samples modified with low-molecular-weight PF resin, the values of average MOE and hardness were 32.94 and 32.93%, respectively, greater than those of the untreated samples. In contrast, the average MOE and hardness values were 11.99 and 18.14%, respectively, greater for the samples modified with commercial PF resin compared to the untreated samples. It could be inferred that the low-molecular-weight PF resin was able to diffuse into the nanopores in the S2 layer of the tracheid cell wall of the Chinese fir, thereby improving its macromechanical properties. Modification with low-molecular-weight PF resin was an effective way to enhance the longitudinal macromechanical properties of wood from the Chinese fir.

The objective of this study was to investigate the physical properties, including density, moisture content, thickness swelling, and water absorption, in addition to the mechanical properties such as modulus of rupture, modulus of elasticity, and internal bond strength of experimental panels that were made from rubberwood particles using oil palm starch modified with epichlorohydrin as a binder. The samples were also examined using X-ray diffractometry, scanning electron microscopy, thermogravimetric analysis, and differential scanning calorimetry. The panel properties were compared with the properties of panels manufactured using native oil palm starch. The properties of starch and starch adhesives were also investigated. The panels were produced based on 0.60 g/cm3 and 0.80 g/cm3 target densities and two press times of 15 and 20 min. The results showed that the 0.80 g/cm3 panels manufactured using modified oil palm starch and with 15 min of press time had better properties than did the others. However, a lower thickness swelling value was found for panels with density 0.60 g/cm3 and with 15 min of press time. Based on the results in this study, it can be concluded that the use of oil palm starch modified with epichlorohydrin as a binder has the potential to be used as a green adhesive in commercial applications.