Volume 12 Issue 4

A prewashing step was used to remove ash from straw pulping solid residue (waste wheat straw, WWS) prior to pretreatment and enzymatic hydrolysis. The effects of prewashing on the effectiveness of liquid hot water pretreatment (LHWP) and dilute acid pretreatment (DAP) were investigated. Prewashing effectively removed the ash in raw WWS. However, a certain amount of polysaccharides was also removed. The decreased pH of hydrolyzate after pretreatment suggested that both the prewashing and DAP could destroy the buffering effect of ash and thus improve the pretreatment efficiency. Consequently, the highest enzymatic hydrolysis yields of 79.4% and 76.1% could be obtained for LHWP and DAP, respectively. In addition, the LHWP resulted in the highest sugar recovery of 84.4% at 180 °C, and a sugar recovery of 86.8% was also reached by DAP at 160 °C. LHWP combined with prewashing strongly facilitated the enzymatic digestibility of WWS pretreated at 180 °C. However, for pretreatment at low temperature, DAP was more suitable.

To reduce the formaldehyde emissions of plywood used in furniture and interior decorations, new plywood composites made from surface modified veneers and polyvinyl chloride films were developed. These films were used as formaldehyde-free adhesives, and the veneer surfaces were modified with 3-aminopropyl(triethoxy)silane to enhance the compatibility with the films. Hot-pressing of composites was optimized using a response surface methodology. The effects of 3-aminopropyl(triethoxy)silane modification on various properties of veneers and composites were studied by Fourier transform infrared spectroscopy, contact angle, physico-mechanical, scanning electron microscope, dynamic mechanical, and thermogravimetric analyses. The optimum hot-pressing process for the composites was 183 °C (temperature), 74 s/mm (duration), and 312.5 g/m2 (adhesive). The modification with 3-aminopropyl(triethoxy)silane enhanced the hydrophobicity of veneer surfaces and improved the interfacial adhesion and physico-mechanical properties of composites. Adding 3% 3-aminopropyl(triethoxy)silane resulted in approximately 40% of decrease in water adsorption of composites and 30% increase in wet shear strength. The 3-aminopropyl(triethoxy)silane modification also improved the thermal stability of composites. The physico-mechanical properties of both the unmodified and modified composites met the requirements in Chinese national standard GB/T 9846 (2015) for the water-resistant plywood, indicating the potential of proposed composites as new building materials.

Deep drawing of paperboard with rigid tools and immediate compression has only a small presence in the market for secondary packaging solutions due to a lack of understanding of the physical relations that occur during the forming process. As with other processes that deal with interactions between two solids in contact, the control of the factors that affect friction is important due to friction’s impact on runnability and process reliability. A new friction measurement device was developed to evaluate the factors influencing the friction behavior of paperboard such as under the specific conditions of the deep drawing process, which differ from the standard friction testing methods. The tribocharging of the contacting surfaces, generated during sliding friction, was determined to be a major influence on the dynamic coefficient of friction between paperboard and metal. The same effect could be examined during the deep drawing process. With increased contact temperature due to the heating of the tools, the coefficient of friction decreased significantly, but it remained constant after reaching a certain charging state after several repetitions. Consequently, to avoid ruptures of the wall during the forming process, tools that are in contact with the paperboard should be heated.

The quality of press-formed paperboard trays and its effect on the leakproof heat-sealability of the lidding film is known to depend on the quality of the sealed trays and the parameters of the sealing process. In this study, the elevation of the sealing pressure and its effect on the leak-proof heat-sealing of press-formed trays with reduced surface quality were investigated. Trays with varying quality were manufactured and heat-sealed with a lidding film, using three different sealing pressures. The quality of the sealed trays was evaluated using oxygen content measurements, leak detection by a coloring solution, and microscopic analysis. The results showed that using a higher, elevated pressure resulted in a lower oxygen content in the packages during the analysis. The results also showed that even a high sealing pressure was not enough to achieve a leakproof seal if the quality of the sealed trays was not in a satisfactory level, for example as a result from a low forming force.

The effect of fibre length on the yield stress of recycled old corrugated containers (OCC) pulp fibre suspensions was investigated. Two types of OCC pulps were divided into four fractions based on the fibre length with a Bauer-McNett classifier. The yield stress of each fraction was measured using the shear stress ramp method at pulp consistency ranging from 0.5% to 2.5% (w/v). The results showed that both pulp consistency and fibre length had significant effects on the yield stress of OCC pulp suspensions, and the yield stress was greater with increasing fibre length and pulp consistency. Moreover, the effect of consistency in OCC pulp suspension with long fibres on the yield stress was stronger than in the slurry with short fibres.

A near infrared (NIR) spectroscopy-based method for predicting yields and lignin contents of differently pre-treated silver/white birch (Betula pendula/B. pubescens) and Scots pine (Pinus sylvestris) chips was developed. The approach was to create multivariate calibration models from the NIR data by the partial least squares (PLS) method. Both parameters are important factors when adjusting adequate conditions for pre-treatments either with hot-water (HW) as such and slightly acidified HW (collectively referred to as autohydrolysis) or dilute alkaline aqueous solutions prior to alkaline pulping. Pre-treatment conditions were varied with respect to temperature (130 °C and 150 °C) and treatment time (from 30 min to 120 min). In the case of alkaline pre-treatments, the NaOH charge was 1% to 8% NaOH on wood dry solids (DS). The yields varied in the range 81.2% to 99.3% (in autohydrolyses) and 83.5% to 97.9% (in alkaline pre-treatments). High correlation coefficients and low prediction errors in relation to conventional yield and lignin content data clearly indicated the suitability of NIR spectroscopy combined with the multivariate modeling as an effective and fast tool for this purpose. This technique also showed promising possibilities for developing practical process control methods to follow such pre-treatments.

Silver-loaded thermo-sensitive nanogels (STSNGs), having a pH value of 6.8, were used as an anti-fungal agent at ambient temperature. To determine the optimal impregnation process, bamboo strips were infused with STSNG by air- and vacuum-pressurization. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction were employed to characterize the properties and morphology of the resulting impregnated bamboo strips. The results showed that the loading dosage of bamboo strips increased with either prolonged impregnation treatment time, increasing hybrid nanogels concentration, or increasing the intensity of vacuum and pressure. Vacuum-pressurized impregnation remarkably improved the dosage of the hybrid nanogels in the bamboo strips. An increase in the loading dosage resulted in an increase in Ag content. The optimum parameters of impregnation treatment were as follows: 90 min impregnation treatment time, 0.90 wt.% concentration, and 0.5 MPa applied pressure. SEM observations revealed that the STSNGs were successfully saturated in bamboo cell cavities or covered on the cell walls. The results of the mildew proof test showed that the STSNGs had a good anti-mildew effect.

Glucose and mannose, the major structural units found in softwood hemicelluloses, were used to produce 5-hydroxymethylfurfural (HMF) in the ionic liquid 1-butyl-3-methylimidazolium chloride, in the presence of a commercial zeolite (which acted as an acidic catalyst), and in the presence or absence of co-catalysts. Experiments were performed under diverse operational conditions, and the reaction kinetics were interpreted by a mechanism involving three major reactions (non-productive substrate conversion, HMF generation, and HMF decomposition). Activation energies were determined for the best reaction medium.

A bio-inspired approach to coating polydopamine (PDA) onto bamboo fiber (BF) was developed to enhance the poor interfacial bonding of BF/polybutylene succinate (PBS) biocomposites. The macroscopic features, functional groups, nanoscale topography, and crystallinity of the PDA-coated BF (D-BF) were investigated with digital photography, Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), and X-ray diffraction (XRD), respectively. The effects of the PDA loading rate on the performance of the D-BF/PBS biocomposites were also evaluated through the mechanical properties tests, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). Treating BF with an optimum concentration of dopamine (DOPA) decreased the polarity of the bamboo fiber, while maintaining the crystal structure of the cellulose. The thermal stability, mechanical properties, and storage modulus of the D-BF/PBS biocomposites were noticeably enhanced because of the good interfacial compatibility. Moreover, the glass transition temperature (Tg) and crystallinity of the biocomposites increased with higher DOPA loading rates. The best properties were observed with a DOPA concentration of 1.0 mg/mL. These findings exhibited the feasibility for the application of PDA in the biomass fiber-reinforced biodegradable polymer composites industry.

The ellipticity of hardwood logs is most often observed and measured from either end of a log. However, due to the nature of hardwood tree growth and bucking practices, the assessment of ellipticity in this manner may not be accurate. Trees grown on hillsides often develop supporting wood that gives the first few feet of the log butt a significant degree of ellipticity, while the rest of the log may be more circular. Good log bucking methods dictate that a log be bucked near a fork or a large knot, creating a higher-valued lower log and a jump cut or a lower-valued upper log. This practice and the additional supporting (buttress) wood below the knot can make the upper end of a log exhibit ellipticity. In this study, 703 hardwood logs from Appalachian forests were scanned using a high-resolution laser scanner, and the ellipticity and the angle of the greater axis was recorded for every foot along each log. Approximately one-third of the logs exhibited moderate to severe eccentricity on the small end. However, most logs (99%) did not exhibit significant ellipticity along the entire length. Furthermore, the mean length of the elliptical zone for all species was 3.3 feet.