Volume 14 Issue 3

With the increased awareness of thermal insulation of buildings, the knowledge of thermal conductivity of non-structural materials applied for roughing, cladding or flooring has become more important. The objective of this study was to investigate the thermal conductivity of 31 different wood species originated from the region of Izmir in Turkey. Thermal conductivity of air dried boards was determined in accordance to ASTM 5334 standard which measures this property on the interior of wood rather than on the surface. Thermal conductivity varied from 0.090 to 0.197 W/mK. The highest thermal conductivity was obtained for oak and the lowest for Canadian poplar. A linear relation was obtained between wood density and thermal conductivity.

There is significant interest in preparing packaging film from sustainable polysaccharides, especially hemicellulose (HC). Hemicellulose isolated from wheat straw tends to aggregate into dissolved particles in aqueous solutions and to form poor films. When methylcellulose (MC) was added into the HC solution, HC and MC formed a HC-MC complex. With increased MC content, the size of the HC-MC complex decreased, and its surface charge increased at the same time. When 35 wt% MC was added into the HC, a continuous HC-MC film formed in the layer structure. The HC-MC film with 75 wt% MC showed a more compact layer structure compared with other films. The tensile strengths of the HC-MC film increased with the MC addition. When MC was added to 75 wt%, the tensile strengths of the HC-MC film reached their maximum values, which were higher than that of MC film. This high film strength suggested these HC-MC composite films have potential applications in packaging material.

Various flours were added as fillers for urea-formaldehyde (UF) resin, and effects on the rheological behavior and the curing properties of the resin were evaluated. The plywood properties such as bonding quality, bending strength, modulus of elasticity, and formaldehyde-release were tested. Five types of flours were used, i.e., rye flour, hemp flour, coconut flour, rice flour, and pumpkin flour. The type of flour had a major influence on the properties of resin mixture such as gel time, solid content, and viscosity. The use of rye and pumpkin flour resulted in a longer gelling time, and the adhesive mixture filled with rice flour did not attain the desired viscosity value needed for the production of plywood. The best mechanical properties and bonding quality were achieved by addition of pumpkin flour. However, the bonding quality of plywood glued with an adhesive filled with every other flour retained good values exceeding 1 N/mm2 as required by the standard EN 314-2 (1993). The use of hemp flour as a filler for UF resin led to a substantial decrease of free formaldehyde content.

This study examined the manufacture of flat-pressed wood plastic composites (WPC) using rape chips glued with polymeric diphenylmethane diisocyanate (pMDI). Manufactured boards were of 5-ply type, with 30% polyethylene (PE) content in individual layers. The following properties were assessed: modulus of rupture (MOR); modulus of elasticity (MOE); internal bonding strength (IB); thickness swelling (TS) after 24 hours; water absorption (WA); and noise reduction effectiveness. The tests revealed better physical and mechanical properties of polymer-particle boards than similar polymer and rape boards. It was also demonstrated that a change in mechanical properties of polymer and lignin-cellulose boards is strongly associated with polymer location in individual board layers, and that greater porosity of wood material ensures better polymer anchoring in its structure, when compared with rape straw particles.

Composting technology comprising hyperthermophilic pretreatment (at ≥85 °C for 2 to 4 h, HTPRT) and aerobic composting was adopted to accelerate organic matter transformation and enhance nitrogen retention in chicken manure composting. The differences in physio-chemical parameters, successions, and metabolism functions of the bacterial community between HTPRT (85 °C, 4 h) and conventional composting (CK) were compared. The HTPRT composting system reached maturity 18 days in advance of CK. The HTPRT piles showed a lower maximum N loss (27.1% vs. 39.0%). The bacterial structure in the HTPRT system differed remarkably from that in CK. Ureibacillus (22.7%) and Ammoniibacillus (14.1%) were the most predominant species in the thermophilic phase of HTPRT pile, while the curing phase was dominated by Thermobifida (12.8%) and Saccharomonospora (11.8%). The authors’ results suggest that HTPRT improved the physical properties of the feedstock by reducing the bulk density, which favored microbiological activity, and thus improving composting efficiency.

Bifunctional cellulases with β-glucosidase (Bgl1), exoglucanase (Exo5), and carbohydrate-binding modules (CBMs) from Caldicellulosiruptor saccharolyticus were fused to yield several recombinant plasmids, Bgl1-CBM-Exo5, Bgl1-2CBM-Exo5, and Bgl1-3CBM-Exo5. The fused enzymes possessed both β-glucosidase and exoglucanase activities and were used to improve the degradation efficiency of lignocellulosic biomass. The optimal temperature of Bgl1-3CBM-Exo5 was 70 °C, which was the same as Bgl1, and the optimal temperature of the other two enzymes was 80 °C, which was the same as Exo5. The optimal pH of fused enzymes was 4 to 5, the same as Exo5, but the optimal pH of Bgl1 was 5.5. Compared with Bgl1-CBM-Exo5 and Bgl1-2CBM-Exo5, the hydrolysis efficiency of Bgl1-3CBM-Exo5 on sodium carboxymethyl cellulose (CMC-Na) was increased by 67% and 50%, respectively. The activities of these enzymes on CMC-Na were increased by 128 to 192% when 10 mM MnCl2 was added. Filter paper, microcrystalline cellulose (MCC), steam-pretreated rice straw, rice straw, and wheat straw were efficiently degraded by these fused enzymes. Specific activities of the fusion enzymes on MCC reached 34.4 to 76.4 U/μmol. The results indicated that bifunctional cellulases fused with CBMs were functional on cellulosic biomass, and CBMs contributed to further deconstruction of MCC and other natural substrates.

A comparison among ten market pulps at a laboratory scale using uncreped tissue handsheets was performed to study the performance of wood and non-wood pulps for tissue manufacturing, evaluate what fiber features are desired for a specific tissue property, and determine how non-wood pulps can be used to replace or complement wood pulps in tissue products. A characterization of the fiber morphology and handsheet properties (softness, water absorbency, and strength) was performed at different mechanical refining levels. The results showed that the fiber morphology had a major impact on tissue properties. Market pulps with a combination of long fibers, high coarseness, and low fines content can provide superior bulk and water absorbency. Short fibers with thin cell walls and low fines content can impart superior softness. Bleached bamboo soda pulp can replace hardwood and softwood pulps to provide an excellent combination of water absorbency and strength. Bleached bamboo soda pulp can also replace Northern bleached softwood kraft (NBSK) pulp to impart strength without sacrificing softness. Bleached and semi-bleached wheat straw soda pulps presented a similar combination of softness and strength as Southern bleached hardwood kraft (SBHK) pulp. The wheat straw pulps can be used to replace deinked pulp (DIP) pulp to impart intermediate levels of water absorbency and strength.

Compact tension specimens were used to determine the mode I (opening crack) fracture toughness of bamboo scrimber, a bio-based product for engineering applications. The influence of thickness and grain mode were investigated, and the extended finite element method (XFEM) was used to simulate the fracture behavior of bamboo scrimber. The results showed that all of the specimens failed in a brittle way. There were no significant differences in fracture toughness among specimens with different thicknesses; however, the grain mode did have a significant effect. The average fracture toughness KIC for T-L and R-L grain modes of bamboo scrimber were 54.32 MPa·mm1/2 and 47.91 MPa·mm1/2, respectively, where the letter “L” represents the longitudinal direction, “R” represents the stack direction, and “T” represents the flattened tangential direction. Based on the results, compact tension specimens with a thickness of 10 mm are recommended to measure the mode I fracture toughness of bamboo scrimber. Furthermore, XFEM was confirmed as a useful tool to investigate the fracture behavior of bamboo scrimber.

Anaerobic co-digestion (AD) of Cynodon dactylon grass and cow dung was conducted with four different composition levels. To increase lignocellulose digestibility and methane yield, grass was pretreated with NaOH and thermally-modified bentonite was used to inhibit the ammonia production. The highest cumulative methane yield obtained from treatments C (0.40:0.60), D (0.60:0.40), and B (0.20:0.80) was 427 mL/ g.VS, 333 mL/g.VS, and 303 mL/g.VS, respectively, over a digestion period of 40 days at a mesophilic temperature. Treatment C showed an 89.7% increase in the methane yield with respect to the control, followed by treatment D, which recorded a 48% increase, and treatment B at a 34.6% increase. A modified Gompertz model was used to explain the methane generation scenario. The process stability parameters of the anaerobic co-digestion system, such as pH, chemical oxygen demand (COD), electrical conductivity (EC), total solids, total and free ammonia contents, and volatile solids removal were explained in depth in this study.

The possibility of enhancing both mechanical and breakdown properties of oil-immersed transformer insulating paper were considered by introduction of cellulose nanocrystals (CNCs). Two kinds of CNCs were taken into account: the TEMPO-oxidized CNCs (T-CNC) and the sulfuric acid hydrolyzed CNCs (S-CNC). Insulating paper containing no CNCs was also prepared as a reference. Obtained samples were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The effects of different amounts of CNC on tensile strength, AC breakdown strength, oil absorption rate, and conductivity of insulating paper extract were studied. The CNC improved the mechanical and electrical performances of insulating paper, and the effect of T-CNC was a little better than that of S-CNC. When the T-CNC dosage was 0.9%, the tensile strength, AC breakdown strength in oil, and oil absorption rate of the insulating paper were 70.22 N • m/g, 59.8 kV/mm, and 53.1%, respectively, which was improved by 21.7%, 24.6%, and 39.4%, respectively, compared with the reference insulating paper. The beating degree of pulp also affected the mechanical and electrical properties of insulating paper containing CNC. Based on overall performance, it was concluded that CNCs are promising nano-additives for oil-immersed transformer insulating paper, especially for T-CNC.