Research Articles

The aim of this study was to evaluate the effect of the grades of cellulose nanofibril (CNF) on the strength and drainage of security paper made from cotton lint mixed pulp (CLMP). Refined CNF (RE-CNF), enzymatic CNF (EN-CNF), and carboxymethylated CNF (CM-CNF) were prepared, and their characteristics were analyzed. Handsheets were made via the addition of three CNFs into CLMP furnish, and their physical properties were measured. The drainability of the CLMP in the presence of CNFs was also determined depending on the grades and the dosage of the CNFs. The CM-CNF was the most effective at enhancing tensile strength by 50%, folding endurance by 464%, and sheet density by 10% when 5% of CM-CNF was added in the CLMP furnish. Moreover, 5% of EN-CNF improved tensile strength by 30% and folding endurance by 156%, but it was less effective as a paper strength promotor than CM-CNF and RE-CNF. A dramatic drainage reduction by 34% was observed when 5% of CM-CNF was added into the CLMP furnish, and EN-CNF presented the highest drainage rate. A high dosage of CNFs deteriorated the furnish drainage and promoted the strength. Therefore, papermakers should select the proper grade and the dosage of CNF for the manufacture of high-strength security paper.

Screw withdrawal and flexural strength were evaluated for Dendrocalamus asper and Gigantochloa levis bamboo species to explore the possibility of their use as structural material in place of wood. Dry bamboo strips and 4-mm-thick oil palm trunk veneer (OPTV) were processed into thin laminates and hot-pressed using urea formaldehyde resin to produce bamboo-OPTV hybrid biocomposites. Bamboo furniture is far more resistant to damage than traditional hardwoods. Bamboo is even used in cutting boards for this reason. Even though there have been some reports on the mechanical enhancement of the bamboo-based composites, so far there has been no comprehensive study on the screw pulling and flexural strength of bamboo-based hybrid composites. The results revealed a stronger correlation of the bamboo hybrid under screw withdrawal and flexural strength, but there was a weaker correlation in the mechanical properties of the bamboo hybrid due to the random selection of laminate from different bamboo species. Furthermore, test results clearly showed that bamboo-OPTV hybrid biocomposites can be used as an alternative to wood and wood-based composites for furniture applications.

Black poplar (Populus nigra L.) was subjected to thermal modification in superheated steam. The modification was performed at 160 °C, 190 °C, and 220 °C for 2 h. The equilibrium moisture content of the black poplar wood was examined when it was exposed to 76% ± 2% relative humidity at a temperature of 20 °C ± 2 °C. The thermal modification of the poplar wood changed its moisture-exchange-related physical properties to a large extent. The effects of temperature on individual properties (density, mass loss, hygroscopicity, swelling, and water absorption) were diverse, and the intensity of these effects increased with increasing temperature of the thermal treatment process. In most cases, no significant differences were observed between the changes in properties of the sapwood and the heartwood.

Anaerobic digestion of biomass wastes could have a huge impact on renewable energy requirements. Moreover, it reduces biomass wastes and greenhouse gas emissions. To improve the performance of anaerobic digesters, the co-digestion of different biomass wastes, such as waste activated sludge, microalgae, and agriculture wastes including sawdust, wheat straw, and rice straw has been performed in this study. The results showed that sludge and microalgae have low carbon/nitrogen (C/N) ratios. Meanwhile, the addition of agriculture wastes to sludge and microalgae mixture increased the C/N ratio and improved biogas yield by 179%, 209%, and 265% in the cases of adding sawdust, rice straw, and wheat straw, respectively. Co-digestion with wheat straw showed the highest values of C/N for the feedstock (20.6) and biogas production. Moreover, it recorded the highest reduction values for total solids (48.1%), volatile solids (58.2%), and chemical oxygen demand (77.5%) as compared to the other wastes.

Corncob cellulose from residue of saccharified agricultural waste corncob was used as a new resource of cellulose to dissolve in 1-allyl-3-methylimidazolium chloride (AmimCl) and then to regenerate in three different coagulation baths: water, 60 wt% AmimCl aqueous solution, and anhydrous ethanol. The effects of the different coagulation baths on the properties of corncob cellulose aerogels and regenerated films were studied. The results showed that the aerogels had porous network structures, and the regenerated films were relatively transparent with high strengths and good thermal stabilities. When 60 wt% AmimCl was used as the coagulation bath, the network of the obtained aerogel was dense and uniform, and the regenerated film had good thermal stability and a tensile strength superior to the films from the other regeneration baths. The films might have uses in packaging or other fields and aid in comprehensive utilization of agricultural wastes.

Mechanical and waterproof properties were evaluated for hot-pressed cotton boards produced from different layers (3, 4, and 5) of cotton veneers under the same weight of cotton fibers and melamine-urea-formaldehyde adhesive. The mechanical and waterproof properties of cotton boards exceeded the specifications for particleboard and medium-density fiberboard of the China national standard requirements, and the four-layer cotton boards performed better. Scanning electron microscopy images showed that fibers were intertwined to form a dense network structure after hot-pressing with water, and thicker veneers were not conducive to the penetration of adhesives after cold-pressing. Fourier transform infrared spectra indicated that hydrogen bonding, physical, and mechanical bonding took place in the cotton veneers, and stronger absorption peaks were shown for the chemical functional groups of the five-layer and four-layer cotton boards. X-ray diffraction spectra revealed that the cellulose crystallinity of the cotton boards (3, 4, and 5 layers) increased to 74.5%, 74.4%, and 73.2%, respectively. Thermal gravity/ differential thermal gravity curves showed that the thinner cotton veneers of the cotton boards showed better thermal stability. These results showed promise for the revaluation of this textile waste to produce biomass composites and for its potential use as a raw material in the preparation of biomass composites.

In biomechanical analyses, computational models are essential tools for simulating the behavior of a tree subjected to a load. However, such models allow only approximation of the actual behavior of the tree if the elastic parameters of the wood in different tree parts (stem, branches, and roots) and at least orthotropic behavior are not considered. In addition, as the wood is green, the parameters of strength and stiffness must be adequate for this level of moisture. However, even for stem wood, knowledge of elastic properties is not available for most species used in urban tree planting, and this scarcity of information is even greater for wood branches. The objective of this research was to evaluate methodology, based on wave propagation, in characterizing the 12 elastic constants of wood from branches. Complementarily, compression tests were performed to characterize the strength. The obtained elastic parameters using ultrasound tests were comparable with the values expected based on theoretical aspects related to the behavior of the wood. The results of the compression test complemented the ultrasound characterization, but the application of this method for the complete characterization of the elastic parameters is not feasible for tree branches because of their small size.

Cellulose was extracted from corn stalk pith (CSP) and used for fabricating hybrid composite films with acceptable physical properties. As reinforced additives, low contents of graphene oxide (GO) and black phosphorene (BP), both ranging from 0.05 to 0.15 wt%, were separately incorporated into the cellulose matrix in a ZnCl2 aqueous system. A series of the composites were prepared via a regeneration process. The as-prepared composites showed various properties depending largely on the additive content, manner of processing, and the type of additive used. GO and BP nanosheets were homogeneously dispersed in the regenerated cellulose (RC), smoothly forming the dense films. Crystalline structures of RC-based films were revealed to be cellulose-II, and in addition to GO-crosslinked RC samples (RC-GO), an increase in the additive dosage led to a decrement in the crystallinity index of blended films (RC/GO and RC/BP). At 0.15 wt% additive amount, the RC-GO possessed superior thermal stability, tensile strength, and Young’s modulus, increasing 7.8%, 190.2%, and 79.0%, respectively, while the RC/BP exhibited a 3.5 times improvement in the elongation at break.

With the ever-increasing usage of recycled fibers, dry-strength agents play an increasingly important role in the papermaking industry. In this study, a new kind of dry-strength agent (CMS-g-PAM) was developed via grafting polyacrylamide onto carboxymethyl starch (CMS). Effects of the operation conditions, including the CMS-g-PAM dosage, polyaluminium chloride (PAC) dosage, and pH value of pulp system, on the properties of the paper were investigated. The contrasting effects when comparing the CMS-g-PAM and CMS were also researched. The results indicated that CMS-g-PAM had a beneficial effect on the paper properties. Compared to the control sample, when 1% CMS-g-PAM was added, the tensile index, burst index, and folding endurance of handsheets displayed noticeable increases of 38.2%, 34.7%, and 97.7%, respectively, and these properties were increased by 27.4%, 17.2%, and 46.6% when compared with the CMS-treated sample of this addition level. Scanning electron microscopy images showed that the bonding between fibers of the paper became tighter after using the CMS-g-PAM. The results demonstrated that CMS-g-PAM can be used as an effective dry-strength agent.

Wood-plastic composites for 3D printing from plant fiber (bleached pulp powder, mechanical pulp powder, newspaper pulp powder, eucalyptus powder, pine powder, and lignin) and polylactic acid (PLA), with silane coupling agent (KH550) as plasticizer, were prepared via melt extrusion. The physical properties, such as surface morphology, apparent density, tensile strength, melt flow rate, compatibility, and thermal stability were measured. Moreover, the effects of the content of various types of plant fiber powder in PLA on the properties of the prepared composites were investigated. The results showed that the modified lignin/PLA composite exhibited a superior performance under the same added amount. In particular, when the amount of lignin added was 15%, the tensile strength of the composite was 74.0% higher than that of pure PLA, and the melt flow rate was reduced by 17.8% compared with pure PLA. The density of the composite increased 15.8% compared with pure PLA when the lignin content was 20%. The scanning electron microscopy cross-sectional morphology and differential scanning calorimetry analyses showed that the optimal addition amount of lignin was 15%. Finally, the prepared lignin/PLA composite material was used in 3D printing with a smooth silky property and an excellent printing performance.