Management and Economics wood
Fatemeh Hasani Khorshidi; Mehdi Emadi
Abstract
In this study, effect of accelerated aging on adhesion strength of half-polyester and polyurethane transparent coatings were evaluated in maple and pine species. For this purpose, dried specimens with 12×110×550 millimeters were used. Sealer as substrate, and half-polyester and binary polyurethane ...
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In this study, effect of accelerated aging on adhesion strength of half-polyester and polyurethane transparent coatings were evaluated in maple and pine species. For this purpose, dried specimens with 12×110×550 millimeters were used. Sealer as substrate, and half-polyester and binary polyurethane as coatings were applied on wood. Coatings were implemented thereby film applicator and gun methods, and accelerated aging test of wood specimens was carried out according to ASTM D1037. Results indicated that maximum value of adhesion strength is belong to binary polyurethane in maple applied by film applicator and minimum for half-polyester in pine applied by gun method, in opposite. Due to thin film, velocity variations in gun method by painter person, and consequent rapid evaporation of thinner, adhesion decreased in comparison with film applicator method. Also it's found that accelerated aging diminished adhesion strength of coatings in both maple and pine species. It can be concluded during the accelerated aging test, the steam causes moisture absorption and swelling of the fibers near the surface and thus reduce the resistance of the coating adhesion.Long-term effect of humidity and aging makes Ecowool quickly lose their stickiness.And the effect of floating in the water samples, lignin degradation products in the process of steaming and freezing and heating washed by water And cause the loosening of the cellulosic fibers in the wood, resulting in wood adhesive strength is significantly reduced due to the accelerated aging test.
Salehe Nazari; Noraldin Nazarnezhad; Mohammad Ali Ebrahimzadeh
Abstract
Plants are a rich source of phenolic compounds as natural antioxidants. Antioxidants are the main factors in neutralizing free radicals and prevent the spread of diseases and destruction of many foods. These compounds are extractable from the bark of Eucalyptus camaldulensis and Pinus sylvestris trees. ...
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Plants are a rich source of phenolic compounds as natural antioxidants. Antioxidants are the main factors in neutralizing free radicals and prevent the spread of diseases and destruction of many foods. These compounds are extractable from the bark of Eucalyptus camaldulensis and Pinus sylvestris trees. The purpose of this study was to evaluate the antioxidant properties and total phenolic and flavonoids of Eucalyptus and pine wood bark. After preparation of the bark, ethanol extracts were extracted using soxhlet extractor. First the amount of total phenol and flavonoids of the extract was measured. Then to evaluate antioxidant properties of the extracts, four methods include Diphenyl Picryl Hydrazyl, reducing power; nitric oxide and metal chelating activity were used. The results showed that total phenol and flavonoid content, in eucalyptus bark was higher than pine. Test results to trap free radicals of diphenyl Pykryl Hydrazyl showed that 50% inhibitory concentration of ethanol extract of the Eucalypt and Pine bark values as 3.02 and 15.77 micrograms per milliliter, respectively. Also, in reducing power test, absorption rate for eucalyptus bark extract was higher than the pine. In nitric oxide trap test, 50% inhibitory concentration in ethanol extract of eucalypt bark was measured as 2.41 and in pine extract was 22.75 micrograms per milliliter. Furthermore, the results of Fe2+ chelating ability of ethanol extract of eucalyptus and pine bark at a concentration of 100 micrograms per milliliter inhibited 37 and 97/18 percent respectively. Ethanol extracts of the eucalypt and pine bark in four case study tests, showed an acceptable antioxidant activity. Thus, these compounds can be regarded as good sources ofnatural antioxidants.