Mohamad Tasoji; Taghi Tabrsa; Alireza Mohammadi
Abstract
For making wheat straw particleboards, different mixtures of UF and MF resins were used. The ratio of UF : MF was 0:100,75:25,50:50,25:75 and 100:0 based on weight of resin and boards densities were set to 0.7 . The physical and mechanical properties such as Thickness Swelling(TS)(after 2 and 24 hours), ...
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For making wheat straw particleboards, different mixtures of UF and MF resins were used. The ratio of UF : MF was 0:100,75:25,50:50,25:75 and 100:0 based on weight of resin and boards densities were set to 0.7 . The physical and mechanical properties such as Thickness Swelling(TS)(after 2 and 24 hours), Internal Bonding(IB) , Modulus Of Elasticity(MOE) ,Modulus Of Rupture(MOR) were determined and compared to EN 312-4 standard. The highest amounts of IB ,MOR and MOE are from the boards that were made from 50:50 (UF:MF) . All of The boards MOE and MOR amounts of all treatments except treatment 100:0 (UF:MF) were in range of EN 312-4 standard but the IB amounts were not. The TS amount was improved in the boards with more MF content but it was not in EN 312-4 range. Due to the thin waxy layer that covers the outer most layer of wheat straw surface, the non polar structure of this layer brings incompatibility between polar resins and wheat straw particles and this incompatibility will result in low physical and mechanical property for wheat straw particleboards. Also due to low porosity of waxy layer, the distribution of formaldehyde polar resins on straw particles surface, not well occur and this itself is an important factor in decrease of physical and mechanical resistance in wheat straw particleboards.
Composite wood products
Taghi Tabarsa; Sayed mohammad Hosseini; Eiman Valizadeh
Abstract
This study was conducted to investigate the potential of waste newspaper application in cement fiber board production. Cement fiber board were produced using three levels of waste paper fibers and two levels of calcium chloride as additive material. After making the boards, the Modulus of Rupture (MOR) ...
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This study was conducted to investigate the potential of waste newspaper application in cement fiber board production. Cement fiber board were produced using three levels of waste paper fibers and two levels of calcium chloride as additive material. After making the boards, the Modulus of Rupture (MOR) and thickness swelling after 24 hours immersion in water were determined based on DIN 68763. The results showed that boards made with cement:fiber ratio 90:10 and 5% calcium chloride exhibited the maximum modulus of rupture and minimum of thickness swelling (TS) after 24 hours. The results also showed that additive material had positive effect on physical and mechanical properties of boards.
Physics and Mechanical Wood
Alireza Mohammadi; Taghi Tabarsa; Mohammad Tasoji
Abstract
In this paper effect of static densification of treated paulownia on relationship between strength properties and density was investigated. Specimens were steamed at 130 and 170oc and immediately were compressed to 35% and 45% of their original thickness in radial direction. Mechanical properties such ...
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In this paper effect of static densification of treated paulownia on relationship between strength properties and density was investigated. Specimens were steamed at 130 and 170oc and immediately were compressed to 35% and 45% of their original thickness in radial direction. Mechanical properties such as bending strength, brinell surface hardness and compression strength in axial and radial direction were determined for non-densified and densified wood. Indexes of density, strength, quality and strength potential were calculated to study the relationship between strength and density. The results show that the density index and strength index and also strengths significantly increased with increase in densification but strength potential indexes decreased. Steam treatment at 130oc had a slight positive effect on the strengths and strength potential indexes as effect of softening the wood but the strength potential indexes and strengths decreased due to treatment of wood at 170oc. Generally, strength potential indexes of all tested mechanical properties show that strength of densified paulownia was lower compared to what had expected for non-densified paulownia from increasing density, which in turn demonstrate the cell walls were negatively affected by compression. Axial compression strength and brinell hardness were slightly affected by densification.
Alireza Mohammadi; Taghi Tabarsa; Mohammad Tasooji
Abstract
The effect of amino silane coupling agent on properties of wheat straw boards produced by UF and MF resins, was investigated in this study. For producing the straw boards small particles of straw were used . The results showed that adding 2 and 5 percents of silane had significant effect on improvement ...
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The effect of amino silane coupling agent on properties of wheat straw boards produced by UF and MF resins, was investigated in this study. For producing the straw boards small particles of straw were used . The results showed that adding 2 and 5 percents of silane had significant effect on improvement of boards properties. This improvement might be due to surface treatment of wheat straw particles with silane coupling agent by increasing the bondability between straw particles and resin. The more amine groups in Melamine Formaldehyde resin compare to urea formaldehyde resin , lead to an improvement in bending strength and thickness swelling.
Composite wood products
Hamid reza Adalat; Taghi Tabarsa; Marzyeh Raeisi
Abstract
For this study 10 logs of Paullowina.furtunie from Shastkalateh forest of Gorgan in Iran were selected randomly. After that, 45 clear flat swan specimens prepared and dried to 5% moisture. Density of each log and thickness of specimens were measured. Three levels of compression percent (16%, 33% and ...
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For this study 10 logs of Paullowina.furtunie from Shastkalateh forest of Gorgan in Iran were selected randomly. After that, 45 clear flat swan specimens prepared and dried to 5% moisture. Density of each log and thickness of specimens were measured. Three levels of compression percent (16%, 33% and 50%) and temperature (130°C, 145°C and 160°C) were the variables. The physical properties of specimens such as spring back, compression set and thickness swelling were calculated. Also, MOE, MOR and impact resistance of specimens were evaluated. In order to have accurate examination, microscopic images were taken. Results show that, with increasing in compression percent, the amounts of spring back and thickness swelling enhance. Densification with 16% compression, yields deformation in elastic region while 33% and 50% compression, causes more compression set. The more compression percent, the more mechanical strengths and the highest strength attained in 50% compression. The effect of temperature was insignificant mostly. Finally, the proper treatment for Paullownia densification, was 130°C and 50% compression. Microscopic images asserted the above results and illustrated that, the enhancing of densification above 50% compression is possible.
Composite wood products
Amir Nourbakhsh; Taghi Tabarsa; Abolfazl Kargarfard; Fardad Golbabaei
Abstract
Laminated veneer lumber (L. V. L) manufactured from Maple and Alder wood is investigated. Three levels of layer thicknesses of 2, 3 and 4mm. were investigated. Bending strength (MOR and MOE), CompressionThe results of this investigation indicated that laminated wood strength of samples produced from ...
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Laminated veneer lumber (L. V. L) manufactured from Maple and Alder wood is investigated. Three levels of layer thicknesses of 2, 3 and 4mm. were investigated. Bending strength (MOR and MOE), CompressionThe results of this investigation indicated that laminated wood strength of samples produced from Alder layers are superior to Maple. Statistical analysis of the results showed that the effect of wood species on strength properties was significantly different at 99% level. Layer thicknesses also showed significant effect on strength increasing layer thicknesses from 2 to 4 mm. caused a reduction on MOE and improved impact properties.The results of this investigation also showed that Alder layers at 4 mm. Is superior to Maple layers in impact properties.
Composite wood products
Ahmad Jahan latibari; Abdolrahman Hosseinzadeh; Taghi Tabarsa
Abstract
In this investigation, the effect of mat moisture content, press temperature and time on polymerization reaction of urea-formaldehyde (UF) resin and the strength of UF bonded hornbeam particleboard is studied. Variation of three variables is as followed:
-mat moisture content; 10, 13 and 16% (Based ...
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In this investigation, the effect of mat moisture content, press temperature and time on polymerization reaction of urea-formaldehyde (UF) resin and the strength of UF bonded hornbeam particleboard is studied. Variation of three variables is as followed:
-mat moisture content; 10, 13 and 16% (Based on oven dry weight of wood)
-Press temperature; 150, 170 and 190 ᵒC
-Press time; 4, 6, and 8 min.
Fore boards were manufactured for each combination of variables. Modulus of rupture (MOR), modulus of elasticity (MOE), Internal bond (IB), water absorption (Wa2 and Wa24) and thickness swelling (Ts2 and Ts24) after 2 and 24 hours immersion in water were determined according to ASTM 1037 standard. All data was analyzed using factorial design. The effect of mat moisture content on MOR was not statically different, but its effect on MOE was statistically different at 5% significance level, and increasing the mat moisture content from 10 to 16% bout MOR & MOE. Highest level of MOE (4262 MPa) corresponds to board pressed at 16% mat moisture content. On the contrary, mat moisture content decreased the IB and lowest value of IB ( 1.447 MPa) corresponds to boards pressed at 16% mat moisture content. The effect of mat moisture content on IB was statistically different at 1% significance level. Increasing mat moisture content decreased water absorption and increased thickness swelling. Lowest Wa2 & Wa24 was observed on boards pressed at 16% mat moisture content (67.35% & 86.78% respectively) and lowest Ts2 & Ts24 was observed on boards pressed at 10% mat moisture content (21.89% & 27.32% respectively). There force for the production of suitable boards, ma moisture content must be kept at 10-13% range.
