Journal of Lignocellulose
Volume:1 Issue: 2, 2012

We have traditionally used as much wood as we do food, and nowadays the wood supply coming mostly from natural forests is becoming limiting. However, there are energy-efficient and environmentally acceptable substitutes in the form of “non-woods” that could replace wood. There are some likely means that we can employ to satisfy the increasing wood and paper industries demand with nonwoods; however, several considerations should be taken into account when planning for future raw materials supply strategies.

In this research, the effects of combining white birch species with hornbeam and beech on the strength properties and fiber length distribution of the CMP pulp in Mazandaran Wood and Paper Industries (MWPI), was investigated. CMP pulp was prepared based on the conditions of liquor to wood ratio: 7/1, sodium sulfite: 20% based on OD wood chips, temperature: 160 °C and cooking time: 85 to 135 minutes to achieve CMP pulp yield of 85 % by using imported birch at 10, 20, 30, and 40% in combination with 60 to 90% hornbeam and beech. CMP pulp in MWPI was produced using 75% hornbeam and 25% beech under similar conditions. After defibration of cooked wood chips in a 20-inch defibrator, it was refined by PFI mill refiner up to the freeness of 300 mL CSF. The results of the standard handsheet analysis showed that using 10 to 40% birch species resulted in a significant reduction of pulp shives (0.36%), higher long fibers fraction increase of medium fiber (59.9%), as well as short fibers (16.3%) and reduction of fines (9.8%) fractions in pulp furnish, as compared with CMP pulp from MWPI. In addition, using different percentages of birch in combination with hornbeam and beech resulted in improving the paper's strength properties such as tensile index (69.4 Nm/g), burst index (582.4 kPa.m2/g), tear index (16.6 mN.m2/g), and stiffness (36.7 mN) as compared to MWPI's CMP pulp.

Cement-based composites were prepared from rice husk and styreneacrylic emulsion (SAE) with a semi-dry production process. The dosage of SAE, the rice husk content, and alkali treatment on the mechanical properties of the composites were studied. The mechanical test of the rice-husk cement composites proved that SAE is an effective additive for reinforcing the composites, and the mechanical properties improved significantly by alkali treatment and adding SAE. The composites were characterized by FT-IR, SEM, and XRD. The results indicated that SAE can be beneficial for the hydration of the composites.

In this research, specific dynamic shear moduli in plane with LR and LT surface of 22 rectangular clear beams of beech wood (Fagus orientalis) were evaluated in “free flexural vibration of a free-free bar” method with and without the presence of drilled holes on the tangential surface. The drilling was done exactly at the middle of the bar, on the node of the 2nd mode of vibration. Stepwise hole widening from zero to 3, 5, 8, and 10 mm, visible on two opposite tangential surfaces were used. Beech timbers were converted to nominal dimensions of 20×20×360 mm R×T×L. After measuring the dimensions and calculating the density () of the specimens, for both radial and tangential impacts of hammer in which the beam was vibrated in LT and LR plane, respectively, two specific shear moduli (specific GLR and specific GLT) were evaluated in Timoshenko beam theory, considering the three initial modes of vibration. When the bar was excited from its tangential surface by a percussion (vibrated in LR plane), stepwise drilling raised the estimated value for specific shear modulus in LR plane (Specific GLR). However, in LT vibrations, the specific GLT remained statistically constant. It is clear that the specific shear moduli as material property are not affected by artificial manipulation, but the responses of the bars would be affected. So the obtained result has been discussed due to neutral axis related to the hole localization. The finding of this paper may be used as an indicator for recognition of a hidden hole, perpendicular to the growth rings.

In this study, sawn pieces of Larix gmelinii lumber were dried, and the specimens were divided into six piles with the use of stickers having two thicknesses. The convection conditions were kept the same throughout the high-frequency heating in order to maintain the core surface temperature difference, while the high-frequency time was adjusted in order to meet the temperature difference requirements. Meanwhile, the variables of drying rate, energy consumption, and drying quality were compared for the 15- and 20 mm-thick stickers. The result was that the drying rate of the piles with 15 mm stickers was lower above the FSP (fiber saturation point), but began to converge near to the point of reaching the FSP. Moreover, at the end of the drying process, the drying rate of the piles with 15 mm thickness stickers was higher than, and the energy consumption and drying quality superior to, those with 20 mm thickness stickers.

In this study, finite element analysis was used to investigate the deflection, stiffness, and failure characteristics of case furniture. Tests were performed to evaluate the tensile stress distribution in screw joints under tensile load. To meet this objective, the effects of two screw diameters (4 and 5 mm) were studied using beech (Fagus orientalis), alder (Alnus subcordata), and white spruce (Picea Abies) wood species. The finite element analysis method (FEM) with ANSYS software was utilized to evaluate the distribution and concentration of stress in the joints, as well as variations of stress due to the mentioned variables. In order to perform the numerical computations, the T-shaped specimens had dimensions of 50 × 50 × 25 mm to meet EN 789 modified standard requirements, and the screw models had diameters of 4 and 5 mm, with a length of 50 mm. The results showed that stress concentration was between the screw threads. The stress in the joint model was less than that of the screw model. The larger screw diameter experienced a larger amount of stress but did not follow a constant trend, showing that screw diameter should be proportional to surface area. It was concluded that the finite element method is a suitable method with the use of exact numerical calculations to check the loads imposed on the structures. The FEM can be used as a suitable non-destructive technique for determining structural strength at various times.

Graft copolymerization of binary mixture of methyl methacrylate (MMA) and acrylonitrile (AN) has been carried out onto Agave americana fibers in the presence of Ce (IV) ions at 45.0 ± 0.1 0C. The addition of acrylonitrile as a comonomer has shown a significant increase in graft copolymerization of methyl methacrylate onto the lignocellulosic fibers. A synergistic effect of acrylonitrile on methyl methacrylate has been observed when graft copolymers were prepared using different feed compositions (fMMA) ranging from 0.2 to 0.8 at constant feed molarity of 5.0 x 10 -1 mol dm-3. The rate of grafting has shown a linear dependence on the concentration of comonomers within the range of feed molarity from 3.5 x 10-1 to 5.0 x 10-1 mol dm-3. The variation of grafting parameters such as graft yield and graft efficiency has been studied as a function of feed molarity and feed composition. The graft copolymers were characterized by various techniques such as FT-IR, TGA/DTA, XRD, and SEM. Further graft copolymers were evaluated for the physicochemical properties such as swelling behavior in different solvents, moisture absorption behavior, and resistance to chemicals as a function of percent grafting. The mechanism for grafting has been proposed based upon experimental observations.

Beating studies for straw-based pulps showed that its freeness decreases faster than wood pulps. In other words, wheat straw requires considerably lower refining energy than wood-based furnish to reach the same level of freeness, due to higher content of primary fines and thinner fibers at lower cell wall thickness. The effect of fiber fractionation and then separate refining of long fiber fraction on refinability and strength properties of wheat straw soda-AQ pulp are discussed in this paper. Thus, soda-AQ pulp of wheat straw was fractionated, using a modified Bauer Mc-Nett fiber classifier having only a 50 mesh screen, into a longfiber fraction (reject) and a short-fiber fraction (accept) at two different mass split ratios of LFR80 (80:20) and LFR60 (60:40). The refined longfiber fractions were re-mixed with the related unrefined short fiber fraction, and their properties were determined in comparison with the control sample. The air resistance, tensile, and burst indices were improved by the fractionation treatments, especially in the case of LFR80, due to higher applied refining energy, which led to higher fiber to fiber bonding. By fractionation of wheat straw pulp and separate refining of longer fiber fraction, it is possible to increase PFI revolutions or refining energy to develop inter-fiber bonding strength without decreasing the tear index.