مجله صنایع چوب و کاغذ ایران
سال چهاردهم شماره 4 (زمستان 1402)

In this research, the shear strength of joints made of medium-density fiberboard (MDF) and particleboard with screwshas been evaluated. Therefore, T-shaped joints were made from two pieces with a dimensions of 7.5 x 15 cm by one screw as a fastener. The screw was selected as a variable in three levels of diameter: 4.2, 5 (panel screw), and 6 mm (Allen socket head cap screw). The Joints, were tested under shear load in two directions, parallel and perpendicular to the edge of the main member. The loading rate was 5 mm/min. The results have shown that MDF and particleboard have similar performance against shear loading. The screw diameter had a significant effect on the strength of joints in shear loading. Joints made with MDF and particleboard have a better performance against shear load when the load was perpendicular to the edge of the main member. Also, the results have shown that the joints made with 6 mm diameter screws in both MDF and particleboard show more resistance against shear loading. This increase was more noticeable in the case of loading perpendicular to the edge of the main member. The mode of failure results showed that the loading type affected in the failure of specimens. In parallel loading to edge loading internal bounding has been effective, while in perpendicular to edge loading in addition to the internal bounding, surface density has also been effective.

In this research, the influence of MDF sawdust with coal sawdust additives, sulfur and recycled rubber powder on the physical and mechanical properties of wood plastic composite was investigated. Recycled rubber powder was used at 3 three levels of 0, 2.5, and 5 wt% and sulfur at three levels of 0, 2 and 4 wt% as well as coal sawdust and MDF with ratios of 30 and 60%. The materials inside the torque mixer machine were mixed and after taking out and cooling the materials were converted into granules with a semi-industrial crushing machine, and the granules were poured into the mold and placed under a hot press, and finally a cold press was used. Mechanical properties including bending, tensile and compressive strength, bending and tensile modulus, as well as physical properties including water absorption, thickness swelling at 2 and 24 hours were measured. The results showed that the addition of 60% MDF sawdust increased the strength and modulus, and with the increase of rubber powder and sulfur, the strength and modulus decreased. Water absorption and thickness swelling of 2 and 24 hours decreased with the addition of 60% coal sawdust, 4 wt% sulfur and 5 wt% recycled rubber powder. The results of bending, tensile and compressive strength were confirmed by Scanning electron microscopv.

In this study, the effect of nano-copper particles on heat transfer in the cycle, press and mechanical properties of boards of five layers was studied .Two species Iranian beech and Populus deltoides and nano-copper particles at four levels of (0, 5, 10 and 15%) of the time, Press (4, 5 and 6 minutes) as the variable factors were considered in this study. Mechanical strength of plywood (including MOR and MOE, SH) were measured.Results indicate that mechanical strength of plywood (including MOR and MOE, SH) after a primary increase from 4 to 5 minutes of press time decreased after 6 minutes of press time. Increasing intake soluble nano copper from 0 to 10% and cause an improved the in MOR and MOE . So it can be attributed to reason increasing speed of heat transfer and glue absorption cause an improved the boards. But with increasing consumption 15% reduction in the features.In all the the mechanical strength of boards, Species of beech very good performance compared to Populus deltoids that so it can be attributed to internal bond improvement.

In this study, the effect of changes in pH and molar ratio on the properties of melamine formaldehyde resin for impregnating decorative paper was investigated. The physical properties of the resin such as free formaldehyde, resin shelf life, and the percentage of resin solids contents were investigated in different conditions Also, the molecular structures of resin were studied using FTIR spectroscopy and thermal analysis of resins through TGA. The results showed that a higher pH improved the characteristics of the resin and melamine coating, while increasing the molar ratio of formaldehyde to melamine weakened the characteristics of the resin and coating. In addition, the results showed that the changes observed in the resin caused by The variables of molar ratio and pH have no significant effect on the thermal properties of the resin.

Recognition of the natural durability of wood and industrial species of each country is essential and Iran is no exception to this rule because of valuable commercial species. Generally, the natural durability of wood is determined in the laboratory and field by measuring the decay resistance of wood according to EN 113 and EN 252. However, Meyer- Veltrup et al. proposed a new method entitled "resistance model" to estimate the natural durability with more accuracy which can be generalized to conditions without soil contact. In this model, two factors namely inherent resistance and wetting ability are used. Beech (Fagus orientalis) was selected as one of the most important commercial species in Hyrcanian forests to study its natural durability. The results showed F. orientalis heartwood and sapwood were less durable and non-durable (DC 4–5). Water immersion after 1 and 24 hours was highest for sapwood followed by heartwood. Based on the MLF index, 61 % of sapwood was attributed to the white fungus (T. versicolor) as well and the lowest MLF was caused by sapwood and heartwood by the H. Fragiforme. 43.5 % of MLF on beech wood is caused by terrestrial organisms (TMC). Based on the resistance model, the first signs of decay were observed after 312 and 294 days.

The use of engineered wood products in the construction industry is constantly increasing due to various technical and economic reasons such as high strength-to-weight ratio, lack of restrictions in access to different dimensions, and the possibility of production using waste. I-shaped beams are one of the types of engineered wood products which Their properties can be controlled according to the design and the type of materials used in it.This study is done For the purpose of investigate the Reinforcement of I-shaped beams made with parallel strand lumber and laminated veneer lumber reinforced with glass fibers and epoxy resin. The variable factors of this research included the type of web and flange. The mechanical properties of the manufactured beams, including bending strength, modulus of elasticity, shear strength of the web, compressive strength parallel to the flange and compressive strength propertional limit of the flange were investigated and tested. The obtained results were analyzed in the form of a completely random design and Duncan's test was used to group the means. The results showed that the use of laminated lumber reinforced with glass fiber polymer in the web of beam compared with conventional laminated lumber Cause of improvement the modulus of rupture by 49.6%, the modulus of elasticity by 73.17%, the shear strength of the web by 55.55%, compressive strength parallel to the flange by 16/41% and 20.65% of the compressive strength propertional limit of the flange. Also, the use of laminated lumber reinforced with glass fiber polymer in the flanges of beams had a much better mechanical performance than conventional laminated lumber, parallel strand lumber and parallel strand lumber reinforced with glass fiber polymer.

Foams made from poly-lactic acid, which is a natural polymer, have been introduced as an alternative to petroleum-based foams. However, the use of these foams faces limitations in terms of physical and mechanical characteristics. To improve the quality of poly-lactic acid foams, natural nucleating agents such as cellulose derivatives can be used. The effect of micro-crystalline cellulose as a nucleating agent in the production of poly-lactic acid/wood flour foam with azodicarbonamide foaming agent was investigated. The results revealed that by increasing the foaming agent content up to 3% and the nucleating agent content up to 4%, the density of the foam panels decreased by 45.52%. The reduction in density was accompanied by an increase in porosity, expansion rate, water absorption, and thickness swelling throughout all treatment levels (1 to 3% foaming agent and 1 to 4% nucleating agent), and this decrease in density led to a reduction in tensile and flexural strength and an increase in impact resistance. The morphological changes of the produced foams were also confirmed by scanning electron microscopy (SEM) images.

The increase in industrial activities has increased the demand for energy sources. The use of existing energy sources (mainly fossil fuels) causes a lot of damage to the environment. Therefore, it is necessary to find a suitable alternative for fossil fuels. One of the suitable alternative sources for fossil fuels is lignocellulosic biomass. In this regard, it is necessary to make changes in raw biomass by using appropriate methods and prepare them for energy supply purposes. One of these methods is converting biomass raw materials into fuel briquettes. In this research, the effect of using almond shell flour and recycled old cardboard in the production of fuel briquettes was investigated. The results of this research showed that treatment A2 (100% recycled old cardboard) had the highest amount of density, compressive strength and ash (1.319 g/cm, 178.94 N/mm and 18.4%, respectively). Treatment A1 (100% almond peel flour) had the highest amount of volatile substances and fuel stability rate (79.48% and 3.67 g/min, respectively). In the control sample (100% wood flour), the highest calorific value (20.53 MJ/kg) was observed.

In this research, the strengthening of wheat straw cold soda pulp produced in Iran using tomato stalk fibers prepared by soda-anthraquinone process was investigated. Length, diameter, cell cavity diameter, and fiber thickness; Runkle ratio, slenderness ratio and flexibility coefficient of tomato stalk fibers were measured. The chemical composition of tomato stalk including percentage of ash, lignin, cellulose and hemicelluloses were determined. Unbleached pulp was produced from tomato stalk in 180 minutes with optimal conditions of 170°C, 20% active alkali and 0.1% anthraquinone. The average yield percentage after screening and kappa number of tomato stalk pulp were measured as 43.09 % and 27.33, respectively. Hand sheets made from this pulp has the tensile index of 34.75 (Nm/g), tear index of 6.02 (mNm2/g) and burst index of 2.16 (kPam2/g), respectively. The combination of tomato stalk pulp with wheat straw cold soda pulp available in the market was done at three levels: 75:25, 50:50 and 25:75. The amount of tensile, tear and burst indices increased by 28, 63 and 36 % respectively after mixing. The most obvious effect of mixing in terms of mechanical properties is observed in the increase of tear index. The results show that the addition of unbleached soda-anthraquinone tomato stalk pulp as an unused agricultural waste to the unbleached wheat straw cold soda pulp can improve and increase the mechanical indices by reducing the weaknesses of the cold soda pulp and also leads to expanding the application and demand for this pulp.