Research Articles

In order to decrease the viscosity and improve the wet shear strength of soybean meal (SM) adhesive, in this study, SM adhesive, enzyme-treated SM adhesive(ESM), and the ESM grafted GMA (ESM-g-GMA) adhesive were prepared . The properties of these adhesives were characterized by rheological measurement, mechanical performance testing, Fourier transform infrared spectroscopy (FTIR), and thermogravistric analysis (TGA ). The results indicated that the apparent viscosity of the adhesives decreased due to the enzymatic treatment and the presence of GMA. The wet shear strength of the plywood panels bonded with ESM-g-GMA adhesive was significantly improved from 0.45 MPa to 1.05 MPa, which met the interior plywood requirement (≥0.7 MPa) of the China National Standard. This study also investigated the pot life of the ESM-g-GMA adhesive and the impact of hot pressing. The change in wet shear strength was not obvious within 24 h. The optimum hot press temperature and time were 150 oC and 6 min, respectively. FTIR showed that GMA was successfully grafted onto the ESM adhesive. TGA indicated that the peak degradation temperature of the ESM-g-GMA adhesive was higher than that of the SM adhesive due to the cross-linking reaction that created the macromolecular dense structure between the ESM adhesive and the GMA monomer.

To increase the water resistance and reduce the viscosity of soybean meal (SM)-based non-formaldehyde wood adhesives, polyethyleneglycol diacrylate (PEGDA) used as crosslinker and viscosity reducer was introduced into the SM adhesive system. The apparent viscosity was evaluated by rheological measurements; gel content and water absorption of adhesives, the wet shear strength of plywood bonded with these modified adhesives were tested to evaluate their water resistance. In addition, the crosslink structures of modified adhesives were characterized by Fourier transform infrared (FTIR) spectroscopy and solid-state 13C NMR analysis. The results indicated that all of the SM adhesives were pseudoplastic fluids with the property of shear-thinning. The viscosity of modified SM adhesives effectively decreased by 35% compared with the addition of PEGDA, and the wet shear strength of their bonded plywood increased; the wet shear strength of plywood bonded with 4% PEGDA-modified SM adhesive increased 114.2% compared to SM adhesive. FTIR spectroscopy and solid-state 13C NMR analysis demonstrated that the crosslinking reaction of the PEGDA occurred successfully during the curing process of PEGDA modified SM adhesive, and no crosslinking reaction between the PEGDA and soy meal adhesive appeared to have occurred. Interpenetrating networks (IPNs) might be formed between the cured PEGDA and SM adhesive system.

A combination of steam explosion (SE) and alkaline peroxide (AP) used to pretreat bamboo was investigated. Steam explosion at 224 °C for 4 min was applied to bamboo, and the pretreated bamboo was delignified by alkaline peroxide. Enzymatic hydrolysis was compared in the pretreated samples. Steam pretreatment led to remarkable hemicellulose solubilization (63.2%). Lignin solubilization (93.1%) was achieved by alkaline peroxide treatment of steam-pretreated bamboo at 80 °C for 1 h in 0.88% (v/v) H2O2, whereas only 33.4% of lignin was solubilized when using raw bamboo. Pretreatment methods resulted in a low degree of polymerization and increased hydrolysis of cellulose. A maximum glucose yield of 90.5% was achieved with a combined steam explosion and alkaline peroxide pretreatment. The surface structure of treated bamboo and the adsorption of enzyme on the substrate were characterized by X-ray photoelectron spectroscopy. Delignification decreased enzyme adsorption and increased enzymatic conversion. SEM analyses indicated that SE-AP pretreatment disrupted lignin networks and exposed crystalline cellulose in bamboo more effectively than SE or AP pretreatment alone.

Pretreatment of forest residues using N-methylmorpholine-N-oxide(NMMO or NMO) prior to anaerobic digestion was investigated, where the effects of particle size, NMMO concentration, and pretreatment time were the primary focus. The pretreatments were carried out on forest residues; with different particle sizes of 2, 4 and 8 mm, at 120 °C for 3, 7, and 15 h in two different modes of NMMO-treatment: dissolution by 85% NMMO and swelling without dissolution using 75% NMMO solution in water. The pretreatment process led to minor changes in the composition of the forest residues. The best improvement in methane yield of the forest residues was achieved by pretreatment using 85% NMMO for 15 h at 120 °C. This treatment resulted in 0.17 Nm3/kg VS methane yield, which corresponds to 83% of the expected theoretical yield of carbohydrates present in the material. Additionally, the accumulated methane yield and the rate of the methane production were highly affected by the amounts of remaining NMMO when it was not well separated during the washing and filtration steps after the treatment. The presence of concentrations even as low as 0.008% NMMO resulted in a decrease in the final methane yield by 45%, while the presence of 1% of this solvent in the digester completely terminated the anaerobic digestion process.

The effects of refining history and recycling times of NSSC pulp as a representative of semi-chemical pulps were studied. The results indicated that NSSC behaved as would be expected for a chemical pulp in all aspects. In fact, increasing the recycling cycles decreased the apparent density, tensile index, burst index, tear index, water retention value (WRV), and increased the hornification. In the current research, 400 mL CSF was judged to be the most suitable treatment among the refining levels considered. In the case of virgin pulp 400 mL CSF yielded better results than 500 mL CSF in all aspects (apparent density, tensile index, burst index, tear index, WRV and hornification). Also, there was not much difference with 300 mL CSF in these properties. Generally, a refining history of 400 mL CSF gave rise to the least negative influence on different properties compared to 500 and 300 mL CSF in 1st, 2nd, and 3rd recycling cycles of NSSC.

This study explored the effect of processing parameters on surface roughness as a result of aesthetic designs processed on walnut, chestnut, and beech wood edge-glued panels (EGPs) by CNC (computer numerical control) router. To accomplish this, the average roughness value (Ra) on an engraved surface in a Ying-Yang design treated on the material was measured. Using analysis of variance (ANOVA), the feed rate, spindle speed, step-over, and axial depth of cut factors; surface roughness factors; and the interactions between these factors were found to form significant differences at the level of 95%. At the end of the study, the Ra value was lower in walnut and beech EGPs (3.423 μm and 4.316 μm, respectively) and higher in chestnut EGPs (5.005 μm).

The use of mineral fillers in cellulosic paper products can result in cost/energy savings and improvement of paper properties. However, the increase in filler addition levels is hampered by the negative impact of fillers on paper strength, poor filler retention, etc. As an attempt to improve the use of fillers in papermaking, filler modification with the combination of cationic starch and carboxymethyl cellulose was preliminarily explored in this mini-study. This concept was compared with filler modification with either cationic starch or carboxymethyl cellulose. The combination of cationic starch with carboxymethyl cellulose resulted in improved attachment of the starch to the filler, possibly suggesting the in-situ formation of polymer complexes with lower solubility than starch. With respect to filler retention, tensile strength, brightness, and opacity of the filled paper, the combined use of cationic starch and carboxymethyl cellulose resulted in a modified filler material with modestly better performance, in comparison to filler modification with either cationic starch or carboxymethyl cellulose. The combined use of a cationic polymer and an anionic polymer to modify fillers may provide an alternative approach to improving the use of mineral fillers in the paper industry.

Biochars produced from thermochemical conversions of biomass were evaluated by temperature programmed oxidation (TPO). This technique, used to characterize carbon deposits on petroleum cracking catalysts, provides information on the oxidative stability of carbonaceous solids, where higher temperature reactivity indicates greater structural order, an important property for biochar applications. Differences between TPO profiles of biochars generated by fast pyrolysis of soy straw, barley straw, switchgrass, bamboo, and various woods demonstrated that the oxidative stabilities of the biochars are dependent on the starting biomass. Biochars from softwood and hardwood feedstocks were also processed by torrefaction and gasification to assess the impact of the thermoprocessing method on the TPO data. Results from these TPO analyses showed that the biochars produced under higher temperature conditions afford biochars that are more oxidation resistant. Biochars produced from pine wood (softwood) were consistently more resistant to oxidation compared to their hardwood counterparts. This exploratory study represents the first application of TPO to biochars.

To better understand how moisture content (MC) affects the longitudinal compressive mechanical properties of bamboo, mechanical tests on both the macroscopic and cellular levels were performed on Moso bamboo (Phyllostachys pubescens Mazei ex H. de Lebaie) at different MCs. At the macroscopic level, the compressive modulus of elasticity (CMOE) was determined using a common mechanical tester, while the indentation modulus of elasticity (EIT) and the hardness (HIT) of the bamboo fiber cell walls were obtained using nanoindentation. The results showed that CMOE, EIT, and HIT were all negatively correlated with the change in MC below the fiber saturation point (FSP) with strong linear relationships. However, the CMOE was found to be more sensitive to a change in MC than was EIT, which indicated that the bamboo was more sensitive to MC at the macro level than at the cellular level, at least in terms of longitudinal compression stiffness. Moreover, EIT was found to be much less sensitive to a change in MC than was HIT, which may explain why the longitudinal compression strength of bamboo was much more sensitive to changes in MC than was the compression modulus of elasticity on the macro scale.

The feasibility of the combination of fungal with mild acid pretreatments of Glycyrrhiza uralensis residue (GUR) for enzymatic hydrolysis and oil production was studied. Combined pretreatment with Phanerochaete chrysosporium and 2.5% sulfuric acid was shown to be more effective than the acid-only pretreatment. Subsequently, the residue obtained from acid hydrolysis was subjected to enzymatic hydrolysis to generate fermentable sugars for oil production by Chlorella protothecoides. The reducing sugar yield of enzyme hydrolysate from co-treated GUR was 1.08- to 1.71-fold higher than that obtained from acid-treated GUR under the same conditions. The highest cell dry and oil yield from co-treated GUR reached 4.16 and 1.66 g/L dry weight, respectively, values which were 2.1- and 3.32-fold higher than those using glucose as a carbon source. This study suggested that combined pretreatment with P. chrysosporium and 2.5% sulfuric acid is an effective strategy for enhancing enzymatic hydrolysis and microalgal oil production from GUR.