Volume 8 Issue 1

Co-firing ramie residue with coal was carried out in a thermogravimetric analyzer and a cyclone furnace to evaluate the effects of coal fraction (0 to 30 wt. %) on combustion performance. Thermogravimetric analysis (TGA) results showed that devolatilisation was the predominant process when the coal percentage in the blend was below 30 wt. %. For pure biomass firing in the cyclone furnace, an optimum equivalence ratio (ER =1.16) was found. Coal additions (0 to 30 wt. %) led to less slagging/fouling problems, higher combustion temperature and higher combustion efficiency along with low pollutant emissions, while the improvement in combustion temperature was weakened as the coal blend ratio exceeded 20 wt.%. The maximum temperature in the cyclone furnace increased from 1215 to 1319°C as the coal fraction increased from 0 to 30 wt.%.

Ultrasonic energy was applied to assist the wood vacuum drying process. At a drying temperature of 60°C, the absolute pressure was either 0.05 MPa or 0.08 MPa; the ultrasonic power and frequency were 100 W and 28 kHz, respectively. The results showed that the effective water diffusivity of the specimens dried by the ultrasonic assisted vacuum drying at 0.05 MPa or 0.08 MPa were higher than that of the samples dried without ultrasound. The ultrasound-vacuum drying rate was much faster than that of drying without ultrasound, especially for wood with a moisture content above the fiber saturation point. Drying at the absolute pressure of 0.05 MPa was faster than that of 0.08 MPa. Ultrasound-assisted drying was especially more beneficial when removing free water. The ultrasound-vacuum drying method could be applied in the wood drying industry as a means of saving energy and minimizing product quality damage.

This work focused on providing a molecular understanding of the way the polymeric properties of kraft lignin and its derivatives are affected by various thermal treatments. This information was then correlated with the polymeric properties of the materials (glass transition temperature (Tg), molecular weight characteristics, and thermal stability) for a series of selectively and progressively derivatized softwood kraft lignin samples. Softwood kraft lignin was highly susceptible to thermally induced reactions that caused its molecular characteristics to be severely altered with the concomitant formation of irreversible cross-linking. However, by fully methylating the phenolic OH groups from within the structure of softwood kraft lignin, the thermal stability of these materials was dramatically enhanced and their Tg reduced. While optimum thermal stability and melt re-cycling was observed with the fully methylated derivatives, fully oxypropylated phenolic substitution did not offer the same possibilities. The accumulated data is aimed at providing the foundations for a rational design of single component, lignin-based thermoplastic materials with reproducible polymeric properties when thermally processed in a number of manufacturing cycles.

Chemo-enzymatic functionalization offers an innovative approach to produce paper and board products with enhanced performance. Unbleached softwood kraft pulps were functionalized by laccase with methyl syringate(MS), p-hydroxybenzoic acid(HBA), gallic acid(GA), and syringaldehyde(SyA). The wet strength of fibers treated with MS and SyA increased by 57.9% and 31.9%, respectively. The dry strength of fibers treated with HBA, GA, and SyA increased from about 64 N·m/g to 68 N·m/g. The opacity of MS-treated fibers was the highest, and the surface lignin coverage increased. The kappa number and surface lignin of HBA-treated fibers changed little; however, the total carboxyl group significantly increased. The participation of phenolic compounds enhanced the reactivity of fibers to laccase in varying degree. However, the reactivity of phenols to laccase did not show a direct relation to the paper strength. All treatments with phenols decreased the brightness and the curl index of fibers. The syringyl-type phenols with hydrophobic groups (OCH3) were shown to be effective for improving the pulp wet strength. The compounds with carboxyl groups enhanced the pulp dry-strength. The observed pulp strength improvement could be attributed to the formation of covalent bonding via radical coupling, the attachment of the functional group, increased bonding area, and fiber entanglement.

Heat treatment under controlled temperatures can help enhance bamboo’s durability and dimensional stability. The treatment may simultaneously affect thermal and mechanical performance of bamboo fibers (BFs). The aim of this work was to study the effect of heat treating temperature on thermal decomposition kinetic properties of heat-treated BFs and resulting polymer composites using dynamic thermo-gravimetric analysis under nitrogen. Degradation models including the Kissinger and the Flynn-Wall-Ozawa methods were used to determine the apparent activation energy (Ea) of various materials. The results indicated that the thermal decomposition of the heat-treated BFs mainly occurred within a temperature range between 245°C and 354°C. The values of Ea varied from 161 to 177 kJ/mol and increased with increased heat treating temperatures for the fibers. The thermal decomposition of the heat-treated BF and high density polyethylene blends mainly occurred within a temperature range of 307°C and 483°C. The values of Ea were between 225 and 236 kJ/mol and decreased with the increase of fiber heat-treating temperatures. The established thermal decomposition kinetic parameters can help aid the development of polymer composites from heat-treated bamboo materials.

The effect of zinc borate (ZB) treatment on the mechanical and morphological properties of wood flour/polypropylene composites was investigated. Wood flour was first treated with ZB solution (1% w/w in ethanol-distilled water), followed by 24 hours of soaking on an unheated magnetic stirrer hot plate until relatively complete saturation was reached. Then, composites based on ZB-pretreated, ZB-treated-during-manufacturing, and untreated wood flour, polypropylene and coupling agent were made by melt compounding and then injection molding. The ZB treatment had no significant influence on mechanical properties of the composite with the exception of tensile strength. The composite made with ZB-pretreated wood flour exhibited the same mechanical properties as the composites made with ZB-in-process-treated wood flour; however there were statistically significant differences between flexural modulus and tensile strength of ZB-pretreated composites and ZB-in-process treated ones. Specimens containing the ZB showed lower flexural, tensile, and impact strength compared with the untreated specimens. However, the zinc borate treatments produced modest improvements in hardness performance. The SEM micrographs revealed that the outer surface of the wood fibers was coated by some crystalline deposits of zinc borate.

The objective of this study was to investigate the deformation behavior and damage model of bamboo bundle corrugated laminated composites under low velocity impact loading. The influence of different stacking sequences, i.e., bamboo bundle parallel to the corrugated waves (type I), cross-ply (type II), and perpendicular to the waves (type III), in laminates was studied in regard to impact loading. A shape parameter, K, was developed to quantify the effect of corrugation on impact response. The results of this study indicated that the type I composites displayed the optimum impact performance, followed by types II and III. The total energy absorbed by the type I laminates was 1.3 and 2.2 times as much as types II and III . The values of peak load were type I > type II > type III. The composites deformed and failed in different manners under low velocity impact loading: material failure, delamination and fiber tensile fracture, and structural collapse were the main modes of failure for type I, II, and III, respectively. The effect of the corrugated shape on impact properties of composites was positive for type I, but negative for type II composites.

This study focused on cellulose nanowhiskers (CNWs) isolation using a combination of acid hydrolysis and high pressure homogenization, and investigated the effects of acid concentration (20, 40, and 60 wt%), hydrolysis temperature (20, 40, and 60 oC), and hydrolysis time (2, 4, and 6 h) on the geometry and chemical properties. After the combined treatment, nanoparticles were rodlike with a diameter of 11 to 33 nm, a length of 199 to 344 nm, and aspect ratio of 10 to 18, which are characteristic properties of CNWs. Fourier transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS) analyses showed that some breakages of intramolecular hydrogen bonds and glycosidic bonds occurred during the hydrolysis reaction of MCC. An increase in acid concentration from 20 to 60 wt% could effectively accelerate these breakages in cellulose molecules, leading to narrower, less polydisperse nanowhiskers with lower crystallinity.

There is an increasing demand for green chemistry technologies that can cope with environmental waste management challenges. Agro-industrial residues are primarily composed of complex polysaccharides that support microbial growth for the production of industrially important enzymes such as ligninolytic enzymes. Schyzophyllum commune and Ganoderma lucidum were used alone, as well as mixed/co-culture, to produce crude ligninolytic enzymes extracts using corn stover and banana stalk as a substrate during solid state fermentation (SSF). In the initial screening, the extracted ligninolytic enzymes from S. commune produced using corn stover as the substrate showed higher activities of lignin peroxidase (1007.39 U/mL), manganese peroxidase (614.23 U/mL), and laccase (97.47 U/mL) as compared to G. lucidum and the mixed culture. To improve the production of ligninolytic enzymes by S. commune with solid state fermentation (SSF), physical factors such as pH, temperature, moisture, inoculum size, and incubation time were optimized by varying them simultaneously using response surface methodology (RSM) with a central composite design (CCD). The optimum SSF conditions were (for a 5 g corn stover substrate size): pH = 4.5; temperature = 35°C; inoculum size = 4 mL; and moisture content = 60%. Under optimum conditions, the activities of lignin peroxidase (LiP), manganese peroxidase (MnP), and laccase were 1270.40, 715.08, and 130.80 IU/mL, respectively.

The aim of this work was to develop a suitable bioprocess to maximize productionof second generation bio-ethanol in submerged fermentation by using fermentable sugars derived from oil palm frond (OPF) through the solid state fermentation (SSF) system. The strain Saccharomyces cerevisiae was selected, and fermentation conditions were refined at the laboratory scale. Following optimization of inoculums size of S. cerevisiae and concentration of fermentable sugars (growth medium), yields of ethanol production as high as 23.10 g/ L were obtained, compared to 5.61 g/L before optimization. S. cerevisiae cells were able to assimilate the majority of the fermentable sugars from OPF. The results demonstrated that the culture conditions in fermentation process can significantly influence the ethanol yield in the flask system by using fermentable sugars obtained from the enzyme hydrolysis of OPF as fermentation medium.