Volume 10 Issue 3

Giant timber bamboos, such as moso (Phyllostachys pubescens) and guadua (Guadua angustifolia) are potentially well-suited to the production of engineered strand-based structural composite building materials. There is no information available for guadua, but moso bamboo is known to produce good-quality, strand-based composites. However, economically viable commercial production of these composites is hindered by the lack of an efficient, automated method for converting culm stock to strands, and very little technical information is available regarding strand production and quality. In this study, moso and guadua culm characteristics and tissue re-saturation behavior likely to affect stranding were measured and compared. Strand size classification and the thickness and width distributions from stranding re-saturated moso and guadua quartered culm pieces using a CAE 6/36 single-blade disk flaker were determined. While node frequency was lower in guadua than in moso, the diaphragms and embedded wall tissue were much thicker and tougher, with strong negative effects on strand quality. When cut to a target thickness of 0.65 mm, moso bamboo produced strand thickness frequency distributions close to those found in sampled mill strands of trembling aspen, while guadua caused high wear on blades and yielded a greater proportion of excessively thick, broken, and very rough strands.

A method for direct aniline interfacial polymerization on polyamideamine-epichlorohydrin (PAE)-reinforced paper substrate is introduced in this paper. Cellulose-based papers with and without reinforcement were considered. The polyaniline (PANI)-paper composites had surface resistivity lower than 100 Ω/sq after more than 3 polymerizations. Their mechanical strength and thermal stability were analyzed by tensile tests and thermogravimetric analysis (TGA). Fourier transform infrared (FTIR) results revealed that there was strong interaction between NH groups in aniline monomers and OH groups in fibers, which did not disappear until after 3 polymerizations. Scanning electron microscopy (SEM) and field emission (FE) SEM images showed morphological differences between composites using reinforced and untreated base papers. Conductive composites made with PAE-reinforced base paper had both good thermal stability and good mechanical strength, with high conductivity and a smaller PANI amount.

Recovered papers are suitable biomass sources for conversion into sugars that can be used in bioethanol production. However, paper materials with a high lignin content have been found to be recalcitrant to enzymatic hydrolysis. To address this issue, several biomass pretreatment methods were employed to evaluate their efficiency on the conversion of newspaper with high lignin content to sugar. Autohydrolysis, a hot water treatment, was identified to adversely affect sugar conversion, presumably as a result of pore collapse under high-temperature pretreatment. Flexo ink, used in newspaper printing, had no effect on the enzymatic hydrolysis, with or without autohydrolysis. The ink was still detachable after autohydrolysis, as measured by hyperwashing. Compared to untreated newspaper, separate treatments of either mechanical refining or a non-ionic surfactant (sorbitan polyoxyethylene monooleate) improved the sugar conversion by 10% at enzyme dosages of 2 and 8 FPU/g substrate. The combination of both refining and surfactant resulted in the highest sugar conversions, i.e., 46.3%, 56.7%, and 64.1% at 2, 4, and 8 FPU/g enzyme dosages, respectively. Oxidative pretreatment (oxygen, 100 °C) marginally increased the sugar conversion, whereas alkaline and green liquor (NaCO3 and Na2S) pretreatments (at 160 °C) had either no effect or decreased the sugar conversion. Based on the results of the pretreatments, higher pretreatment temperatures of newsprint negatively impacted subsequent enzyme hydrolysis.

Extraction of aromatic substances obtained during oxidation of lignin with ionic liquids (ILs)-based molecular oxygen was investigated. It was found that virtually no aromatic substances could be directly extracted with organic solvent until water had been added to the system. The amount of extracted substances increased sharply with an increase in the molar ratio of water to ILs. The distribution constants of aromatic monomers between ILs/water and extracting solvent was obtained by Nernst partition function analysis. The constants fitted well to a second order exponential function model (ExpDec2), which indicated that the activity coefficients of reaction products between ILs and extracting solvent could be tuned by water addition. Among the seven organic solvents tested, ethyl acetate was the most effective, on account of its suitable polarity, while temperature more prominently affected extraction efficiency than time.

The application of totally chlorine-free bleaching (TCF) is well recognised for its environmental compatibility. However, its application is restricted in comparison to a chlorine-based bleaching sequence. TCF bleaching produces pulp with relatively lower brightness and strength properties. Oxygen delignification (O-stage) is commonly used as a first bleaching stage; therefore its selectivity influences TCF bleaching performance. In this study, the selectivity of the O-stage and hydrogen peroxide-reinforced O-stage (Op-stage) on tropical hardwood kraft pulp were 0.53 and 0.71, with 37.8% and 55.5% kappa number (Kn) reductions, respectively. The addition of photo pre-treatment prior to the O-stage and Op-stage improved the Kn reduction to 53.7% and 59.2%; consequently the selectivity was enhanced to 1.0 and 0.73, respectively. The Fourier transform infrared spectra showed that photo pre-treatments improved the selectivity by protecting the cellulose from carbonyl-induced degradation. This protective effect was more prominent in the O-stage than the Op-stage. However, the combination of peracetic acid and photo treatment did not further increase bleaching selectivity in either stage. In short, blue light and UV irradiation treatment with or without the prior addition of peracetic acid to ordinary or hydrogen peroxide-reinforced oxygen delignified pulp displayed a similar bleaching effect on the resultant pulp.

A phenalkamine made from the reaction of alkyl phenol from cashew nutshell liquid (CSNL) and polyamine was added at three different weight percentages (30%, 40%, and 50%) as a diglycidyl ether of bisphenol A (DGEBA) epoxy hardener. This curing agent was compared to a traditional polyamine epoxy hardener. It was observed that an increase in phenalkamine concentration resulted in considerable improvement to impact strength and elongation, which ultimately translated to better wear resistance of the cured epoxy compound. Lancaster–Ratner correlations between mechanical and wear resistance properties were found to be linear. Optical microscope observations were used to understand the wear mechanisms of the cured epoxy materials.

An alkali lignin (OL) with a weight-average molecular weight (Mw) of 11646 g/mol was used to prepare low-molecular weight lignin for resin synthesis. The low-molecular weight lignin feedstock was obtained via base-catalysed depolymerisation (BCD) treatments at different combined severity factors. Sequential fractionation of the OL and BCD-treated lignins using organic solvents with different Hildebrand solubility parameters were used to alter the homogeneity of the OL. The yield and properties of OL itself and OL and BCD-treated OL dissolved in propan-1-ol (F1), ethanol (F2), and methanol (F3) were determined. Regardless of the treatment applied, a small amount of OL was dissolved in F1 and F2. The BCD treatment did not increase the yield of F1 but did increase the yields of F2 and F3. Gel permeation chromatography (GPC) showed that the repolymerization reaction occurred in F3 for all BCD-treated OL, so these lignins were not suitable for use as feedstocks for resin production. The GPC, 13Carbon-nuclear magnetic resonance, and Fourier transform infrared spectroscopy analyses confirmed that the F3 in OL exhibited the optimum yield, molecular weight distribution, and chemical structure suitable for use as feedstocks for resin synthesis.

Acetic acid, one major inhibitor released during the hydrolysis of lignocellulosic biomass, can be utilized by the oleaginous yeast Trichosporon fermentans without glucose repression. The effect of acetic acid on the cell growth and lipid accumulation of T. fermentans under controlled pH conditions was investigated in a 5-L fermentor. Undissociated acetic acid with concentrations of 0.026, 0.052, and 0.096 g L-1 in media contributed to approximately 12-, 24-, and 48-h lag phases, respectively, indicating that undissociated acetic acid is the inhibitory molecular form. The inhibition of cell growth was correlated with undissociated acetic acid concentration. However, acetic acid had little influence on the lipid accumulation of T. fermentans at different pH conditions. The specific glucose consumption rate decreased with increasing acetic acid concentration, but the impact of acetic acid on the specific xylose consumption rate was not pronounced. In addition, the variation of pH and acetic acid concentration had no significant influence on the fatty acid composition of the lipids. Acetic acid showed more severe inhibition under low pH conditions. The reduction of intracellular pH partly explains this inhibitory effect.

In this study, wooden components torn down from ancient buildings were used as the experimental materials. With methodology based on reverse simulation testing, some artificial holes making up different proportional areas of their cross-section were chiseled and tested with a six-sensor-point stress wave testing device. The results indicated that two-dimensional analog images could be used to judge the internal defects of wooden components qualitatively but did not provide quantitative, accurate determination. By comparing and contrasting the attenuation tendency of stress wave velocities among adjacent sensor points, separated sensor points, and diagonal sensor points, the defect grade of wooden components can be classified. Six variations were chosen as discriminant factors. These were the attenuation coefficients of the stress wave velocities via three propagation paths and the relative proportions of their absolute values. The Mahalanobis distance discrimination model was adopted for the in-grade estimation of the internal defects present in the component’s cross-section. This method had high operability and no misjudgment ratio.

Experiments were carried out with a household up-draft biomass gasification stove to investigate effects of the air distribution method on the performance of the stove. The temperature distribution along the gasifier, the producer gas composition, the stove power, and the thermal efficiency were investigated. Results showed that in the temperature distribution along the gasifier height, the highest temperature was at the bottom oxidation layer of the gasifier, in the range of 950 to 1050 °C. With increasing air quantity through the burner, the time required to boil the water first decreased and then increased, whereas the stove power and thermal efficiency increased and then decreased. The best stove performance was obtained at an optimum air distribution ratio of 0.333 between burner and gasifier air (0.794×10-3 m3/s·kg). When the burner air increased, the flame length above the burner was remarkably reduced and the flame color gradually changed from yellow-red to blue. At the optimum air distribution ratio of 0.333, the flame was blue and stable. The present study provides references for developing a more efficient biomass gasification stove.