Iranian Journal of Wood and Paper Science Research
Year:2015 | Volume:30 | Issue:2|Papers Count:17

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

In this study, the effect of adhesive types and veneer laminating on the physical and mechanical properties of particleboard was studied. Two types of veneer laminates, including beech natural veneer and artificial veneer (High Paper Laminates, HPL, called formica) and three mixtures of adhesives including (100% UF), (15% PVA+85% UF) and (25% PVA+75% UF) were used to adhere the veneer laminates on particleboard. Physical and mechanical properties of the laminated boards were evaluated according to the EN and ASTM standards. The results of this study showed that increasing PVA resin in the mixture with UF adhesive to glue both natural and artificial veneers improved the physical and mechanical properties of the boards. Also, the results indicated that the bond strength of beech veneer on boards was stronger than formica. However, formica covered boards as compared with beech veneer covered boards showed higher bending strength and higher modulus of elasticity. It is evident that the water absorption and thickness swelling values in formica laminated boards were less than the beech veneer. Therefore, for the production of wooden furniture such as library shelves and cabinets, formica must be used to improve the bending strength. The formica decorative covering are more abrasion resistance and resistant in humid environment. To glue the formica decorative veneer on particleboards, the recommended adhesive mixture should be 25% PVA and 75% UF resin.

In this paper, the properties of polylactic acid (PLA) / wheat straw fiber composites manufactured using twin screw extruder and compression molding were studied. Wheat straw fibers were treated with trietoxymethel silane to produce better compatibility between two phases. Physical and tensile properties of the composites were measured and analyzed. The effect of the wheat straw fibers on the thermal properties of composites was determined using DSC techniques. The effect of silane treatment on the wheat straw fibers was analyzed by FTIR. Scanning electron microscopy of composite samples surface were used to study water absorption and thickness swelling. Composites made using treated wheat straw fiber showed significantly lower water absorption and thickness swelling than composites made using PLA/ untreated wheat straw fibers. The lower amount of water absorption and thickness swelling occurred in the pure PLA composites. The cracks and break occurred at the surface of PLA/ untreated wheat straw fibers composites after immersion in the water indicating higher water absorption and thickness swelling. The treated wheat straw fibers due to better wetting and better bonding at the interfacial layer with PLA matrix showed higher tensile properties compared with PLA/ untreated wheat straw fiber composites. Differential scanning calorimeter test showed that with the addition treated wheat straw fibers to PLA increased glass transition temperature. The nucleating effect of wheat straw fibers, special treatment with silane increased in the crystallization temperature of composites compared to PLA which is a positive effect on the degree of crystallization.

This article presents the potential of the application of agricultural residue fibers (i.e., corn stalk, reed stalk, and oilseed stalk) in the production of composites and compares their suitability as reinforcement for thermoplastics as an alternative to wood fibers. The effects of fiber loading and CaCO3 content on the mechanical properties of the composites were also studied. Overall trend showed that with the addition of agricultural residue 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 improvement 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 interfacial bond between the fiber and matrix. It can be concluded that agro-waste materials are attractive reinforcements from the standpoint of 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 to poplar particles was selected at five levels (98; 2, 93.75: 6.25, 87.50: 12.50, 81.25: 18.75, 77: 23), the weight ratio of the melamine-formaldehyde/urea formaldehyde resin as adhesive was adjusted at five levels (23: 77, 18.75: 81.25, 12.50: 87.50, 6.25: 93.75, 2: 98) and moisture content of the mat at five levels (10, 12, 15, 18, 20%) were selected as production variables. Mechanical properties of boards including MOR, MOE and IB were measured. According to the results, at higher canola stalks/poplar particle ratio, MOR and MOE of the boards decreased, but all of the values measured from the treatments were higher than standard. The results showed that increasing the ratio of melamine formaldehyde/urea formaldehyde resin decreased the bending strength, while the increasing the mat moisture increased MOR and MOE. IB values of all treatments were lower than the standard. According to the results of response surface methodology (RSM) and the effect of studied variables on the mechanical properties of the panels, the best condition for producing the panels was selected as: weight ratio of 84.32: 15.68 for canola/poplar particle, MF/UF resin ratio of 6.25: 93.75 and the mat moisture content of 12%.

Among the forest diseases, fungi are the most important that causes extensive deterioration to the wood in standing tree and logs. Fungi cause contamination and decays trees and timbers in forest as well as in the mill yards. Decayed woods are the source of biomass and a great amount of decayed wood is present at the forests as un-used material. In this study, experiments were conducted to investigate the effect of Coriolus versicolor decay on chemical compounds obtained from beech wood (Fagus orientalis L.) pyrolysis. Separation and identification of chemical compounds in beach sound wood and decayed wood was conducted using pyrolysis at 500oC 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 Gas Chromatography and Mass Spectrometry. Totally, 23 compounds were identified in sound beech wood and most of these compounds, at this temperature, are related to 2, 6-dimethoxyphenol and 3-hidroxy-4-methoxy benzoic acid; and 31 compounds were detected in decayed beech wood which most of them are related to Cyclononasiloxane octadecamethy and 4- (3, 4-Dimethoxybenzylidene) -1- (4-nitrophenyl) and17 compounds were detected in both sound and decayed wood.

The objective of this research was using Bamboo and Reed CMP pulp for newsprint production. For this purpose, some bamboo stem chips were randomly selected from west of Mazandaran. Then CMP pulps were prepared at the yield 85% applying 120 minute pulping time for Bamboo and 31 minutes for Reed, using cooking conditions of Mazandaran Wood and Paper Industries. The 60 gr/m2 handsheets were prepared using bamboo and reed CMP pulps and mill (MWPI) CMP pulp as control and also with mixtures of 25, 50, 75% mill pulp combined with either bamboo or reed CMP pulp. Then the optical and mechanical properties of the handsheets were measured as defined in TAPPI Standard test methods. The results showed that the handsheets obtained from 100% the bamboo CMP pulp showed the highest burst, breaking length, tensile, tear strength, yellowness and opacity and the lowest strength (except brightness) was related to reed CMP pulp. The results also revealed that the above mentioned strength (except brightness) can be improved using any combination of bamboo CMP pulp with mill pulp. However, if it is intended to use reed CMP, then 25% of the reed CMP pulp can be used for newsprint production.

The objective of this study was to investigate the effect of Nano SiO2 on the physical, mechanical and morphological properties of hybrid polypropylene-wood flour nano-composite. For this purpose, 60 parts wood flour, 40 parts polypropylene and 4 parts MAPP was used. Nano SiO2 at 0, 1, 3 and 5% was added to this mixture as variable factor. Then the materials were compounded in an extruder and nano-composite samples were manufactured using injection molding techniques. Mechanical strength of the samples including tensile and bending and physical properties such as water absorption and thickness swelling in short time were determined according to the ASTM standard. Also the dispersion of nanoparticles in polymeric matrix was evaluated by Scanning Electron Microscopy (SEM). Results showed that at higher dosage of SiO2 nano particles, mechanical properties were improved. With increasing the the amount of SiO2 nano-particles, the water absorption of nano-composites increased, and the thickness swelling reduced.

Since long time ago, researchers in the fields of wood science, dendroclimatology and tree physiology has been interested in the variation of tree-ring width and vessel features within a tree. However, mutual relationship and interplay between these anatomical features were not adequately 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 possess 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, 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 using an image analysis software, tree-ring width (TRW), average vessel lumen area (AVLA), number of vessel in unit 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 the variables at each site, variables 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 both 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 grape tree pruning fibers in combination with wood fibers used in MDF production on contact angle (wettability) and surface bond strength of medium density fiberboard was studied. One layer laboratory panels with the thickness of 15 mm and density of 650 Kg/cm3 were produced. Variable factors were grape tree 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 wettability and surface bond strength of panels were measured. Results showed that the contact angle of the boards was reduced when the grape tree pruning fibers content increased up to 60% and press time up to 6 minutes. In addition, the results indicated that the surface bond strength of panels were reduced with adding grape tree pruning fibers up to 30% whereas the panels produced using 60% grape tree pruning fibers showed stronger bond. Press time did not significantly influence the surface bond strength of panels.

Cellulose is one of the most abundant natural biopolymer on earth which 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) from the bark of the cotton stem was produced by acid hydrolysis in various ratios of 2N hydrochloric acid. Then Nano-crystalline cellulose (NCC) was prepared by chemical methods. The effect of hydrolysis conditions on properties of MCC and NCC such as the crystallinity and crystal size were evaluated using Fourier Transformed Infra-Red Spectroscopy (FT-IR), X-ray diffraction (XRD) and the shape and size of the samples were measured by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Fiber analysis using X-ray showed that increasing the content of acid in the Nano-crystals (NCC) of cotton, the crystallinity of Micro- crystalline cellulose increased but the crystal size did not change Moisture uptake reduced. The crystal size of cotton cellulose was larger than its micro- crystals.

This study was conducted to evaluate stress carrying capacity of miter corner joints fabricated with loose tenon under tension and compression loading. In this study, tests were carried out to determine the effects of the dimension of loose tenon A (3.5´1´0.8 cm) and B (3´2´0.8 cm), type of adhesive, 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 indicated that the stress carrying capacity of joints under compression is higher compared to tension loading. Stress carrying capacity of the joints constructed with loose tenon A was higher than that of B. Furthermore, the results have shown that wood species and type of adhesive had significant effect on the stress carrying capacity. The performance of joints constructed with beech wood and PU adhesive were stronger than joints made of fir wood and PVA adhesive.

In this study, the production of bleached chemi-mechanical pulp from wheat straw for the newsprint production was investigated. Wheat straw was collected from Lorestan province and wheat straw CMP pulp was prepared using 120, 140, and 160oC chemical treatment temperature, 45 minutes time, 10, 12, and 14% chemicals charge and 10: 1 liquor to straw ratio. The yield after defibration treatment varied between 56.5% and 72.5%. Two optimum pulps were bleached using 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% NaOH (based on oven dry weight of the unbleached pulp), 2% H2O2, and 120 minutes time improved the brightness and opacity to 52.9%, and 79.5% ISO, respectively. Optimum pulp strengths including tensile, burst and tear indices were measured as 43.87 Nm/g, 2.18kPa.m2/g, and 8.46mN.m2/g, respectively. All the strengths were higher than newsprint paper strength produced at Mazandaran wood and paper and Korean companies.

In this research, the mechanical and barrier properties of hand-sheets made of virgin and recycled fibers coated by chitosan and poly (vinyl alcohol) polymer blends were studied. In order to evaluate the coating effects on the barrier properties, water vapor transmission rate (WVTR), water absorbance, air resistance and grease proof of coated papers were determined. Mechanical strength including tensile strength and burst strength were also measured. According to the results, the barrier properties and mechanical strength of coated papers improved dramatically compared to uncoated samples. The best results in WVTR and mechanical strength tests were obtained for coatings with the equal 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 layered particleboards were made at 0.7 g/cm3 board density and 16 mm thickness. After conditioning and preparing the 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. 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.