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排序方式: 共有163条查询结果,搜索用时 31 毫秒
111.
112.
Some of the properties of oriented strandboard manufactured using kraft lignin phenolic resin 总被引:1,自引:0,他引:1
Ayfer Donmez Cavdar Hulya Kalaycioglu Salim Hiziroglu 《Journal of Materials Processing Technology》2008,202(1-3):559-563
Kraft lignin phenol formaldehyde resin has certain advantages as a binder in oriented strand board manufacture over the other commercially exterior resins. Since kraft lignin is used as substitute for almost 50% phenol in a typical resin, kraft lignin phenol formaldehyde is not only environmentally friendly but also less expensive as compared to other exterior binders used in wood composite industry. The objective of this study is to evaluate the potential of such resin to produce experimental oriented strandboard panels. Aspen (Populus Euroamericana cv.) was used as raw material to manufacture panels under the laboratory conditions. Bending properties including modulus of elasticity, modulus of rupture, internal bond strength, thickness swelling, and water absorption of the samples were determined. Panels made using two types of resins, namely kraft lignin phenol formaldehyde resin and phenol formaldehyde for the control samples. Average modulus of elasticity and modulus of rupture values of the control samples were determined as 2400 N/mm2 and 22.03 N/mm2, respectively. Corresponding values for the panels produced using kraft based resin were 2539 N/mm2 and 20.33 N/mm2. Based on the initial findings of the study both mechanical and physical properties of the panels were not adversely influenced by modified resin. It appears that kraft lignin phenol formaldehyde resin has some potential for oriented strandboard manufacture. Test results revealed that all properties met the minimum requirements specified in related standards and comparable to those commercially manufactured oriented strandboard panels. 相似文献
113.
Serap Doan Pnar Turan Mehmet Doan Mahir Alkan & Oktay Arslan 《International Journal of Food Science & Technology》2008,43(7):1316-1322
Inhibition kinetics and mechanism of polyphenol oxidases (PPO) partially purified from various sources such as Thymbra spicata L. var. spicata and Ocimum basilicum L., and of mushroom PPO bought from Sigma by diethyldithiocarbamic acid have been described using catechol, 4-methylcatechol and pyrogallol as substrates. The inhibition type was competitive for O. basilicum L. PPO using catechol and 4-methylcatechol as substrates, for mushroom PPO using catechol, 4-methylcatechol and pyrogallol as substrates, and for T. spicata L. var. spicata PPO using 4-methylcatechol as a substrate; uncompetitive inhibition for T. spicata L. var. spicata PPO using pyrogallol as a substrate; and non-competitive inhibition for O. basilicum L. and T. spicata L. var. spicata PPO using pyrogallol and catechol as substrates, respectively. The inhibition effect of diethyldithiocarbamic acid on enzymatic browning varied greatly from one phenol to another and from one enzyme to another. Hence, no general rule can easily be established with regard to the type of inhibition observed. 相似文献
114.
Serap Doğan Pınar Turan Mehmet Doğan Oktay Arslan Mahir Alkan 《European Food Research and Technology》2007,225(5-6):865-871
Peroxidase (EC 1.11.1.7; donor: hydrogen-peroxide oxidoreductase) catalyses the oxidation of various electron donor substrates
(e.g. phenols, aromatic amines). In this study, the peroxidase was extracted from Thymbra spicata L. var. spicata and, then partially purified with (NH4)2SO4 precipitation and dialysis. The substrate specificity of peroxidase was investigated using 2,2′-azino-bis(3-ethylbenz-thiazoline-6-sulfonic
acid) (ABTS), o-dianisidine, o-phenylenediamine, catechol and guaiacol as substrates. Furthermore, the effects of buffer concentration, pH, temperature
and thermal inactivation on enzyme activity were also studied. The results obtained have shown that (i) the best substrate
is o-dianisidine, followed by ABTS, catechol, guaiacol and o-phenylenediamine, respectively; (ii) the best buffer concentration is 40 mM for o-dianisidine and catechol, 10 mM for ABTS and guaiacol, and 100 mM for o-phenylenediamine; (iii) optimum pH is 2.5 for ABTS and o-phenylenediamine, 6.0 for o-dianisidine, and 7.0 for catechol and guaiacol; (iv) optimum temperature is 20 °C for catechol, 40 °C for ABTS, guaiacol
and o-dianisidine, and 50 °C for o-phenylenediamine; and (v) the enzyme activity in the thermal inactivation experiments was enhanced with increase in temperature
with o-dianisidine as a substrate while its activity decreased with o-phenylenediamine. 相似文献
115.
A differential low pressure gas flow technique has been developed for the measurement of the mean pore size of membrane filters. The method is here applied to the pore size determination in a range of commercial micro-porous polymer films with pore diameters ranging from 0.03 to 0.8 μm ('Nuclepore'). The polymer films were also examined using scanning electron microscopy so that structural and physical parameters could be evaluated. Two flow regimes could be demonstrated for the permeability data with clear separation between diffusional (Knudsen) flow and viscous or transitional flow occurring at a pore size of 0.2 μm. Alternative theoretical treatments are required for the two regimes but mean pore diameters could be calculated with reasonable precision and agreed with the results obtained by microscopy. In the case of viscous flow it is necessary to assume that the membranes have a tortuosity of less than unity and this is shown to be justified from a consideration of the structure of the pore in the plastic film. 相似文献
116.
Mahir Alkan M. Muhtar Kocakerim Sabri olak 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1985,35(7):382-386
The dissolution kinetics of original and calcinated samples of the boron containing mineral colemanite, in CO2-saturated water were studied. Effects of particle size, calcination temperature and reaction temperature were evaluated. It was observed that the dissolution is chemically-controlled. The reaction rate decreased with increase in particle size, and increased with increase in the calcination and reaction temperatures. The activation energy for solution of the sample calcinated at 400°C as calculated as 57.7 kJ mol?1. 相似文献
117.
The kinetics and mechanism of methylene blue adsorption on perlite have been studied. The effects of various experimental parameters, such as initial dye concentration, temperature and pH on the adsorption rate were investigated. Adsorption measurements show that the process is very fast and physical in nature. The extent of the dye removal increased with increase in the initial concentration of the dye and the initial pH and temperature of solution. Adsorption data were modelled using the first and second-order kinetic equations, mass transfer and intra-particle diffusion models. It was shown that the second-order kinetic equation could best describe the sorption kinetics. The diffusion coefficient, D, was found to increase when the initial dye concentration, pH and temperature were raised. Thermodynamic activation parameters, such as DeltaG*, DeltaS* and DeltaH*, were calculated. 相似文献
118.
119.
Ümit Alkan Mehmet Kılıç Yaşar Karabul Mustafa Çağlar Orhan İçelli Zeynep Güven Özdemir 《应用聚合物科学杂志》2018,135(31)
In this study, the influences of polypropylene (PP) additive (varying from 20% to 80% wt) and low dose X‐ray irradiation (changing from 25 to 100 Gy) on the mechanical and dielectric properties of low‐density polyethylene (LDPE) were investigated. LDPE/PP film blends were prepared by hot press technique. While the highest Young modulus and tensile strength were observed for the 20%LDPE/80%PP blend at 25 Gy X‐ray irradiation, the same blend had the highest energy at break and percentage strain at break values for 50 Gy X‐ray exposure. These results also indicated a chain scission in the material. The differential scanning calorimetry curves also indicated a chain scission and crosslinking effects in the blends due to X‐ray irradiation. Hence, the higher concentration of PP additive and exposure of low dose X‐ray resulted in a polymer composite with high mechanical performance. On the other hand, the dielectric investigations revealed that the 25 Gy X‐ray irradiated 20%LDPE/80%PP blend may also attract attention for capacitor applications due to its increased static dielectric constant and reduced dielectric loss. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46571. 相似文献
120.
Amir Navidfar Alkan Sancak Kemal Baran Yildirim Levent Trabzon 《Polymer-Plastics Technology and Engineering》2018,57(14):1463-1473
Multifunctional polyurethane foams reinforced with multiwalled carbon nanotubes and silica nanoparticles enhanced specific properties. We studied the effects of nanoparticle addition into polyurethane on mechanical properties and thermal stability by means of tensile, Charpy impact, hardness tests, and thermogravimetric analysis. Nanoparticles added to polyurethane are multiwalled carbon nanotubes, two types of silica nanoparticles, and multiwalled carbon nanotube/spherical silica as hybrid filler. Hybrid polyurethane/spherical silica/multiwalled carbon nanotube nanocomposite with the constant overall content of 0.75?wt% showed higher tensile strength, hardness, and thermal stability than either of nanoparticles at this content, which approves a synergistic effect between multiwalled carbon nanotubes and silica nanoparticles. 相似文献