مجله تحقیقات علوم چوب و کاغذ ایران
سال سی‌ام شماره 2 (پیاپی 51، تابستان 1394)

In this research the effect of softwood cellulose fibers surface characteristics on mechanical properties of cellulose fibers / polypropylene composite (W.P.C) was studied. The fibers were refined to modify the surface characteristics and reach four different freeness levels (11, 14, 17 and 21 °SR). Then the fibers were mixed with polypropylene using pre-determined levels of 20% fibers and 77% polypropylene and 3% MAPP and samples were made. The results revealed that refining the fibers will change the strength of the composites. Statistical analysis should that the impact of the different freeness levels statistically influenced the strength at 99% confidence level. The highest strength levels were reached using fibers with the freeness level of 14 oSR.

In this study the effect of adhesive types and coated veneer on the physical and mechanical properties of particleboard were studied. Two types of coating, including natural veneer of beech and artificial veneer of High Paper Lamination (HPL, formica) and three types of adhesive composition including (100 % UF), (15% PVA + 85 % UF) and (25% PVA + 75% UF) were used to stick the veneer on particleboard. Physical and mechanical properties of the boards were evaluated according to the EN and ASTM standards. The results of this study showed that increasing PVA resin mixed with UF adhesive, in natural and artificial veneers covering, improved the physical and mechanical properties of the boards. Also, the results indicate that the beech veneer boards are more adhesive than formica. However, formica coated boards compared with beech veneer boards, showed higher bending strength and higher modulus of elasticity. It is evident that the water absorption and thickness swelling values in formica coating boards were less than the beech veneer. Collectively, for production of wooden furniture such as library shelves and cabinets, formica decorative coatings must be used to improve the bending strength. The formica decorative coatings are high in abrasion resistance and stable in humid environment. To stick formica decorative coatings on particleboards, the recommended mix design is 25% PVA and 75% UF resin.

In this paper, poly lactic acid (PLA)/ wheat straw fibers manufactured by twin screw extruder and molding compression have been studied. Wheat straw fibers were treated with trietoxymethel silane for better compatibility between two phases. Physical properties, tensile properties of the composites were analysis. The effect of the wheat straw fibers on the thermal properties of PLA has also been investigated in DSC experiments. The effects of silane treatment on the wheat straw fibers have been analyzed by FTIR. Scanning electron microscopy from samples surface were used for better study of water absorption and thickness swelling. Composites wheat straw fiber were treated shows signification lower water absorption and thickness swelling than composites PLA/ untreated wheat straw fibers. The lower amount of water absorption and thickness swelling occurred in the pure PLA. The existence crack and break occurred in the surface of PLA/ untreated wheat straw fibers composites after immersion in the water indicating higher water absorption and thickness swelling were in these samples. Wheat straw fibers were treated with silane due to better wetting and better linkage in the interfacial surface with PLA matrix showed higher tensile properties then PLA/ untreated wheat straw fiber composites. Differential scanning calorimeter test showed that with addition wheat straw fibers were treated to pure PLA the increased glass transition temperatures. The nucleating effect of wheat straw fibers, special treatment with silane cause to increased in the crystallization temperature composites than pure PLA which a positive effect showed on the degree of crystallization.

This article presents the application of agricultural residues fibers (i.e., corn stalk, reed stalk, and oilseed stalk) in order to evaluate and compare their suitability as reinforcement for thermoplastics as an alternative to wood fibers. The effects of fiber loading and CaCO3 content on the mechanical properties were also studied.Overall trend shows that with addition of agricultural residues fibers, tensile and flexural properties of the composites are significantly enhanced. Oilseed fibers showed superior mechanical properties due to their high aspect ratio and chemical characteristics. The order of increment in the mechanical properties of the composites is oilseed stalk > corn stalk > reed stalk at all fiber loadings. The tensile and Impact properties of the composite significantly decreased with increasing CaCO3 content but flexural modulus increased, due to the reduction of interface bond between the fiber and matrix. It can be concluded from this study that the used agro-waste materials are attractive reinforcements from the standpoint of their mechanical properties.

In this study the possibility of using canola stalks mixed with poplar wood in the manufacture of particleboard was investigated. Weight ratio of canola particle to poplar particles at five levels (98, 93/75, 87/50, 81/25, 77%), the weight ratio of the urea-formaldehyde/melamine formaldehyde resin as a adhesive at five levels (23, 18/75, 12/50, 6/25, 2%) and moisture content of matt at five levels (10, 12, 15, 18, 20%) were selected as production variables. Mechanical properties of boards consist of MOR, MOE and IB was tested. According to the results, with increasing the canola stalks/poplar particle ratio MOR and MOE of the boards decreased, but all of the values obtained from treatments were higher than standard. Interaction effect analysis of variables showed that the increasing the ratio of melamine formaldehyde/urea formaldehyde resin decreased the bending strength, while the increasing the moisture of mat increased MOR and MOE. IB values of all treatments are lower than the standard. According to the results of response surface methodology (RSM) and interaction effect between studied variables on the mechanical properties of the panels, the best situation for producing the panels was selected as: weight ratio of 84/32 for canola/poplar particle, ratio of 6/25 for UF/MF resin and moisture content of 12% for mattress.

Among the forest diseases, fungi are the most important factors that cause irreparable losses to the wood in standing trees and logs. Fungi are the cause of contamination and decay of trees and timbers in forest or in the stock of factories. Decayed woods are one of the biomass resources and a great amount of decayed woods in the forests are not viable. In this study some experiments were conducted in order to investigate the effect of Coriolus versicolor decay on compounds obtained from beech wood (Fagus orientalis L.) pyrolysis and preparation of various and valuable chemicals. Separation and identification of chemical compounds in sound wood and decayed wood of beech was conducted by using pyrolysis method at 500° C and in nitrogen atmosphere. Separation and identification of extracted chemical compounds was carried out using sailylation of these compounds by N, O-bis (trimethylsilyl) trifluoroacetamide and also using Gas Chromatography and Mass Spectrometry method. Totally, 23 compounds were identified in sound beech wood which most of these compounds, in this temperature, are related to 2,6-dimethoxyphenol and 3-hidroxy-4-methoxy benzoic acid; and 31 compounds were detected in decayed beech wood that most of them are related to Cyclononasiloxane octadecamethy and 4-(3,4-Dimethoxybenzylidene)-1-(4-nitrophenyl) and also 17 compounds were detected the same in sound and decayed wood.

This research and aim was using Bamboo and Reed CMP pulp for newsprint production. For this purpose, some chips of bamboo stem in the west of Mazandaran were randomly chosen. Then CMP Pulps were prepared at the yield 85%in 120 minutes(Bamboo) and 31 minutes(Reed), by using cooking conditions of Wood and Paper Industries of Mazandaran 60 gr/m2 newsprint handsheets were prepared from the Bamboo and Reed CMP and Mill(MWPI) CMP pulps, first in a separate and then mixed way with 25,50,75 percents. Then the optical and mechanical properties were measured and compared according by using TAPPI Standard test methods. The results showed that the most strength of the burst, breaking length, tensile, tear strength, yellowness and opacity were in the handsheets obtained from 100% the bamboo CMP pulp and the lowest strength (except brightness) was in Reed CMP pulp. The results also pointed out that the above-mentioned all strengths (except brightness) can be improved by using 25-100% of the bamboo CMP pulp, too. The results also indicated that 25-100% of the bamboo CMP pulp and 25% of the Reed CMP pulp can use for newsprint production.

This study with aim of investigation the effect of Nano SiO2 on the physical, mechanical and morphological properties of hybrid Nano composite from polypropylene-wood flour was done. For this purpose, wood flour at 60% weight ratio with polypropylene in extrusion were mixed and Nano SiO2 with 0, 1, 3 and 5% as variable agent were used. Also 4% of MAPP in all compounds as a coupling agent was used. Then Nano composites were manufactured by using injection molding techniques. Then mechanical tests such as tensile and bending and physical tests such as water absorption and thickness swelling in short time according to the ASTM standard was done on the samples. Also To determine how to dispersion of nanoparticles in polymeric matrix was used of Scanning Electron Microscope (SEM). Results showed that increase of SiO2 Nano particles, has positive effect on the mechanical properties and caused the improve them. With Increase in the amount of SiO2 Nano particles the water absorption in Nano composites were increased, but this process for thickness swelling was decrease.

From a long time ago, researchers in the fields of wood science, dendroclimatology and tree physiology were interested in variation of tree-ring width and vessel features within a tree. However, mutual relationship and interplay between these anatomical features were less studied. In this regard, the main question is whether the pattern of adjustment in wood anatomical traits (tree-ring width and vessel features) is similar in all hardwoods and in every site? Or may the same species chose different strategies in different sites? To answer these questions, two growing sites of black alder (Alnus glutinosa) with completely different micro-climates (dry and brackish) were selected near Astara city. In each site, a few trees were selected, cut or cored. After preliminary treatments, wood cross sections were prepared from the bark to the pith of each tree. These sections were scanned and by using an image analysis software, tree-ring width (TRW), average vessel lumen area (AVLA), number of vessel in the unite of an area (VF), and the porosity (Porosity) of a tree ring were measured in the last 20 annual rings of each tree. To study the inter-relations between variables at each site, they were analyzed using different statistical tests. The results showed that the inter- and mutual-relations between tree-ring width and vessel features were similar in tow studied sites. In brief, it can be concluded that regardless of site and climatic condition, in alder trees, wider tree rings leads to fewer vessels and these two anatomical traits are controlled by the same component but AVLA is affected by a different component and is not associated with the tree-ring width.

In this research, the effect of vine pruning fibers in combination with wood fibers on contact angel (wettability) and surface bond strength of medium density fiberboard was studied. One layer laboratory panels with a thickness of 15 mm and density of 650 Kg/Cm3 were produced. Variable factors were vine pruning fibers content in three levels of 0/100, 30/70 and 60/40 by weight and press time in three levels of 4, 5 and 6 minutes. The wet ability and surface bond strength of panels were measured. Results showed that the contact angle of the boards was reduced when the vine pruning fibers content increased up to 60%. Press time had significant influence on wet ability of test panels. So that the contact angle was increased with increasing the press time up to 5 minutes. Whereas the contact angle was reduced when the press time of panels increased to 6 minutes. In addition, the results indicated that the sanding of panels caused a decrease of contact angle in the boards. Moreover the surface bond strength of panels were reduced with adding vine pruning fibers up to 30% whereas the panels produced using 60% vine pruning fibers showed stronger.

Cellulose is one of the most abundant natural biopolymer on earth is renewable, biodegradable and non-toxic. Micro and Nano-scale cellulose fibers and their applications in composite materials due to their high strength and stiffness combined with low weight, biodegradability and renewability has attracted considerable attention. In this study, Micro-crystalline cellulose (MCC) of the skin of the cotton plant by acid hydrolysis in 2N hydrochloric acid to acid ratio of dough the Nano-crystalline (NCC) were prepared by chemical methods. Effect of hydrolysis conditions on properties such as the crystallinity and crystal size Micro and Nanocrystals cellulose with measurement range into the infra-red February (FT-IR), X-ray diffraction (XRD) were reviewed and The shape and size of the samples by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were studied. Fiber analysis using x-ray showed that increasing the amount of acid in the crystallinity of cotton cellulose Micro- crystalline increase the crystal size does not change Lower moisture uptake. Cotton cellulose Nanocrystals and crystal size greater than Micro- crystalline size were reported.

This study was conducted to evaluate stress carrying capacity of miter corner joints fabricated with loose tenon with loose tenon under diagonal tension and compression loading. In this study, tests were carried out to determine the effects of dimension of loose tenon A (3.5 × 1 × 0.8 cm) and B (3 × 2 × 0.8 cm), type of adhesives (Polyvinyl acetate (PVA) and polyurethane (PU)) and most commonly used wood species in furniture industry including beech (Fagus orientalis L.) and fir (Abies alba). The results indicate the stress carrying capacity joints under compression is higher compared with that in tension. Stress carrying capacity joints constructed with dimension of loose tenon A was higher than that of those with B. Furthermore, the results have shown that wood species and type of adhesive had significant effect on the stress carrying capacity and performance of joints constructed of Beech wood and PU adhesive were stronger than joints made of Fir wood and PVA adhesive.

In this study, production of bleached chemical- mechanical pulp from wheat straw for newsprint papermaking was investigated. Wheat straw for pulping was obtained from Lorestan province. Wheat straw CMP pulp was prepared at 120, 140, and 160 °C temperature, 45 minute time, 10, 12, and 14% chemicals charge and 10:1 cooking liquor and straw ratio. The yield after defibration treatment varied between 56.5% and 72.5%. Two optimum pulps bleached by TCF method applying 2% and 3% NaOH, 1.5% and 2% H2O2, and 60 and 120 minutes bleaching time. One way analysis variance method showed that bleaching time had the most significant effect on optical properties of handsheet. Applying 3% (based on oven dry weight of the unbleached pulp) NaOH, 2% H2O2, and 120 min. in bleaching improved the brightness and opacity to 52.9%, and 79.5% ISO, respectively. Optimum pulp strengths including tensile, burst and tear indices were measured 43.87 Nm/g, 2.18 kPa.m2/g, and 8.46 mN.m2/g, respectively. All the strengths were higher than newsprint paper strength produced by Mazandaran wood and paper and Korean companies.

In this research the mechanical and barrier properties of hand-sheets made of virgin and recycled fibers were studied after coating by chitosan and poly (vinyl alcohol) polymer blends. Therefore to evaluate coatings effects on barrier properties, water vapor transmission rate (WVTR), water absorbance, air resistance and grease proof of coated papers were determined. Moreover, mechanical strength including tensile strength and burst strength were measured. According to the results, the barrier properties and mechanical strength of coated papers improved dramatically than uncoated ones. The best results in WVTR and mechanical strength tests were obtained for coatings with the same ratio of polymers. On the other hand, coating with 75%chitosan - 25% poly (vinyl alcohol) composition exhibited excellent resistance against the grease penetration and water absorption.

The aim of present study was to determine the relationship between ultrasonic wave velocity and mechanical properties of particleboard panels. For this purpose, homogenous and layering particleboards were made by 0/7 g/cm3 density and 16 mm thickness. After conditioning and preparing samples, ultrasonic wave velocity was measured in different directions of samples. Then modulus of elasticity, modulus of rupture and internal bonding of samples were measured by mechanical test machine. Result indicated that ultrasonic wave velocity of particleboard samples was higher in longitudinal direction than other directions. Relationship between ultrasonic wave velocity and mechanical properties was determined by linear correlation regression. Correlations between ultrasonic wave velocity and modulus of elasticity, modulus of rupture and internal bonding were significant in thickness direction of particleboard samples. Correlations between ultrasonic wave velocity and modulus of elasticity, modulus of rupture and internal bonding were significant in thickness direction of particleboard samples. Correlations between ultrasonic wave velocity and modulus of elasticity, modulus of rupture and internal bonding were significant in thickness direction of particleboard samples.