Research Articles

The ability to increase the filler content of paper without significantly sacrificing its mechanical strength is of high interest for papermakers. In this work, three samples of ground calcium carbonate (GCC), differing in size and in brightness, modified with silica via the sol-gel method, were used as fillers in papermaking. Handsheets were produced using a eucalyptus kraft pulp furnish and with a filler amount near 20%. It was found that not only were the strength properties of the handsheets produced with the modified GCCs always significantly better than those obtained with the unmodified GCCs (e.g., the tensile index exhibited improvements of 16 to 20%), but bulk also was increased (by 7 to 13%). Some decreases in the light scattering and opacity values were noted when using the modified GCC, but the brightness was roughly the same. The enhanced fiber-to-filler bonding may be attributed to the hydrogen bonding between the cellulosic fibers and the hydroxyl groups of the silica coating the calcium carbonate particles.

Reducing the consumption of phenol during synthesis of phenolic resins is of great technological and scientific interest because of its economic and environmental implications. In this work, the use of hydroxymethylated lignins as a partial replacement for phenol in resol phenol-formaldehyde resins used for the production of decorative laminates was experimentally studied. The work involved: i) the industrial synthesis of traditional and modified resols with 10%w/w of sodium lignosulfonate and kraft-type lignin; ii) the industrial impregnation of kraft-type paper with the produced resins; iii) the production of laminates on both laboratory and industrial scales; and iv) the measurement of their final properties. The mechanical performance of the laminates was evaluated via the determination of the Young modulus, bending strength, biaxial impact strength, and Mode-I interlaminar fracture toughness. The (modified and traditional) laminates exhibited statistically significant differences in mechanical properties. However, the partial lignin replacement did not produce effects that were detrimental to the overall performance of the decorative laminates.

A novel crosslinked hydrogel was prepared from sodium carboxymethyl cellulose (CMC) and hydroxyethyl cellulose (HEC) using ammonium persulfate as an initiator and methylenebisacrylamide as a crosslinker for drug delivery. The chemical structure of the copolymer was characterized by Fourier transform infrared spectroscopy and X-ray diffraction, and the morphology was observed under scanning electron microscopy. The swelling behavior of the hydrogels confirmed the pH- and ionic strength-sensitivity. The reversibility of the hydrogels and the on-off switching behavior were also investigated, providing the potential for drug delivery. The release of bovine serum albumin (BSA) from drug-loaded hydrogels was studied at different pH conditions to simulate gastrointestinal conditions. The amount of BSA released from the hydrogels at pH 1.2 was relatively low (17.8%), while 85.2% was released at pH 7.4. According to the results, the CMC/HEC hydrogel has the potential for use in the controlled release of oral medication.

(NH4)2SO4 solution was employed to pre-treat regenerated cellulose fiber (from bamboo) using an ultrasonic method, and then the material was heat-treated at 250 °C. Scanning electron microscopy revealed that erosion and cracks of the fiber surface increased after being impregnated with (NH4)2SO4 combined with ultrasonic pretreatment. There was a small change in the intensity and the position of some peaks in the Fourier transform infrared spectra, and in the heat treatment, partial pyrolysis of the cellulose occurred. The data showed that for the cellulose fiber pretreated with 5 wt% (NH4)2SO4 the decomposition temperature shifted to the lower side (252 °C), and the decomposition range (180 °C to 454 °C) was wider than for the other impregnation fibers and reference. However, the rate of decomposition was different with different concentrations of (NH4)2SO4. The C content of heat-treated fiber with 5 wt% (NH4)2SO4 increased to 52%. The above results indicated that the (NH4)2SO4 was an effective catalyst to pretreat regenerated cellulose fiber in the pathway of pyrolysis.

This work focuses on the mechanical properties and solid particle impact behaviour of Luffa cylindrica fibre (LCF)-reinforced epoxy composites. Single (SL)-, double (DL)-, and triple (TL)-layered composites were prepared using the general hand lay-up technique. The erosive wear test was carried out using an air jet erosion tester according to the ASTM G76 standard. The erodent used was silica sand particles (200 ± 50 µm). The experimental parameters studied for the erosion rate of the LCF epoxy composites were impingement angle (30° to 90°) and particle velocity (48 m/s to 82 m/s). Analysis of the results revealed that at the peak erosion rate, semi ductile behaviour of the composite was apparent. Possible erosion mechanisms were discussed and were investigated using scanning electron microscopy (SEM).

Wood is a pure, sustainable, renewable material. The increasing use of wood for construction can improve its sustainability. There are various techniques to assemble multi-layer wooden panels into prefabricated, load-bearing construction elements. However, comparative market and economy studies are still scarce. In this study, the following assembling techniques were compared: laminating, nailing, stapling, screwing, stress laminating, doweling, dovetailing, and wood welding. The production costs, durability, and ecological considerations were presented. This study was based on reviews of published works and information gathered from 27 leading wood product manufacturing companies in six European countries. The study shows that the various techniques of assembling multi-layer wooden construction panel elements are very different. Cross laminated timber (CLT) exhibited the best results in terms of cost and durability. With regard to ecological concerns, dovetailing is the best. Taking into account both durability and ecological considerations, doweling is the best. These alternatives give manufacturers some freedom of choice regarding the visibility of surfaces and the efficient use of lower-quality timber. CLT is the most cost-effective, is not patented, and is a well-established option on the market today.

Flavonoids represent a large group of polyphenols that have been recognized to exert a wide range of biological effects, such as anticancer, inflammation inhibition, anti-aging, and neuroprotective activities. In the forest industry, tree twigs have been treated as residues; however, tree twigs could be a rich source of high-value added compounds, which have been relatively unexplored. In this study, an investigation into the chemical constituent of extractives from S. japonica twigsresulted in the isolation of a new (Z)-caffeoyl flavonol glycoside that was elucidated as myricetin 3-O-(4”-(Z)-caffeoyl)-α-rhamnopyranoside (IV). The structure of the new compound was established mostly on the basis of extensive spectroscopic techniques and other physiochemical evidences. Among the three known flavonoids extracted in this work, including isoquercitrin (I), isorhamnetin 3′-O–β-D-glucopyranoside (II), and myricitrin (III), II and III have never been previously reported in the Sophora genus.

This study outlines the results of a biobleaching study of acacia (A. mangium) and eucalyptus (E. globulus) hardwood kraft pulps with commercial xylanase (Optimase CX 72 L). The comparative study was carried out using an elemental chlorine-free (ECF) bleaching sequence (D0EPD1D2) after the enzyme (X) stage. The enzyme treatment resulted in improved optical properties with a reduction in bleach chemical consumption. At an equivalent bleach chemical consumption, a brightness gain of 2.1 and 1.7 units and a whiteness gain of 2.7 and 2.3 units were observed with xylanase treatment in acacia and eucalyptus pulps, respectively. In ECF bleaching using the D0EPD1D2 sequence, a final brightness was achieved to the extent of 90% ISO and 89% ISO for acacia and eucalyptus, respectively, at an equivalent charge of bleach chemicals. The post-color (PC) number was also reduced by up to 45% for both hardwood pulps compared with the control. The bleachability of acacia was observed to be significantly higher than that of eucalyptus. In addition, a 17.0% and 23.0% reduction in chlorine dioxide and sodium hydroxide, respectively, were obtained for both hardwood pulps after xylanase pre-bleaching, thus indicating an environmentally friendly approach to the process.

The effects of milling process parameters on cutting forces and surface roughness were studied during peripheral up milling of bamboo scrimber. The study results indicated that the effect of feed rate on cutting force components Fx, +Fy, –Fy, and surface roughness Ra were the most significant compared to spindle speed and cut depth during longitudinal milling. Fx, +Fy, –Fy, and Ra decreased slightly with increasing spindle speed, but increased greatly with increasing feed rate. In addition, cutting direction had a great effect on the cutting force components Fx and +Fy, as well as the machined surface roughness Ra. Fx, +Fy, and Ra during longitudinal cutting were always larger than those during end-grain cutting. Decreasing the feed rate appropriately could greatly improve the quality of the machined surface.

Crushing behaviors of luffa sponges were studied through mechanical experiments. Controlled by four-order hierarchical and anisotropic structures, luffa sponges exhibit anisotropic responses along axial, radial, and circumferential directions. The ultra-thin but stiff inner surface layer dominates the crushing behavior, endowing the axially compressed luffa cylinder with structural integrity, enhancing the elastic deformation and yielding strength. In radial, circumferential, and lateral compressions, after removing the inner surface layer, luffa sponges are compliant and have large quasi-linear deformation before densification, without a plateau characterized by yielding and deformation. Immersed into water, crushed luffa sponge cylinders recover their geometry completely. However, compression strength is only partially restored. Gradual damage of the inner surface layer in water immersing/drying cycles greatly weakens the compression strength. In the case of removal of the inner surface layer, crushed luffa sponge cylinders completely restore their quasi-linear deformation ability during the water immersing/drying cycles.