Volume 16 Issue 2

Pseudo-lignin derived from the condensation of carbohydrate degradation products can retard the bioconversion of lignocellulose. In this work, liquid hot water (150 to 190 °C) and 1% H2SO4 pretreatments (130 to 190 °C) were used on sugarcane bagasse holocellulose for 3 h to generate pseudo-lignin. The effects of pseudo-lignin generation on structural characteristics and bioconversion of substrates were evaluated. The results showed that the formation of pseudo-lignin increased the hydrophobicity of the substrates. After LHW pretreatments and acid pretreatments at low temperatures (<150 °C), most of the xylans were removed, yielding 2.1 to 5.4% pseudo-lignin. Increasing acid pretreatment temperature to 170 and 190 °C yielded 34.3% and 93.6% pseudo-lignin, respectively. After pretreatment, the accessibilities and bioconversions of substrates were enhanced by degradation of xylans, increasing glucose conversions and bioethanol productions of substrates from 53.2 to 85.3%, and 9.9 to 13.1 g/L, respectively. However, large amounts of pseudo-lignin were generated during acid pretreatments at 170 °C, reducing glucose conversion and bioethanol yield to 45.6% and 6.3 g/L, respectively.

Low-field nuclear magnetic resonance (NMR) technology was used to perform the experiments of transverse relaxation time (T2), pore size distribution, and water absorption rate for wood-plastic composites (WPC) with different contents of added slag powder, exploring the water movement and the dynamic changes of pore size during the moisture absorption process of the material under immersion condition. The experimental results were as follows: (1) According to the T2 of H proton and its inversion pattern, the measured porosity had a relatively small difference from that of the weighing method. (2) The pore size distribution graph showed the following: (i) when the immersion time of composite materials was different, the changing law of volume of pores with different radius was different.; (ii) when the material’s immersion time was greater than 216 h, the pore radius and its distribution characteristics showed large differences; (iii) slag powder changed the pore structure of the WPC but did not change the water absorption characteristics of the wheat straw. (3) The changes of water absorption and expansion rate showed that the slag powder changed the time for the materials’ pores to absorb water until saturation and reduced the water absorption and expansion rate. The measurement results were consistent with changing trend in the pore size obtained by low-field NMR relaxometry.

A desire to develop biorenewable materials has led to lactide–caprolactone copolymers being used in adhesive, medical, and pharmaceutical products. Use of this alternative material may diminish human impact on the environment and create products that are biocompatible. One advantage of these materials compared with other typical petroleum-based polymers is that they are easily degraded by microorganisms. In this study, the biodegradation of representative lactide–caprolactone macromonomers and an acrylic pressure sensitive adhesive incorporating these macromonomers was followed by a respirometric method using a consortium of microorganisms found in a typical wastewater treatment facility. The weight loss data of lactide–caprolactone macromonomers showed that the lowest molecular weight macromonomers with a high percentage of lactide had the greatest weight loss, which could have been caused by the greater number of ester linkages. Proton nuclear magnetic resonance data showed that for lower molecular weight copolymers, there was a preferential loss of caprolactone. Promisingly, testing of the full acrylic adhesives showed that they were easily degraded and thus provided a route to more environmentally friendly adhesive products.

Because of its hardness, wear-resistance, strength, and bending capabilities, beech wood is a widely-used hardwood in Europe. It is mainly used for furniture, floors, construction, veneer boards, and laminated wood. For such uses, the mechanical properties are very important, especially in cases of impact loads. The aim of this work is to analyse the mechanical properties of beech wood samples exposed to compressive force in the longitudinal direction based on different loading rates (in the range from 10 mm/min to 500 mm/min). Stress–strain diagrams were made with the experimental data, and mathematical functions were fit to them. Using the fit functions, the following properties of beech wood samples were determined: the stress and strain at the elastic limit; the maximum stress and associated strain; the modulus of elasticity; the tangent modulus; the specific energy of elastic strain; and the specific energy of plastic strain. The results showed that by increasing the loading rates, the elastic properties of beech wood increase, while the analysed plastic properties do not show a clear tendency of changes with increase of the loading rates.

Utilization of lignin phenol glyoxal (LPG) resins was studied as a potential alternative for phenol formaldehyde (PF) resins. Lignin was extracted by alkaline pulping processes (kraft and soda) from date palm fronds (DPF) and was used as an alternative for phenol in LPG resins. The isolated lignin samples were characterized using complementary analyses that included Fourier transform infrared (FTIR) spectroscopy, 13C nuclear magnetic resonance (NMR) spectroscopy, thermal stability, thermogravi-metric analysis (TGA), and differential scanning calorimetry (DSC). Kraft lignin phenol glyoxal (KLPG) and soda lignin phenol glyoxal (SLPG) resins also were characterized in terms of solid content, viscosity, and gel time. Finally, physico-mechanical tests were performed on plywood panels that were treated with different molar ratios of LPG resins. The results revealed that 50% (w/w) KLPG resin resulted in higher tensile strength (65.3 MPa) than PF resin (58.57 MPa), which was potentially attributed to the higher amount of phenolic groups compared to soda lignin. Therefore, the substitution of DPF lignin in LPG resins enhanced the adhesive in terms of its chemical and mechanical properties, enabling it to produce a more environmentally friendly wood adhesive.

In order to study the aesthetic preferences of individuals in terms of wood color, the authors explored the preference for red sandalwood and wenge wood of different hues and lightness values through a combination of an eye movement technique and subjective evaluation. The experimental results showed that: (1) sex factors had a significant effect on the eye movement indexes in a modern aesthetic preference experiment; (2) the preferences of the subjects varied slightly with different wood types but in a lower range; and (3) the effective eye movement indexes in this study were fixation duration, number of fixations, and number of last-sampling positions; in addition, there were differences in the effective eye movement indicators in different experiments. The subjects preferred a low lightness value or color of the chair.

The compaction behavior of cotton stalk particle mats, temperature profile inside the particle mats, and influence of surface particle size were studied relative to the properties of three-layered cotton stalk particleboards. Modulus of rupture (MOR), modulus of elasticity (MOE), internal bond, and thickness swelling were used as a measure for mechanical and physical performance. Two types of cotton stalk particleboard were manufactured. Results indicated that compression stiffness of the particle mat increased with increasing particle size; however, it decreased with increasing mat moisture content and temperature. At mat moisture contents of 12% and 18%, the plateau temperature at the centerline was not significantly different between boards having coarse and fine particles. However, the plateau time of boards with coarse particles was significantly lower than that of boards with fine particles. Additionally, thickness swelling of boards with a surface particle size of 2 mm was significantly lower than that of boards with surface particle size of 4 mm. Boards with a surface particle size of 2 mm had MOR and MOE values 15% and 10% higher, respectively, than boards with surface particle size of 4 mm. Internal bond decreased 6.5% with decreasing surface particle size from 4 mm to 2 mm.

This study investigated the effects of the pressing temperature on the mechanical and physical properties of binderless bark particleboard made from Gelam bark waste and the improvement of those properties. In addition, the thermal insulation properties of the particleboard were determined. Four different temperatures (140 °C, 160 °C, 180 °C, and 200 °C) were used to make single-layer binderless bark particleboard with a target density of less than or equal to 0.59 g/cm3. Results revealed that the pressing temperature affected the mechanical properties (modulus of rupture, modulus of elasticity, and tensile strength perpendicular to panel surface), which increased as the temperature increased, and the physical properties (thickness swelling and water absorption), which decreased as the temperature increased. Based on the Tukey test, increasing the temperature from 180 to 200 °C did not significantly affect the mechanical or physical properties, except for the tensile strength perpendicular to panel surface. None of the mechanical properties met SNI standard 03-2105-2006 (2006); however, the 12% maximum thickness swelling requirement was met for binderless bark particleboard hot-pressed at 200 °C. Binderless bark particleboard hot-pressed at 200 °C had high water resistance, regardless of its low strength, and a thermal conductivity value of 0.14 W/m∙K.

Characterization of Ceiba aesculifolia (CA) fibers by various techniques is herein reported. The seed pods were collected, and the fibers surrounding the seeds were characterized or treated in an oven at 100 °C prior to characterization by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis coupled with a differential scanning calorimeter (TGA-DSC). The SEM micrographs showed that the natural material is comprised of tubes of external diameter of approximately 27 μm and a mean wall thickness of about 0.62 μm. The results also indicated that the tubes begin to decompose at approximately 220 °C.

Different types of rotor-stator and jet-impingement refining equipment are used depending on the methods of production of fibre semi-finished products and on the initial state of raw materials. This article examines various refining modes for jet-impingement devices and their influence on the physical and mechanical properties of the processed material. Main design parameters that affect the refining process in this type of plant were determined. It was shown that the time required to refine a fibre mass using this plant depends on the jet flow rate (from the nozzle to the barrier), i.e. as the jet flow rate increases, the time required to refine the fibre mass decreases. A dimensionless machine parameter was obtained that characterises the effectiveness of the refining process and the design of jet-impingement refining plants. Using the dimensional method, a functional dependence was observed of breaking length, bursting strength, folding strength, and tearing strength on the machine complex parameter. The numerical value of the machine complex parameter was determined, depending on refining duration.