مجله تحقیقات علوم چوب و کاغذ ایران
سال بیست و هشتم شماره 4 (پیاپی 45، زمستان 1392)

In this study, feasibility of foaming wood plastic composites using injection molding process was investigated. The effect of lignocellulosic raw material (Poplar saw dust and soybean straw flour) on the properties of composites was examined. Wood plastic composite boards with 3.2 mm thickness, 105 mm width and 105 mm length were prepared using high density polyethylene granules. The foaming agent (Azodicarbonamide) at 2 wt % was also used. The scanning electron microscope micrographs confirmed that foaming process has been successfully carried out. The Results showed that all mechanical properties (except the impact strength) decreased while water absorption increased as the microcellular foaming method was used. Adding soybean straw flour to the foam structure led to the decrease in flexural strength, flexural modulus of elasticity and tensile strength. Water absorption and thickness swelling were negatively affected with the addition of soybean straw flour.

The purpose of this study was to examine the physical and mechanical properties of particleboard made using corn stalk. Mixtures of corn stalks and industrial wood particles at the ratios of 0:100, 30:70, 50:50, 70:30, urea-melamine formaldehyde resin at two levels of 10 and 12% (based on the dry weight of the particles) and two press times of 5 and 6 minutes were used for the production of laboratory particleboard. Physical and mechanical properties including water absorption and thickness swelling after 24 hours soaking in water, modulus of rupture, modulus of elasticity and internal bonding were measured and the data were statistically analyzed. It was observed that the increase in corn stalk particles in the mixture resulted in reduction of water absorption, thickness swelling after 24- hours water soaking and the internal bonding. The modulus of rupture and elasticity of the boards were increased at higher ration of corn stalk particles. The higher dosage of resin and higher press time imposed significant effect on all properties boards and improving properties were reached. In general, comparing the produced boards properties with EN 312 requirements, the boards produced using 70% corn stalk particles, 12% urea-melamine formaldehyde and 6 minutes press time showed optimal properties.

In this study, physical and mechanical properties of wood-plastic composite made of Canola stem flour and polypropylene were investigated. Variable factors were four levels of canola stem flour (25, 50, 75 and 100 percent based on the dry weight of the wood flour) with and without pit. The control samples were made of only wood flour and polypropylene. Physical and mechanical properties including screw withdrawal strength perpendicular on the surface, flexural strength, modulus of elasticity, water absorption and thickness swelling after 2 and 24 hours immersion in water were measured in accordance with EN standards. Results showed that increasing the mixing ratio of canola stem flour to wood flour up to 25% resulted in increase in screw withdrawal strength perpendicular to the surface. Increasing this factor up to 50% led to increase in MOR and MOE. Thereafter, any increase in the mixture, decreased mechanical strengths. Increasing the mixing ratio of canola stem flour to wood flour resulted in increase in water absorption and thickness swelling after 2 and 24 hrs. The specimens without pit showed lowest amount of water absorption and thickness swelling levels and highest mechanical properties (screw withdrawal resistance, flexural strength and modulus of elasticity).

Paper industry has been experiencing growing shortage of cellulosic material over the last decades. As a fast-growing plant, kenaf has good potential to compensate wood shortages taking into account its long historical record of cultivation in Iran. Kenaf variety of 432 was collected from Varamin research station. Kenaf stalk yield was determined roughly as 10.5 air-dried metric tonnes (ADMT) per hectare for a single crop rotation. Soda pulping of core, bast and their mixture were carried out at three weight percent ratios of 50:50, 40:60 and 30:70. H-factor for the delignification process was adjusted about 800 using cooking treatment combination of 175 °C, 30 min, 18% sodium hydroxide, and 5:1 liquor to raw material ratio. Under similar cooking condition, yield and kappa no. of soda pulp prepared from the mixture of kenaf core and bast showed highest yield and kappa number. Kappa no. decreased with increasing bast fiber percent from 50% to 70%, and required increased PFI revolution to achieve certain freeness. Handsheet properties including thickness, breaking length, burst and specially tear index increased at higher bast fiber content.

In this research, the effect of nanoclay-particles on physical and mechanical properties of composites made using almond shell powder-polypropylene was studied. For this purpose, almond shell powder and nanoclay were used in three levels of 30%, 35% and 40% for almond and 0%, 2.5% and 5% for nanoclay. In addition, 2% of Maleic Anhydride Polypropylene was added to all compositions. Then, wood-plastic nano-composite was formed using counter-rotating twin screw extruder and injection molding machine. Mechanical test including tensile, flexural, impact resistance, hardness and physical properties including water Absorption and Thickness Swelling after 2h and 24h immersion in water were measured. In addition X-Ray Diffraction (XRD) experiment was carried out to reveal how clay nano-particles are distributed across the manufactured composites and Scanning Electron Microscope (SEM) was also performed to investigate fracture surfaces. The results indicated that the presence of nano-clay did not influence the flexural and tensile elasticity modulus, and the presence of nano-clay reduced tensile and flexural resistance. The hardness and density of composites were higher than pure plastic and the impact resistance of all composites was lower than pure plastic. The presence of nano-clay did not significantly effect the physical properties of the composites (p< 0.05).The diffraction model of X-ray showed that nano-composite forms intercalation interlayer structure and the results of morphological investigation revealed that the samples containing 2.5 percent nano-clay and 35 percent of almond shell have the highest array of intercalation and the best transmittance.

The objective of this study was to examine the effect of Paulownia particles addition and pressing time on the surface quality of particleboard made. In this regard, Paulownia chips and industrial chips were used in surface and core layers, respectively. Urea-formaldehyde resin was applied at 12% for surface layer and 8% for core layer. Variables include Paulownia chips charges at 3 levels of 10, 20 and 30 percent and 2 pressing time (6 and 8 minutes). To evaluate surface roughness of the samples a completely randomized design was used and 8 roughness parameters include average roughness (Ra), maximum roughness (Rmax), average bumps and troughs (Rz), maximum vale depth under the average (Rv), maximum peak on the average line (Rp), Abbott group parameters included Rk, Rpk, Rvk, were measured according to ISO4287 standard using roughness measuring device available in Grogan university of agricultural sciences and natural resources. Surface quality of the particleboard improved as the pressing time (6 to 8 minutes) and the Paulownia chips charges (10 to 30 percent) increased.

In this study, pulp and handsheets characteristics of radiata pine wood kraft pulp was evaluated. The ratiata pine wood was collected from Chamestan Noor Research Station. Average dry and basic specific gravity of wood were determined as 0.342 and 0.308 g/cm3 and average fiber (tracheid) dimension including fiber length, fiber diameter, lumen diameter and cell wall thickness were measured as 2460, 40.35, 33.17 and 3.59 µm, respectively. The chemical composition was determined as holocellulose 72.07%, alfa cellulose 43.41%, lignin 29.95%, ash 0.50 % and extractive as 1.75%. Kraft (Sulfate) process was applied for cooking and pulping the wood. A factorial randomized complete block design test was conducted to compare the fiber dimensions, physical properties, chemical composition and the yield of the pulp. To examine strength properties of handsheets, ANOVA statistical analysis was used and for grouping the means Duncan test were applied. The minimum and maximum yield and kappa number of these pulps were measured at 40.33%, 50.43% and 33.89, 60.22, respectively. The results of handsheet strength measurement indicated that radiata pine wood kraft pulp provides suitable substitute for imported long fiber pulp to be mixed with short fiber hardwood pulp.

To compete in value creating and attempt to achieve sustainable competitive advantage and a strategic advantage over competitors have resulted in an increased attention to the importance of customer and his/her satisfaction. This is particularly important in extensive furniture and wood industry that deals with a wide range of customers with different tastes and attitudes. As a result, this study using library research and customer survey, attempts to identify factors influencing customer satisfaction and determine their relative impact using TOPSIS as one of the most important multi-criteria decision-making methods. The results indicate that the developed conceptual model consists of six major indexes—beauty and appearance, quality, competitive pricing, distribution and delivery systems, after-sale and support services and 35 sub-indexes. Ranking the sub-indexes reveal that the sub-indexes: fitting to indoor space; fabric, foam, and wood parts quality; product durability according to purchase price; on-time delivery; sales person’s honesty and responsiveness to provide technical knowledge; and the superiority of the household wood furniture in comparison to other similar products are the most important factors that affect customer satisfaction. On the other hand, Sub-indexes of size and volume, maintainability, purchase facilities provided by the company, method of installation, availability of product specification manual, and the environmental factors are found to have the least impact on customer satisfaction.

Ephedra shrubs are among native species of Iran and Turan habitat but their anatomical and physical characteristics have not been studied yet. In this study,physical characteristics of wood logs from three ephedra species including Mianeh Ephedra (Ephedra intermedia),Goats Beard Ephedra (Ephedra major) and Deserts Ephedra or Central Asian Ephedra (Ephedra strobilaceae Bge.) from desert areas of Yazd province were studied. Results shows that Iranian ephedra species similar to the others species show three key anatomical structures: Vessles, Theracheids and, Fibers. The presence of big pits simillar to tracheid pits in some vessel elements support the idea that they are a bridge group linking angiosperms and gymnosperms. Important anatomical features of Iranian ephedras include occurrence of clear and dendroied bodies, elongated and very hetrogenous wooden rayes and latticed vascular valves. Anatomical differences between the three ephedra species provide the key to identify them. There was not any significant difference between average physical characteristics (wet and dry density, shirinkage and swelling).Whereas, average shirinkage and swelling in radial direction was significantly higher than those in tangentiels direction.

Increasing demand for light and durable materials in home and office furniture requires optimizing the properties of the products used. In this research the effect of skin type and core on mechanical properties of light weight sandwich panel was investigated. The skins were made of MDF with 3, 6 and 8 mm thickness, particle board with 8 mm thickness, three layer plywood with 3.8 mm thickness and five layers plywood with 7.28mm thickness. The cores of polyurethane foam and honeycomb of kraft paper (3 cm thickness) were used. Mechanical tests including bending strength, modulus of elasticity; impact bending and compression were performed according to DIN and ASTM standards. Result showed that, light sandwich panels made from polyurethane foam core had higher mechanical properties than the light panel made of kraft honeycomb core which indicates that the dense and homogenous structure and better linkage with skin. By increasing the thickness of skin in the samples made from MDF skin, the properties of sandwich panel increased. The best result of mechanical properties was observed in light weight sandwich panel made of plywood skin and polyurethane core.

Dissolution and Cellulose-Nylon composites preparation in liquid phase was studied. BMIMCl ionic liquid was synthesized in the laboratory and was used to perform the dissolution purpose. After the dissolution of the polymers, Cellulose and Cellulose-Nylon composite films were prepared and processed. Then the transparency, water absorption and thickness swelling, water vapor permeability and tensile strength of the composite were determined. Further characterization was performed using SEM and FTIR techniques. Results showed that both polymers were compatibly dissolved in Ionic liquid and homogenously blended which indicates chemical bonding was established between the polymers. Transparency, water absorption and thickness swelling decreased and water vapor permeability of the composites increased compared to pure cellulosic film. Also, mechanical strength, Young's modulus and strain at break point of the composite were decreased compared to reference cellulosic film.

In this study, the possibility of using canola tree stem residues and nanoclay particles on physical, mechanical and morphological properties of canola wood flour – polypropylene composites was investigated. The weight ratio of canola wood flour and polypropylene in the mixture was 50% and 50%and 0, 3 and 5 percent nanoclay and 4% MAPP were used. First, the ingredients were mixed using the extruder and then final panels were produced by hot pressing the compoud. Physical and mechanical properties were measured. Results indicated that water absorption and thickness swelling of the composites decreased as the nanoclay content was increased. The screw and nail withdrawal strength of wood plastic composite increased with increasing nanoclay up to 3% percent, then decreases with the increasing nanoclay to 5%. Morphologies of the nanocomposites were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the results showed increased d-spacing of clay layers indicating enhanced compatibility between polypropylene and nanoclay and canola stalk flour.

Sweet locust and False Acacia are important species of northern forests region with wood having good durability. In this study, three disks from each species were randomly cut in Nowshahr forest region. For homogenous sampling, first wood flour was prepared from each disk according to TAPPI standards and then mixed together. Acetone was used to remove extractives from both Sweet locust and False acacia wood flour. Extracts were analyzed by GC/MS. For the identification of compounds, GC diagram which shows abundance and retention time of each compound and calculation of quartz index and Adams table were used. The results showed that there are almost 150 compounds in False Acacia wood, and among them Resorcinol(19.47%),1,3-Benzendiol(6.92%), Stigma sterol (5.45%), 9-Octadecenoic acid(3.55%),1H-Imidazol(3.08%),Gamma-sitosterol (2.77%) and Gamma-Terpinene(0.22%) were the predominant compounds. There are 37 compounds in Sweet locust wood, that 1,2-Benzenedicarboxylic acid (90.38%),Stigmast-4-en-3-one(2.62%),Resorcinol(1.07%),Silicon grease (0.73%), Gibberellins A3(0.14%) and Phenol(0.09%) were important compounds. Resorcinol and 1, 2-Benzenedicarboxylic acid occurs both in Sweet locust and False acacia woods. The presence of high percentage of Resorcinol (20%) in Sweet locust and 1,2-Benzenedicarboxylic acid (90.38%) in False acacia are attributed for the durability of these species.

This research was conducted to determine the physical properties of poplar wood treated with silica colloidal nanoparticles prepared from rice husk using ash making and alkaline digestion. Test samples were prepared according to ASTM-D1037 standard with the dimension of 2×2×2 cm and then were impregnated ina cylinder according to Bethell method applying five concentration levels of soluble colloidal silica nanoparticles (0, 1.2, 1.7, 2.2 and 3.2%). Nanoparticle retention and absorption, density changes, water absorption, and anti-swelling efficiency (ASE) were determined. Nano silica absorption was determined as 119.8, 169.5, 196.3 and 214.7 % corresponding to 1.2, 1.7, 2.2 and 3.2 % nanoparticle addition, respectively. Nano-silica retention in the lowest and the highest treatment level were 1.2 and 9.3%. Results showed that the density increased from 0.37g/cm³ in control samples to 0.40 g/cm³ at the highest level of nano-silica absorption. Water absorption increased by increasing nano-silica absorption. However, dimensional stability of impregnated samples increased. After the longest immersion time, average swelling volume of the sample impregnated with nano-silica was decreased in comparison with the control sample. With increasing nano-silica absorption, anti-swelling efficiency of impregnated samples treated at the 1.2, 1.7, 2.2 and 3.2 % level and immersed for 168h was 36.5, 42.9, 34.7 and 26.8 %, respectively.

Technology, Gorgan University of Agricultural Sciences and Natural Resources, Iran., The purpose of this study was to compare the properties of wheat straw (Zagros sp) collected in Golestan province NSSC pulp under alkaline pretreatment with 1% sodium hydroxide and boiling pretreatment. Wheat Straw pretreatment with 1% sodium hydroxide and hot water at water to straw ration of 10 to 1 was conducted at 70ْC for half an hour. NSSC pulping was carried out at constant pulping condition including liquor to straw ratio of 5:1, maximum temperature at 160ºC for 30 minutes. In order to study the effect of sodium hydroxide on strength properties of paper in some cases only Na2S03 was used. After pulping, defibration was carried out by laboratory refiner to reach 380±25ml (CSF). Sixty gram/m² hand sheets were prepared from each pulp. The strength properties were determined according to TAPPI standard. Results showed that with the exception of RCT strength, pretreatment had significant effect on increasing the strength properties of papers and by alkaline pretreatment, brightness of the pulps decreased and tensile strength, burst strength, breaking length, stiffness and density increased. Using chemical pretreatment especially sodium hydroxide resulted in reduction in yield and brightness level and improvement in strength of the pulps.