Volume 11 Issue 1

The influences of stock consistency on the kappa number, residual alkali of pulp, flow direction of lignin, chemical oxygen demand, oxidation with dichromate (CODCr), and five-day biochemical oxygen demand (BOD5) in effluents were investigated in a washing process. Compared with 15% stock consistency, 35% stock consistency could lead to a decrease of at least 25% in the consumption of washing water while cutting 75.27% and 46.29% of CODCr and BOD5 in washing effluents, respectively. Moreover, the residual lignin in effluents were reduced greatly from 39.35 g·t^-1 to 12.76 g·t^-1, which will be beneficial to treatment of washing and bleaching effluent. All the results showed that a higher stock consistency in the washing process could decrease the consumption of washing water, the generation of pollution, and the toxicity in bleaching effluent.

The fibers of oil palm empty fruit bunch (OPEFB) stalks were investigated to determine the changes in their basic properties after oven-heat treatment. The oven-heat treatment was conducted at 100 °C or 190 °C for 15 min. There were slightly noticeable morphological, chemical, and thermal alterations in oven-heat treated OPEFB stalk fibers for short duration. Scanning electron microscopy (SEM) revealed that the treated fibers had smooth surfaces and irregular heavy deposition of cementing agents. The highest cellulose content (41.68%) was present in OPEFB stalk fibers treated at 100 °C for 15 min, whereas the highest crystallinity index (48.74%) occurred in fibers treated at 190 °C for 15 min. The fibers comprised cellulose, lignin, and hemicellulose with a high percentage of C, O, K, and other elements. Based on differential scanning calorimetry (DSC) analysis, oven-heat treated and untreated OPEFB stalk fibers had similar thermal stability characteristics.

This work deals with the influence of specific pressure during the press process on the radial and tangential penetration of urea-formaldehyde (UF) adhesive into poplar, as well as on the shear strength of lap joints prepared at these different pressures. An epi-fluorescence microscope was used for measuring the adhesive penetration when investigating microtome slides (20-µm thick) cut from the joint samples. The average penetration depth (dap) and the size of the interphase region (I) increased with the increase of pressure from 0.5 to 1.0 N/mm2. Further increase in the pressure to 1.5 N/mm² did not produce a significant change in dap or I. On the contrary, the area of filled lumens and rays (A) showed a steady decrease as the specific pressure increased. Such behavior influenced the filled interphase region (If), which also decreased with increased pressure. Tangential samples (radial penetration) obtained higher values of lap shear strength and showed less dependence on the specific pressure than the radial samples (tangential penetration). Higher shear strength based on radial penetration corresponded to the thicker interphase region of these samples. The highest shear strength for both directions of penetration was obtained for the specific pressure of 1.0 N/mm².

Tannin-formaldehyde resins (TFR) were prepared by copolycondensation of tannins (larch tannin or valonia tannin) and formaldehyde. The performances of TFR and the free formaldehyde residue in the system during the course of reaction were tested. Chemical and structural changes of TFR during the reaction process were detected by Fourier transform infrared spectroscopy (FTIR) and 13C nuclear magnetic resonance spectroscopy (13C NMR). The results indicated that larch tannin-formaldehyde (LTF) resins demonstrated higher viscosity, higher solids content, shorter gel time, and lower free formaldehyde content than valonia tannin-formaldehyde (VTF) resins. The FTIR and 13C NMR tests demonstrated that larch tannin had higher reactivity than valonia tannin with formaldehyde, which was confirmed by the results of the free formaldehyde content measurement and the characteristics of TFR.

The properties of poly(lactic acid) (PLA) bio-composite films reinforced with oil palm empty fruit bunch (OPEFB) fiber and nanosilica were studied in this work. The composite films were prepared via the solvent casting method. The composites were characterized via Fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy, field-emission scanning electron microscopy (FESEM), tensile testing, and X-ray diffraction (XRD). Ultraviolet visible spectroscopy results revealed that the PLA-based composites and neat PLA had similar light transmittances of approximately 89%. The FTIR and FESEM results showed that OPEFB fibers and nanosilica were embedded into the PLA matrix. The tensile strength of the composites with addition of nanosilica increased with an increasing fiber load content. The XRD analysis showed that the addition of organic or inorganic silica reduced the crystallinity of the composites. The water vapor permeability test results indicated that the inorganic silica decreased the diffusion rate of water molecules through the polymer film. The OPEFB-reinforced PLA blend with additional organic silica exhibited a higher thermal stability than the composites reinforced with inorganic silica.

The state of Wisconsin has existing pulp mill infrastructure capable of converting wood into biofuel and value-added products such as lumber, pulp, and paper. Each day, pulp and paper mills produce a waste material that is commonly referred to as sludge. Sludge is typically sent to a landfill or concentrated for burning to produce steam. The primary material present in pulp and paper mill sludge is fiber, which is mostly cellulose. This study showed how to convert pulp mill waste to fermentable sugars using commercially available enzymes. Preliminary economic analysis has shown that sludge can be converted into a fermentable sugar with chemicals costing less than $0.10 per pound of sugar produced.

Sugarcane bagasse (SCB) was modified by steam explosion pretreatment at 190 °C for 10 min and 210 °C for 5 min using green liquor (GL) combined with hydrogen peroxide (GL-H2O2) and ethanol (GL-Ethanol) for simultaneous saccharification and fermentation (SSF)-based ethanol production. The results showed that 85.02% and 100% of hemicelluloses were solubilized by steam explosion pretreatment at 190 °C for 10 min and 210 °C for 5 min, respectively. Moreover, 20.08% and 73.77% of the lignin was removed through GL-H2O2 and GL-Ethanol pretreatments, respectively. The steam explosion pretreatments greatly improved the specific surface area of the SCB and led to the highest ethanol yield of 92.20% at 190 °C for 10 min and 93.19% of 210 °C for 5 min, respectively. In addition, the ethanol yield reached 72.58% for the GL-Ethanol pretreatment, and about 70% of active lignin could be recovered from the pretreatment liquid. When the GL-H2O2 pretreatment was used, the maximum ethanol yield of 20.92% was achieved.

A new synergetic flame retardant system (SFRS) using ammonium polyphosphate/melamine cyanurate (APP/MCA) core-shell particle was synthesized and applied to papermaking. Cationic polyacrylamide (CPAM) was added to improve the adsorption of SFRS in pulp. Higher amounts of SFRS led to higher adsorption by pulp. Handsheets were produced with different amounts of SFRS. Thermal gravimetric analysis (TGA) and limiting oxygen index (LOI) were employed to test fire retardation in these handsheets. TGA and LOI results showed that this new core-shell SFRS is an effective flame retardant that improves the thermal stability of handsheets.

A lignin-epoxy resin composite was prepared by blending lignin/wood flour with an epoxy resin and polyamine. The effects of the wood flour on the mechanical, thermal creep, and creep recovery properties, as well as the microstructure of the composite, were studied. Among the mechanical properties, the initial modulus increased with increasing content of wood flour. The glass transition temperature (Tg) decreased, and the thermal stability first decreased and then increased, as the wood flour content increased. As the wood flour’s particle size was decreased, the initial modulus and other mechanical properties first increased and then decreased slightly. The Tg increased, and the thermal stability first decreased and then increased. The creep resistances of the composite were improved after the addition of the wood flour, and the 40 to 60 mesh wood flour exhibited better improvement than 60 to 120 mesh. The scanning electron microscopy (SEM) analysis revealed good interfacial bonding between the lignin, epoxy resin, and wood flour. Fiber breakage and fiber pullout were the main failure modes observed in this study.

Several physical and mechanical properties of particle board were investigated using estimation modeling. Particleboards (0.65 g/cm3) were produced for five experimental groups, in which lavender plant waste, red pine chips, and urea formaldehyde (UF) resin were mixed in different proportions. After immersing the particleboards in water for 24 h, several properties including thickness swelling (TS), modulus of rupture (MOR), modulus of elasticity (MOE), and internal bond strength (IBS) were determined. The statistical relevance of the experimental results was evaluated using multi-variance analysis (ANOVA), and the homogeneity between experimental groups was evaluated using Duncan tests. With the use of variable inputs and experimental results, estimation models using polynomial curve fitting(CF), adaptive neural networks (ANN), and an adaptive neuro-fuzzy inference system (ANFIS) were generated. The results obtained from the estimation models and experiments were then compared via root-mean-square error (RMSE) and R2 values. The ANFIS estimation model was the best alternative to the costly, long-term experimental methods, as it produced more economical and reliable results in a shorter period of time.