Research Articles

Nanoparticles are widely used in the papermaking industry as retention/ drainage aids, usually in conjunction with a high mass cationic polyelectrolyte such as cationic starch. However, little convincing knowledge of their role and mechanism in the wet-end system is yet found. This work focused on the role of nanosilica on papermaking wet end system in response to some processing parameters (drainage, retention, and electrostatic force of the whole system). The observations indicated that the nanosilica performance is defined by interactions of nanosilica with the complex aqueous environment of wet end system. The interaction mechanism seems to rely on introduction of nanoparticles into a cationic starch-fines-fibers network, converting the fiber mat on the forming wire into a porous structure that is responsive to retention and drainage.

The anatomical, chemical, and physico-mechanical properties of the fibres of C. pangorei were investigated in this study. The results indicate that the rind region that is split and used in mat making contains compactly arranged fibrovascular bundles and a discontinuous patch of fibrous sheath. The frequency and the R/T ratio of the bundles were high in the rind region and were indicative of fibre strength. Lignin and cellulose, the major cell wall substances, were localized with heterochromatic, fluorescent, and natural dyes. The holocellulose content was high (82.2 %), and the lignin content was comparatively low (13.28 %) as analyzed by the method of Doree. Very thick walled, thick walled, very thin walled, and thin walled fibres were characterized when fibres were macerated, and their derived values indicated a high Slenderness and Runkell ratio that is indicative of tear resistance. The tenacity and percentage elongation of the split culm strands was also high, and this implies high strength of the fibre strands. The fibre of this mat sedge thus has favorable characteristics to be potentially utilized in the mat and silkmat industry. Furthermore the plant’s annual harvesting period, biomass, and appropriate fibre characteristics makes this sedge very attractive as an alternative fibre source in the miscellaneous plant fibre industry.

The objectives of this research were to investigate surface characteristics and overlaying properties of medium density fiberboard (MDF) panels, as affected by thermal treatment of the fibers. MDF panels were manufactured from untreated rubberwood fibers and fibers treated at three different temperatures (120, 150, or 180°C) for 15 or 30 min. Contact angle measurements were obtained by using a goniometer connected with a digital camera and computer system. Roughness measurements, average roughness (Ra), mean peak-to-valley height (Rz), and maximum roughness (Ry), were taken from the sanded samples along and across the sandmarks using a fine stylus tracing technique. With the increasing thermal treatment temperature and time of the fibers, surface roughness of the panels decreased, while their wettability and adhesive bonding strength decreased. Statistical analyses showed significant differences in the surface roughness, contact angle, and adhesive bonding strength of the panels following thermal treatment. Based on the findings obtained from this study, the contact angle and surface roughness parameters of the MDF panels made from thermally treated rubberwood fibers can provide a good information on their ability to bond.

Phase transformations in microcrystalline cellulose (MCC) were studied following dissolution of 5, 10, and 20 wt. % MCC in the ionic liquid 1-butyl-3-methylimidazolium formate (BMIMFmO) and regeneration via water. BMIMFmO was found to be useful as a non-derivatizing solvent for cellulose without the need for any pre-treatment. Wide angle X-ray scattering indicated that a phase transformation from cellulose I to either a poorly crystalline form of cellulose I and/or cellulose II occurs during regeneration after dissolution in BMIMFmO. The dissolution time affected the resulting microstructure of the regenerated cellulose. Thermogravi-metric analysis showed that regeneration from the ionic liquid lowers the decomposition onset temperature and increases the char yield when compared with the as-received MCC.

Corn stover and rice straw lignin samples received from ethanol pilot plants, along with softwood kraft lignin samples, were characterized using pyrolysis GC-MS, 13C CP/MAS NMR spectroscopy, and permanganate oxidation degradation. The lignins were then esterified using 1-methylimidazole as a catalyst in a pyridine-free reaction, and the thermal properties of the products were evaluated. Solid state NMR showed the rice straw lignin contained 18% residual polysaccharides. Pyrolysis GC-MS showed the softwood kraft, corn stover, and rice straw lignins to be G – type, H/G/S – type, and G/S – type, respectively. However, some discrepancy was apparent between the pyrolysis and permanganate oxidation studies as to the ratios of the monomeric make-up of the lignins. The kraft and rice straw lignins were determined to have high degrees of condensation, while the corn stover lignin was uncondensed. Little to no increase in solubility was noticed for corn stover or rice straw lignin esters in organic solvents. Glass transition temperatures (Tg) of the lignin derivatives were determined by a combination of differential scanning calorimetry, dynamic mechanical analysis, and parallel plate rheometry.

In recent years, increasing attention has been directed to the use of renewable resources, particularly of sugarcane bagasse. Considering the abundant availability of such lignocellulosic materials, relatively few attempts have been made regarding their utilization. Studies about properties and morphology, heavy metal adsorption, and membranes preparation have been conduced by this research group in order to use these materials. In this paper, cellulose fibers obtained from sugarcane bagasse were bleached and modified by hydrous niobium phosphate. Hybrids (cellulose/NbOPO4.nH2O) were prepared from metallic niobium dissolved in a fluoridric/nitric (10:1) mixture, to which cellulose sugarcane bagasse was added. Afterwards a concentrated orthophosphoric acid (85mL, 85% w/w) was added to precipitate hydrous niobium phosphate particles. This material was characterized by X-ray diffraction (XRD), thermogravimetry (TG/DTG), and differential scanning calorimetry (DSC) analyses, as well as scanning electronic microscopy (SEM) coupled to an energy dispersive spectrophotometer (EDS). Morphological studies of bleached cellulose revealed different sizes and arrangement of cells, showing that NbOPO4.nH2O was present in the cellulose structure. Thermal stability of the hybrid was observed up to approximately 200°C, and the cellulose decomposed at 300°C. These data will help finding new uses for these materials.

Malaysia, especially the Borneo Island state of Sarawak, has a large variety of tropical wood species. In this study, selected raw tropical wood species namely Artocarpus Elasticus, Artocarpus Rigidus, Xylopia spp., Koompassia Malaccensis, and Eugenia spp. were chemically treated with sodium metaperiodate to convert them into plasticized wood (PW). Manufactured plasticized wood samples were characterized using, Fourier transform infrared spectroscopy, scanning electron microscopy, and mechanical testing (modulus of elasticity (MOE), modulus of rupture (MOR), static Young’s modulus (Es), decay resistance, and water absorption). MOE and MOR were calculated using a three-point bending test. Es and decay resistance were calculated using the compression parallel to grain test and the natural laboratory decay test, respectively. The manufactured PW yielded higher MOE, MOR, and Es. PW had a lower water content compared to the untreated wood and had high resistance to decay exposure, with Eugenia spp. having the highest resistance compared to the others.

The cell wall of most plant biomass from forest and agricultural resources consists of three major polymers, cellulose, hemicellulose, and lignin. Of these, hemicelluloses have gained increasing attention as sustainable raw materials. In this study, novel pH-sensitive semi-IPN hydrogels based on hemicelluloses and chitosan were prepared using glutaraldehyde as the crosslinking agent. The hemicellulose isolated from aspen was analyzed for sugar content by HPLC, and its molecular weight distribution was determined by high performance size exclusion chromatography. Results revealed that hemicellulose had a broad molecular weight distribution with a fair amount of polymeric units, together with xylose, arabinose, and glucose. The effects of hemicellulose content on mechanical properties and swelling behavior of hydrogels were investigated. The semi-IPNs hydrogel structure was confirmed by FT-IR, X-ray study, and the ninhydrin assay method. X-ray analysis showed that higher hemicellulose contents yielded higher crystallinity. Mechanical properties were mainly dependent on the crosslink density and average molecular weight between crosslinks. Swelling ratios increased with increasing hemicellulose content and were high at low pH values due to repulsion between similarly charged groups. In vitro release study of a model drug showed that these semi-IPN hydrogels could be used for controlled drug delivery into gastric fluid.

The present study deals with the surface modification of Agave americana L. fiber through graft copolymerization of methyl methacrylate under pressure in the presence of ceric ammonium nitrate as redox initiator. The various reaction parameters such as reaction time, pressure, concentration of nitric acid, initiator, and monomer, etc. were optimized to have the maximum graft yield of 13.6%. The grafted fibers were then subjected to the evaluation of different physico-chemical properties such as swelling behavior, solubility, moisture absorption under different humidity levels, resistance to acids and bases, etc. It was observed that swelling behavior, solubility behavior, and moisture absorbance decreased with increase in grafting, whereas resistance to acids and bases increased with grafting. The fibers grafted under the optimized conditions were then characterized by Fourier transform infra-red spectroscopy, scanning electron microscopy, thermogravimetric analysis, and x-ray diffraction techniques.

The objective of this study is to evaluate the effect of décor paper and resin type on physical properties, mechanic properties, and surface quality properties of particleboards coated with décor papers impregnated by using different resin. White oak, New wenge and common maple pattern decor papers impregnated with urea formaldehyde (UF), melamine formaldehyde (MF) and urea-melamine formaldehyde (UF+MF) were used as coating materials. Particleboard surface was laminated with these coating materials by hydraulic press. As a result, specimens coated with MF-impregnated papers showed better performance than those coated with UF and UF+MF-impregnated papers. Resin type and paper pattern affected the physical, mechanical (with exception of tension strength), and surface properties (especially cigarette burn and abrasion) of coated particleboards. Physical and mechanical properties of coated particleboard were significantly improved compared to non-laminated particleboards. It was found that paper pattern affected the surface properties, such as impact, scratch, and abrasion, resistance to staining and cigarette burn. However, it did not change the cracking and steaming properties of the coated samples. After the coating process, it was determined that cigarette burn, abrasion, impact, and scratch performances were among 1 to 3 grade, lp:10-35, Fp:210-340/100-150, and 2 to 5 grade, respectively.