Research Articles

The characteristics of two novel types of technical lignin, namely Ecohelix (EH) and CleanFlow black lignin (CFBL), isolated from two different pulping process side streams, were analyzed. EH and CFBL were analyzed in terms of general composition, chemical functionalities, molar mass distribution, and thermal stability. For comparison, two relevant types of commercially available lignosulfonate and kraft lignin were used. The results showed that EH contains a large amount of sulfonated lignin, together with carbohydrates and ash. As such, it can be considered a lignin-carbohydrate hybrid molecule. CFBL was found to contain 91.5% Klason lignin and the lowest amount of carbohydrates (0.3%). EH showed the highest content of aliphatic OH groups (5.44 mmol/g) and CFBL a high content of phenols (4.73 mmol/g). EH had a molecular weight of 31.4 kDa and a sufficient thermal stability. CFBL had the lowest molecular weight (M_w = 2.0 kDa) and thermal stability of all kraft lignins analyzed in this study. These properties highlighted that EH is a suitable building block for material development and that CFBL is a promising material for the production of biofuel and biochemicals.

The compressive strength of irradiated hybrid composite materials was investigated via compression testing. The hybrid composites consisted of Kevlar fibre, oil palm empty fruit bunch (EFB) fibre, and epoxy. The hand lay-up method was used to fabricate the samples. The samples were then irradiated with different gamma radiation doses: 25 kGy, 50 kGy, and 150 kGy. Compression tests were performed in accordance with ASTM D695 (2015). Compressive strength in Group 1 increased to 30.4 MPa at 25 kGy. At 50 kGy, the compressive strength further increased to 39.6 MPa. Compressive strength for Group 2 also increased to 58.7 MPa when the radiation increased to 50 kGy. The compressive modulus showed the same trend in compressive strength for both Group 1 and Group 2. It was observed that the exposure of hybrid Kevlar/oil palm EFB/epoxy hybrid composites improved the compressive properties of the materials. Furthermore, a difference in the thickness and layering pattern also influenced the compressive strength with different doses. At 150 kGy, both layering patterns showed a degradation of compressive properties.

As an approach to decrease the fold cracking of coated paper, suspension-polymerized (SP) latexes were developed and tested as a surface sizing additive. Styrene, ethyl acrylate, butyl acrylate, acrylic acid, and itaconic acid were used as monomers for the SP latex, and oxidized starch and polyvinyl alcohol were used as stabilizers. The SP latexes were found to be more stable against the charge neutralization by salt solutions and flocculation by cationic polyacrylamide than conventional styrene-butadiene and styrene-acrylate latexes, and they were highly compatible with the conventional surface sizing solution. The effect of using SP latexes as a surface sizing additive on the mechanical properties of the paper was examined. The SP latexes had greater tensile strength and extensional properties than the emulsion-polymerized latexes, which suggested their potential applicability for reducing the fold cracking of coated paper. A mill trial was performed to test the use of SP latexes as a surface sizing additive, and the results showed that they had a positive effect in reducing the fold cracking of coated paper.

A cyclone gasifier is an effective technology for the gasification of low-density biomass containing a high ash content. The ash removal performance was improved in the gasifier due to being similar to a cyclone dust collector. The cyclone reactor is relatively simple, easy to use, and has low construction costs compared with a traditional fluidized bed gasifier. In this study, the air gasification characteristics of rice straw were investigated in a cyclone gasifier. The results showed that by increasing the equivalence ratio (ER), the gasifier temperature also increased. This, in turn, led to a higher gas quality (higher heating value (HHV) and lower tar content) and enhanced the gasification performance (gas yield, carbon conversion efficiency, cold gas efficiency, and hot gas efficiency). A high ER reduced the amount of the combustible gas component (CO and H₂) and caused the HHV of the producer gas to decrease. The optimum value range of ER was observed to be about 0.29 to 0.34. A smaller feedstock size was more favorable for higher producer gas quality and gasification performance. Biomass moisture content parameters played an important role in the cyclone gasification process. Higher moisture content decreased the gasifier temperature, leading to low gas quality (lower HHV and higher tar content), and resulted in lower gasification performance.

The tradition of using naturally occurring plant fibers is still alive in Africa. In the Uíge province of northern Angola, bast fibers from Triumfetta cordifolia serve as the basis for everyday objects, such as baskets, mats, fishing nets, and traditional clothing. The fibers exhibit a Young’s modulus of 53.4 GPa and average tensile strength of 916.3 MPa, which are comparable to those of commercial kenaf fibers. These values indicate a high potential for use as a reinforcement in biocomposites. Based on this promising mechanical and physical profile of individual fibers, different biocomposites were produced with polylactide (PLA) as a matrix. The obtained composites were analyzed mechanically, physically, and visually. Unidirectionally arranged PLA/33% T. cordifolia composites with continuous fibers showed the highest Young’s modulus (10.79 GPa ± 1.52 GPa) and tensile strength (79.37 MPa ± 14.01 MPa). These composites were comparable to those of PLA/30% hemp composites (10.9 GPa and 82.9 MPa, respectively) and therefore have economic potential.

Tannin and sucrose (TS) can be used in a biomaterial-based wood adhesive that requires a higher hot pressing temperature and longer time than traditional resins. To solve these problems, hydrochloric acid and citric acid were utilized as a catalyst during the curing process to decrease energy costs (forming TSH and TSC adhesives, respectively). Thermal analysis revealed that the addition of hydrochloric acid and citric acid resulted in decreases to the thermal thresholds associated with degradation and curing. The resultant insoluble matter ratio verified that the polymerization reaction happened at a lower temperature than the adhesive without acidic conditions. The FT-IR and solid state 13C NMR spectra showed that the addition of acid compounds acted catalytically and increased the generation of 5-HMF in uncured adhesives. The dimethylene-ether bridges and methylene bridge were formed during the heat treatment. The water resistance of the particleboards manufactured by TSC and TSH adhesives were notably enhanced when the hot-pressing temperature was 180 °C. However, an increased hot pressing temperature did not improve the mechanical properties of the particleboard bonded by TSH, which was due to cellulose and hemicellulose decomposition under strong acidity conditions.

Transgenic Populus trichocarpa wood was compared to the corresponding wild-type material. The static modulus of elasticity in three-point bending was measured and the chemical composition among the specimens were compared, including the glucose, xylose, and lignin contents as well as the S/G ratio. Changes in chemical composition, created by genetic manipulations of the lignin biosynthetic pathway, affect the mechanical properties of young small-diameter transgenic trees. There are indications that a decrease in lignin content causes severe reductions in mechanical properties. Changes in lignin structure, either from an increased S/G ratio or structural lignin modifications, also negatively influence the mechanical properties.

Epoxy-based nanocomposites were prepared by incorporating 0.3%, 0.5%, 0.7%, 1%, and 2% cellulose nanofibers (CNF) through a hand lay-up technique. The influence of the CNF as a reinforcement material on the morphology, and the physical, mechanical, and thermal properties of epoxy-based nanocomposites were investigated using scanning electron microscopy (SEM), density, void content, water absorption, tensile, flexural, impact strength, and thermogravimetric analyses. Compatibility between the nano-reinforcement and epoxy matrix was confirmed using SEM, which demonstrated that the CNF was homogeneously dispersed throughout the epoxy matrix. The mechanical properties were enhanced by increasing the CNF loading up to 1%. Moreover, the incorporation of CNF into the composites reduced the water uptake of the substrates in the water absorption test and resulted in a high thermal stability when exposed to a high temperature. Bamboo-CNF could be used as a potential reinforcement material to improve the properties of epoxy-based nanocomposites.

Properties were evaluated for heat-treated yellow poplar (Liriodendron tulipifera), eastern redcedar (Juniperus virginiana), and southern pine (Pinus echinata) samples. Differences in discoloration, surface roughness, and hardness of the samples as a function of heat exposure were tested at temperature levels of 130 °C, 160 °C, and 190 °C. The experiments were carried out on defect-free eastern redcedar, yellow poplar, and southern pine samples with dimensions of 50 cm by 4 cm by 2 cm (longitudinal, radial, tangential) supplied by a local sawmill. A total of 80 samples, 20 for each temperature level, were used for the tests. Based on the findings, it appears that eastern redcedar specimens had the least discoloration values as compared to those of two other types of wood. In all cases, hardness values of the samples showed adverse influence of heat exposure. It seems that as temperature level increased, the surface quality of the samples from all three species was enhanced. All types of samples had significant discoloration as a result of heat treatment, and such findings were more prominent in the case of both pine and yellow poplar specimens. Overall hardness characteristics of the samples were adversely influenced due to heat exposure.

This study aimed to screen high-performance flocculant-producing bacteria for flocculating suspended matter in wheat distillery wastewater. After the preliminary and secondary screening, a high-performance flocculant-producing bacteria strain was screened from the activated sludge of wheat distillery wastewater. Single factor and orthogonal experiments were used to optimize the culture and flocculent conditions for the flocculant-producing bacteria. A superior strain of Klebsiella M1 was screened and identified by 16S rDNA. The initial flocculating degree was up to 72%. Based on single-factor tests, the optimum flocculent conditions were a resting time of 30 min, 8%(v/v) culture medium dosage, and 3%(v/v) CaCl2. The optimum culture conditions were an incubation temperature of 30 °C for 48 h at pH 4.5 and rotation speed of 150 rpm. Under the optimum conditions, the flocculating degree was up to 82%. The best fermentation medium components were 15 g/L glucose, 2 g/L peptone, 1 g/L KH2PO4, and 2.5 g/L K2HPO4. A high flocculating degree was also achieved with the low-cost medium. The Klebsiella M1 bacteria strain can be used as a good bioflocculant produced bacteria for wheat distillery wastewater.