مجله صنایع چوب و کاغذ ایران
سال سوم شماره 1 (بهار و تابستان 1391)

Study on collapsibility of oriental beech (Fagus orientalis) and paulownia (Paulownia fortune) woods due to their hydrothermal modification as well as the wettability and the water absorption were the main concerns of this research work. Out of these species، blocks of sizes 50×6×6cm were prepared and treated at temperatures of 130 and 150°C with a holding time of 30min in a stainless steel reactor containing the water. Oven dried weights and dimensions of the blocks were measured before and after the hydrothermal treatment to determine the density، collapsibility and mass loss due to applied treatment. Furthermore، small blocks of the treated wood were prepared and soaked in water for 1000-hr to determine their water absorption. The wettability of the woods were also measured to determine the water repellency. Results revealed that any raise of treatment temperature up to 150°C increases the density and the collapsibility. Treated wood collapsed in all directions; however، tangential collapse was much worse than the other directions. The contact angle was increased by rise of the treatment temperature. Hydrothermal treatment has reduced water absorption and increased the hydrophobicity of the woods.

Shortages of raw wood materials and increasing demand for this raw material، has created challenges for wood working industries. These situation makes wood industries to use wood of fast growing species، such as Paulownia. Expanding plantations of paulownia is a feasible solution، but this species owns a low specific gravity and mechanical properties as well. In this research effects of compreg– impregnated (by phenol for maldehyde resin) treatment on improving mechanical properties of paulownia was studied. Test materials were compressed in tangential and radial directions by 3، 30، 40 and 50 percent at 170 ˚c temperature for 12 minute. Specimens were cut from treated test materials and tested according to Iso-3133 & 3787. Result have shown that resin treatment improves all mechanical properties except toughness. Control specomens had higher toughness as compared with treated ones. MOE and MOR did increase، and turned to be highest specomens compressed 50 % in redial direction.

In this research، recycled Old Newsprint (ONP) and glass fiber in mixture rates of 0-50 percent were mixed with Polypropylene (PP) at two levels of 60 and 50 percent (by weight). Physical and mechanical properties of resulted composites were determined. Results have shown that treatments No. 2 (10% glass fibers، 30% ONP and 60% PP) and No. 10 (40% ONP and 60% PP) had totally best physical and mechanical properties on the basis of normalization equation. In addition، the effect of maleic anhydride-Polypropylene coupling agent (MAPP) at two levels of 0 and 4 percent on the physical and mechanical properties of the composites in two optimum treatments was investigated. Results showed that the values of the modulus of elasticity in tension، modulus of rupture، modulus of elasticity in bending and toughness were increased while water absorption and thickness swelling decreased by addition of MAPP. In other words، using MAPP will improve the physical and mechanical properties of such composite.

Acoustic properties of composite boards made out of bagasse were studied in this research. Urea-formaldehyde (UF) and melamine-urea-formaldehyde (MUF) adhesives were used to produce homogeneous as well as three-layered insulating boards with three densities of 0. 3، 0. 4، and 0. 5 g/cm3. The sound absorption coefficient of experimental was measured at five frequencies of 250، 500، 1000، 2000، and 4000 Hz. Results have indicated that the sound absorption coefficient increases as the frequency is increased up to 2000 Hz; further increase in the frequency resulted in decrease in the coefficient. Two type of resins UF and MUF didn''t show significant difference in sound absorption. Boards with lower density absorbed less at lower frequencies; however، increase in the density of the boards resulted in the increase in their sound absorption. Furthermore، layered boards resulted in more sound absorption coefficients at lowest frequency of 250 Hz. Higher frequencies، though، have shown more absorption coefficient. It can be concluded that composite boards made of bagasse can be recommended for production of insulating or sound-proof boards

In this research، effects of using nanoclay on withdrawal strength of screw and nail and also water absorption of nanoclay-MDF dust-PP composite were investigated. Hence، sanding dust of MDF used as lignocellulose material and polypropylene as the thermoplastic material. Also، nanoclay of Cloisite® 15A was used in three different weights 2%، 4% and 6%. At first، raw materials were produced using extruder to fabricate granules. Then، 36 boards (12 treatments in 3 replicates) with nominal density of 1 gr/cm3 and dimensions of 30 cm by 20 cm by 1 cm were produced using hot molding method. Afterwards، samples were conditioned at room temperature conditions for 3 weeks. Then، withdrawal strengths of nails and screws were measured according to BS Standard (CEN/TS15534–1:2007). Also، water absorption and thickness swelling of samples were determined. Results showed that the withdrawal strengths of nails and screws decreases as MDF dust weight is increased. Maximum withdrawal strengths of nails and screws were obtained with 2% of nanoclay. Furthermore، increasing percentage of dust weight as well as nanoclay particles water absorption and thickness swelling of samples are reduced.

In this research، effects of different factors in the CNC machine through- Hole boring of MDF and particleboard were investigated. Variables in boring were selected bit diameter in 3 levels 5،10 and 15 mm، feed speed in 2 levels 0. 3 m/min and 0. 6 m/min and rotary speed of machine axis in 3 levels 300،1500 and 3000 rmp. The goal of this study was to measure effects of mentioned factors on edge- quality of through- holes made in particle- board and MDF. Results have shown that with all bit diameters used، increasing rotary speed of bit improves smoothness of holes in both sides and boring dusts turned to finer sizes. Increasing feed speed did show positive effect on edge surface quality and lowered burr formation.

Earthquake is the major Natural disaster in Iran which once a while causes widespread death and financial losses. Constructional system and materials used in them، most often accelerate these damages، so these are considered principal reasons of the events. Countries that have regions of high seismicity، conducted research on constructional systems، materials، and methods of improving their resistance to earthquake. These research efforts have found simple solution of the problem in wood and its proper combinations with other constructional materials. In this research، regarding such target، two subjects were studied. A model of light framed one story single-family residential house in Iran was constructed to determine its dynamical behavior. The model was constructed in one- third scale of a unit with 54 square meters in base. Foundation anchorage in model was made by metal angle pieces، which were bolted to lower plank. These types of connectors could easily be fabricated in metal working shops in Iran. The rest of joints in model were made with bolts and common nails. To see the behavior of the model، its natural frequency، acceleration at different points، lateral movements (displacement)، and also response of joints to tensile and compressive forces (developed due to lateral dynamical loading on a shaking table) were measured and analyzed. Results have shown that with respect to Fast Fourier Transformation spectra، ratio of maximum acceleration in roof to bottom of model، in sinusoidal acceleration test، the natural frequency of model is ten HZ (fn = 10 Hz)، since 10 Hz frequency has the highest amplitude. This result had contingency with data of sinusoidal acceleration records with 10 HZ frequency and 0. 64 g as well. Therefore، stiffness of model structure would be 78،250 Kg/cm. In addition، results of several sinusoidal acceleration tests for determining delay damping، has shown on the average 0. 039 for this quantity. Brief results of sinusoidal acceleration test، sweeping frequency and time history of Kobe and Tabas earthquake have shown that maximum displacements (lateral movement due to dynamic loading) are related to this acceleration with 8 HZ frequency and 1. 18 g. This displacement in model has been measured 0. 76 mm، which is lower than allowable limit in IBC code (1% of story high، that is، 30 mm for a 3 m high). Including scale coefficient of constructed model، this figure would be 5. 76 mm. But for force، it could be considered that highest tensile and compressive force would occur with 10 HZ frequency and 0. 85g test. The cause is resonant phenomena in this frequency. Therefore، in resonant phenomena maximum force is applied to joints and in this case، each joint would be under load of 30% of building’s weight. Therefore، well-installed joint can considerably prevent death and financial damages. financial losses. Constructional system and materials used in them، most often accelerate these damages، so these are considered principal reasons of the events.

Cellulose fibers undergo a series of irreversible changes i. e hornification when exposed to cycles of wetting and drying. In this study، the effect of recycling on physical and chemical properties of chemimechanical pulp (CMP) and neutral sulfite semi-chemical (NSSC) pulp was evaluated. The pulps were recycled three times. Hornification was measured by Water retention value. The results indicated that water retention value and carboxyl groups were decreased due to recycling، hornification also increased during cycles of wetting and drying. Changes in crystalline structure of the pulp during first cycle of recycling were investigated by ATR- FTIR. The crystallinity index increased to some extent، when compared to virgin pulp. Recycling influence on the fiber length was not significant. Hornification introduced as a main cause of poor properties of recycled paper. Also، reduction of carboxyl groups could be one of the causes for lowering water retention value and decrease in strengths.

Present study conducted to review effects of heat treatment on weight loss، water adsorption، and thickness swelling of poplar (Populus nigra) and beech (Fagus oreintalis) woods impregnated with nano-copper and nano-silver. Specimens werepressur (2. 5 bar) impregnated with 400 PPM water-based solution of nano-copper and nano-silver particles in a pressure vessel. For heat treatment، nano-cupper، nano-silver impregnated and control specimens، were heat treated at 145°C temperature for 24 hours. Water absorption and thickness swelling decreased in heat treated and nano-heat treated specimens and this decrease in specimens impregnated with nano-copper and nano-silver was more obvious than in heat treated control specimens. The reasons were the degradation in crystal sections of celluloses chains and the ink variation of wood polymers. On the other hand، a comparison between heat treated and nano- heat treated specimens has shown weight loss further in nano-heat treated specimens. This shows that retent nano-copper and nano-silver by impregnation facilitates heat transfer in wood; and it may increase the process of degradation and pyrolysis of wood structures in inner parts of specimens.

In this study، effects of natural and artificial veneer on flexural creep behavior of particleboard was investigated. Particleboard panels were prepared from Pars Neopan industries with 660 kg/m3 density and then overlaid by natural and melamine veneers. Their creep behavior was compared to control particleboard. For evaluating maximum bending load in static flexural test، specimens were cut from panels according to ASTM D 1037 with dimensions of 370×50×16 mm. Then، The flexural creep tests at 20% and 40% of failure bending load was applied to test specimens. Results of flexural tests indicated that the MOR and MOE values of veneered particleboard were highest. Results of creep showed that levels of stresses are effective on all creep parameters، but showed less effect on relative creep. Also، creep parameters less effective on specimens overlaid by natural veneer.