Volume 9 Issue 3

The purpose of this study was to investigate the mechanical and thermal properties of high-density polyethylene (HDPE) composites reinforced by bamboo pulp fibers (BPF). Using a twin-screw extruder, polymer composites were fabricated using BPF and bamboo flour (BF) as the reinforcement and HDPE as the matrix. Tensile and flexural tests of the HDPE composites were performed to determine the mechanical properties under different conditions. The thermal properties of HDPE composites were characterized by thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The results showed that BPF improved the mechanical and thermal properties of the polymer composites more than did BF. The tensile and flexural strength of composites with 30 wt% BPF were increased by 61.46% and 22.94%, respectively, while the tensile and flexural modulus were increased by 84.52% and 27.30%, respectively. Compared to composites with 50 wt% BF, the T5% of composites with 50 wt% BPF increased by 20.18 °C. As the BPF content increased, the storage modulus (E’) and loss modulus (E”) initially increased, followed by a decrease. Compared to the BF/HDPE composites, BPF/HDPE composites reinforced at 30 wt% had a higher storage modulus (E’) and loss modulus (E”) and lower damping parameter (tanδ).

Ts, and viscose fibers by wet-laid nonwoven technology. The best process conditions included a basis weight of 30 g/m2, a bamboo paper sludge content of 10 wt%, and a polyvinyl alcohol concentration of 4 wt%. The burst strength, tearing resistance, tensile properties, resistance to water, and degradation rate were 220.65 kPa, 60.00 N, 46.10 N, 153 Pa, and 56.18%, respectively, under the best process conditions. The biodegradable paper sheeting can satisfy the demand for replacement of agricultural plastic sheeting used for such purposes as moisture retention of soil and promotion of plant growth.

The improving effect of an increase in the thermal conductivity caused by nano-wollastonite (NW) on the physical and mechanical properties of medium-density fiberboard (MDF) was studied. Nanowollastonite was applied at 2, 4, 6, and 8 g/kg, based on the dry weight of wood-chips, and compared with control specimens. The size range of wollastonite nanofibers was 30 to 110 nm. The results show that NW significantly (p < 0.05) increased thermal conductivity. The increased thermal conductivity resulted in a better curing of the resin; consequently, mechanical properties were improved significantly. Furthermore, the formation of bonds between wood fibers and wollastonite contributed to fortifying the MDF. It was concluded that a NW content of 2 g/kg did not significantly improve the overall properties and therefore cannot be recommended to industry. Because the properties of NW-6 and NW-8 were significantly similar, a NW-content of 6 g/kg can be recommended to industry to significantly (p < 0.05) improve the properties of MDF panels.

Treatment with water-soluble low-molecular weight phenol-formaldehyde resin is an effective method to improve wood properties. In this paper, plantation wood of Chinese fir was modified with low-molecular weight phenol-formaldehyde resin. The absorbance by tracheid cell walls of phenol-formaldehyde resin in treated and untreated reference samples were measured with an ultraviolet micro-spectrophotometer. The UV absorbance values of earlywood tracheids and middle lamella in treated wood were significantly increased, with an average increase of 49% and 23%, respectively. Moreover, after treatment with low-molecular weight phenol-formaldehyde resin, the UV absorbance of the earlywood tracheid cell walls of Chinese fir increased to more than 47%, regardless of whether or not the cell lumens were filled with resin. After treatment with low-molecular weight phenol-formaldehyde resin, the UV absorbance of earlywood tracheid cell walls at different locations did not vary greatly. This study provides direct support for the improvement of the physical and mechanical properties of resin-modified Chinese fir in terms of penetration of the resin into the cell walls.

Alkali pretreatment is one of the leading pretreatment technologies for biofuel applications. The histochemical and structural characteristics of poplar cell walls were investigated before and after sodium hydroxide pretreatment (121 oC, 2%) to understand the alterations in biomass cellular structure, which were correlated with saccharification yield. Results showed that alkali pretreatment preferentially removed lignin from the S2 of fibers, which was similar to the behaviors of coniferyl alcohol and aldehyde (lignin-CAA), exhibiting a positive correlation between removal of the two structures. Additionally, the cellulose microfibril angle was enlarged as the residence time increased during pretreatment. Scanning electron microscopy (SEM) analysis further suggested that pretreatment caused ultrastructure changes in cell walls with cracks formation on cell wall surface, especially in the areas adjacent to the cell corner middle lamellar (CCML). Accordingly, the cellulose digestibility of residues increased from 32.1% for the raw material to 53.7% for the treated samples obtained in 72 h. It can be concluded that the changes in topochemistry and ultrastructure of poplar cell walls resulting from alkali pretreatment mediated the efficiency of enzymatic hydrolysis of residues.

Wood-plastic composites (WPCs) represent a growing class of durable, low-maintenance construction materials whose use can decrease dependence on petroleum. High-density polyethylene (HDPE), chitosan (CS), wood flour (WF), boric acid (BA), and borax (BX), as well as maleic anhydride grafted polyethylene (MAPE) and polyethylene wax (PE wax), were used to develop a durable wood-plastic composite (WPC) using the extrusion method. The effects of boron compounds (3%, 6%, 9%, or 12% by weight BA/BX) on the mechanical and fire properties of the WPCs were investigated. Mechanical testing indicated that as the percentage weight of boron compounds increased, the flexural modulus, flexural strength, and tensile strength significantly decreased. Cone calorimeter tests were used to characterize the fire performance of the WPCs, and these results suggested that adding BA/BX compounds to WPCs modestly improved the fire performance. As the percentage weight of BA/BX increased from 3% to 9%, the time to ignition (TTI), heat release rate (HRR), total heat release rate (HRR-Total), smoke production rate (SPR), and specific extinction area (SEA) of the WPCs were all reduced.

A series of sulfated zirconia-titanium dioxide (SO₄^2-/ZrO₂-TiO₂) catalysts with different Zr-Ti molar ratios were prepared by a precipitation and impregnation method and characterized by ammonia adsorption/ temperature programmed desorption (NH₃-TPD), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques. The catalysts were used in the catalytic conversion of a sugar mixture (glucose and xylose) to 5-hydroxymethylfurfural and furfural in a water/n-butanol reaction system. An optimized yield of 26.0 mol% for 5-hydroxymethylfurfural and 47.5 mol% for furfural was obtained within 2 h at 170 °C over the SO₄^2-/ZrO₂-TiO₂ catalyst with a Zr-Al molar ratio of 7:3. Catalysts with higher acidity and moderate basicity were more favorable for the formation of the target product.

The current Chinese Standard (GB5889-86 1986) for wet chemistry determination assumes that there is no temperature degradation of sugars during hot water extraction. There is therefore a need to quantify this level of error and propose possible solutions for future revisions. This research was performed to investigate the thermal resistance of polysaccharides in common fibrous materials. A two-factor, two-level experimental design was employed, in which pre-oven drying and water bath temperature were controlled and changes in extractive content were measured. The thermodynamic equations for polysaccharide thermal degradation in ramie and wood were calculated. High-performance liquid chromatography (HPLC) was employed to identify monosaccharide changes during the process. This study found that polysaccharides in fibrous materials have considerable thermal degradation during oven drying at 100 °C and hot water treatment. Lower temperature combinations are recommended during hot water extractive testing when sugar analysis is to be subsequently performed.

Submerged culture conditions for laccase production by Pleurotus ostreatus were optimized by response surface methodology (RSM). A total of six factors, carbon (glucose), nitrogen sources (urea and peptone), 2,5-xylidine (inducer), wheat bran (lignocellulosic material), and medium pH, were optimized. A total of 50 experiments were conducted, and the obtained data were modeled using a second-order polynomial. The optimized conditions show significant improvement in laccase expression, by approximately 3.5-fold (12,124 U/L).

Wetting of coated papers by isopropyl alcohol (IPA)-based fountain solutions or surfactant solutions was studied in this paper. Additionally, the effect of paper surface properties on wetting was analyzed. To that end, six fountain solutions were prepared. Three solutions had increasing amounts of IPA, and three were made from surfactant-based dampening agents. Eight commercial coated papers were selected and characterized in terms of roughness and surface free energy. Paper resistance to wetting by fountain solutions was evaluated by measuring the static and dynamic contact angles. Static contact angles between the paper surface and the IPA-based fountain solutions decreased as the alcohol concentration increased, whereas the wettability with surfactant-based fountain solutions was highly dependent on their surface tensions. Paper surface free energy strongly affects the static contact angle and only moderately affects the dynamic contact angle.