Volume 12 Issue 4

Wood veneer/biopolyethylene (bio-PE) biocomposite materials were produced by using poly(N-vinylformamide-co-vinylamine) (PVFA-co-PVAm) copolymers as a phase-mediating reagent. In a preliminary step, PVFA-co-PVAm was adsorbed onto the wood veneer component from aqueous solution. In its adsorbed form, it served as an adhesion promoter and improved the compatibility between both the highly polar wood veneer and weakly polar bio-PE surface. Structural parameters and their effect on the adsorption process, such as the degree of hydrolysis (DH) of poly(N-vinylformamide) (PVFA) (30, 50, and > 90%), the molecular weight of PVFA-co-PVAm (Mw 10,000, 45,000, or 340,000 g/mol), and the pH value (4, 7, and 11) influenced the resulting wetting behavior of the PVFA-co-PVAm-modified wood veneer surface. Thus, the hydrophobizing effect of the PVFA-co-PVAm was clearly detectable because the contact angle with water was considerably increased up to 116° by adsorption of PVFA-co-PVAm 9095 at pH 11. The adsorbed amount of PVFA-co-PVAm was determined by energy-dispersive X-ray (EDX) spectroscopy and X-ray photoelectron spectroscopy (XPS). The PVFA-co-PVAm-coated wood veneers were consolidated with bio-PE in a hot press process. The modified composite materials showed remarkably improved Young’s moduli (552 MPa) and tensile strengths (4.5 MPa) compared to former composite materials produced without PVFA-co-PVAm modification.

Yaupon holly is one of the most widespread woody underbrush species in the southeastern United States, and it can undermine forest health and safety due to its biofuel-like nature during catastrophic wildfires. Yaupon holly was subjected to microwave liquefaction to produce biobased polyurethane (PU) foam insulation. Liquefaction parameters were optimized and summarized as follows: 1) particle size was controlled in the range of 16- to 40- mesh; 2) both the ratios of glycerol to ethylene glycol and liquid to solid were set at 3:1; 3) the reaction process was conducted at 160 °C for 10 min and catalyzed by 1.5% sulfuric acid. The optimal liquefaction conversion yield was 94.9%. The Fourier transform infrared spectra (FTIR) indicated the successful liquefaction and dissolution of wood essential components, i.e. hemicellulose, cellulose, and lignin. The optimal liquefaction product with solid residue was used directly to produce biofoams. With an increased isocyanate index, the thermal insulation properties, mechanical properties, and thermal stability of biofoams increased. Therefore, a promising biobased PU foam was obtained at an isocyanate index of 150. The density, thermal conductivity, Young’s modulus, and compressive stress of the promising biofoam were 18.5 kg·m-3, 0.033 W·m-1·K-1, 176.7 kPa, and 15.4 kPa, respectively.

Two samples of acid-hydrolyzed nanocellulose and two samples of TEMPO-oxidized nanocellulose were separately prepared from cotton liner pulp and microcrystalline cellulose, and dispersed in water. Sodium alginate that was extracted from brown seaweed was dissolved in the nanocellulose suspensions and wet spun in a calcium chloride bath to form four kinds of alginate/nanocellulose composite fibers. The structures and properties of the obtained nanocellulose and composite fibers were investigated and compared. The results showed that all of the nanocellulose samples exhibited a needle shape with slightly different sizes. The incorporation of nanocellulose increased the opacity of the spinning dopes but improved the mechanical properties of the alginate fibers. The optimum addition amount for all of the nanocelluloses was 5% (based on the weight of sodium alginate). The TEMPO-oxidized nanocellulose produced from cotton liner pulp had the greatest influence on the strength of the fibers. All the composite fibers had an irregular cross-section with dense and uniform structure, which indicated the good compatibility between nanocellulose and alginate. In addition, the introduction of nanocellulose slightly improved the thermal stability of the alginate fibers.

The increased functionality of cellulose fiber based paper products is of high interest, as researchers are investigating methods to replace petroleum-based products with modified paper products. In this study, fully bleached wood pulps were treated with atmospheric pressure plasma, made into paper handsheets, and then tested for surface and other physical properties. Paper handsheets after formation were also treated with plasma to induce surface modifications. The plasma was generated using helium with fractions of either O2, CF4, or C3F6 to determine the effect of the nature of the gas. Drying methods had a greater effect on strength properties and density than plasma treatment. Plasma treatments on previously made paper increased the surface roughness, but plasma treatments on pulps prior to papermaking did not cause any roughness changes in the resulting paper. X-ray photoemission spectroscopy (XPS) revealed small increases in the oxygen to carbon ratios of oxygen enhanced plasmas for both pulp and paper treated samples. The plasma treatment showed evidence of surface fluorine in paper treated with CF4 containing plasma, but not in pulps treated with CF4 containing plasma and then made into paper.

Separation and structural characterization of lignin are essential for value-added utilization of hemicelluloses and lignin in the prehydrolysis liquor (PHL) of a kraft-based Whangee (a genus of bamboo) dissolving pulp production. In this work, lignin in the PHL was separated by acidification treatment (AT) and rotary vacuum evaporation treatment (RVET), and the separated crude lignin was then compared and characterized. The crude lignin separated by RVET could be justified as p-hydroxyphenyl (H) -syringyl (S) -guaiacyl (G) lignin, and a conjugated carbonyl was also found in it. The crude lignin separated by AT was mainly composed of S lignin that had β-1, β-5, β-O-4, and β-β bonds. Thermogravimetric analysis (TGA) showed that the maximum thermal decomposition temperatures and the final carbon residues of crude lignin separated by RVET and AT were 520 °C, 5.26%, and 470 °C, 27.92%, respectively. Moreover, of the five kinds of sugar (arabinose, galactose, glucose, xylose and mannose) in the PHL, only galactose and glucose were decreased after AT, while all five kinds were decreased after RVET.

Bamboo and wood fibers are important raw materials for pulp and papermaking, as well as fiber-reinforced composites. The mechanical properties of single fibers and the cell walls of moso bamboo (Phyllostachys heterocycla), Masson pine (Pinus massoniana), and Chinese fir (Cunninghamia lanceolata) were tested via single fiber tensile test and nanoindentation; their fracture characteristics were also compared. The single fibers and cell walls of moso bamboo had superior mechanical properties compared with those of Masson pine and Chinese fir. The bamboo fibers exhibited high strength, high elasticity, and superior ductility. The results indicated that the differences between the mechanical properties of the fiber cells and cell walls of moso bamboo and those of wood were largely dependent upon cell shape and structure.

The pyrolysis potential of corn stover digestate (CSD) was compared with corn stover (CS). The effects of anaerobic digestion (AD) on pyrolysis were investigated at different rates by a thermogravimetric analyzer coupled with Fourier transform infrared spectrometry (TG-FTIR). The distributed activation energy model (DAEM) was used to show the differences in the kinetics. The results indicated that the AD process improved the thermal stability with lower mean reactivity (RM), higher solid residue (S850), and decreased release of observed gaseous productions, except for CH4. The release of CH4 from CSD was higher than that of CS, especially in the temperature range of 430 °C to 520 °C. The activation energies (E) of CS and CSD were 184 kJ/mol to 293 kJ/mol (conversions were 0.1 to 0.8) and 99 kJ/mol to 331 kJ/mol (conversions were 0.1 to 0.9), respectively. The activation energies decreased after AD at the same conversion level. The calculated TG data of CS and CSD from the kinetic parameters were in good agreement with the experimental curves.

This study investigated the blending of unbleached wheat straw high yield MEA (monoethanolamine) pulp with recycled pulp to improve the strength properties of recycled pulp. First, the cooking temperature in MEA high yield pulping was stepwise reduced from 160 °C to 120 °C to enhance pulp yield as much as possible. The optimum temperature for the intended application was 130 °C. In the second series of cooking performed at this temperature, the MEA charge was gradually reduced. However, with the reduction of MEA charge, the Kappa number rapidly increased. The solvent recycling was considered in a third series by reusing black liquor two times. The Kappa number increase, due to partial reuse of black liquor, was low, and the pulp strength remained at a high level. A MEA straw pulp, prepared without black liquor reuse, was refined with low energy input to various beating degrees to evaluate the refining behavior and strength development. The MEA straw pulp samples with different beating degrees were blended with recycled pulp. The ratio of blending varied between 5% and 20%. The results revealed that MEA straw pulp was well-suited as a reinforcement pulp. All strength properties of the recycled pulp, except tear strength, were improved.

A combination of extracellular enzymes secreted by Irpex lacteus KB-1.1 and Lentinus tigrinus LP-7 showed promising results in the reduction of kappa number of Acacia oxygen-delignified kraft pulp (A-OKP) in previous studies. However, the observed Kappa number reduction was low, and the bleaching process required further optimization. In the current study, the A-OKP was treated with a combination of extracellular enzymes of I. lacteus and L. tigrinus, with a subsequent alkaline peroxide extraction, which significantly improved the Kappa number reduction. The maximum achieved Kappa number reduction was 26%. The effects of static incubation and sterilization of the extracellular enzymes on biobleaching process were evaluated. Compared with a static biobleaching, biobleaching with shaking shortened the required incubation time required from 3 to 1 d. The utility of extracellular enzymes was tested with and without sterilization; no significant differences in Kappa number reduction, brightness, and physical properties of the pulp were observed. The physical properties of all pulp samples were improved following the enzymatic treatment. Furthermore, a low-cost medium containing wood powder supplemented with rice bran and palm sugar (WRBP) was used for the production of enzymes for biobleaching of A-OKP.

To investigate the effects of acidity on aromatic yield and selectivity during the catalytic pyrolysis of biomass, the silica to alumina ratio (SAR), as well as the amount and addition method of HZSM-5 catalyst were varied. The results showed that with an increase in the SAR, the pore volume was reduced, the average pore diameter of the HZSM-5 catalyst increased, and the total acidity and catalytic activity decreased. Meanwhile, the increase in acidity led to an increased non-condensable gases yield, which was associated with a decrease in the bio-oil yield. The calorific value and moisture content increased, and the ability of deoxygenation was enhanced. The single ring aromatic hydrocarbons (BTXE) content increased, and the polycyclic aromatic hydrocarbons (2-ring, 3-ring) content decreased noticeably. The selectivity of BTXE decreased substantially from 69 wt.% to 6.85 wt.%, while the selectivity of naphthalene and its derivatives increased remarkably, as the SAR increased. Additionally, the acidity increased the selectivity of unsubstituted aromatic compounds, but decreased the selectivity of substituted aromatic compounds. Moreover, ex situ catalytic pyrolysis more effectively enhanced the aromatic hydrocarbon yield and selectivity (69 wt.%) compared with in situ catalytic pyrolysis (27.51 wt.%), and in situ catalytic pyrolysis generated more polyaromatics and solid residue.