Browsing by Author "Gulec, H. A."

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Evaluation the Kinetic of Peroxide and Hexanal Formation in Ascorbyl Palmitate Incorporated Sunflower Oil During Accelerated Oxidation
(Consejo Superior investigaciones Cientificas-csic, 2024) Kavran, P.; Yucel, T.; Bakkalbasi, E.; Gulec, H. A.; Cavidoglu, I.
The effects of temperature (40-80 degrees C), time (0-28 days), and different concentrations (0-1000 mg/kg) of ascorbyl palmitate (AP) on peroxide value, conjugated diene, triene acids and hexanal contents in sunflower oil kept under accelerated oxidation conditions have been evaluated. Samples with added AP showed lower peroxide values and hexanal contents than their counterparts without AP. While with increasing temperature, the reaction orders for peroxide formation reduced from first to zero order, those for hexanal formation were found to be first order under different experimental conditions. AP reduced the reaction rate constant for peroxide and hexanal formation. The activation energy required for peroxide and hexanal formation ranged from 14.64-89.40 and 1.62-12.14 kJ/mol K, respectively. 400 mg/kg AP, providing the highest activation energies for peroxide and hexanal formation, was found to be the best concentration to enhance the oxidative stability of sunflower oil under defined conditions.
Oxygen Plasma Treatments of Jute Fibers in Improving the Mechanical Properties of Jute/Hdpe Composites
(Elsevier Science Sa, 2011) Sever, K.; Erden, S.; Gulec, H. A.; Seki, Y.; Sarikanat, M.
The surfaces of jute fabrics have been oxygen plasma treated using low frequency (LF) and radio frequency (RF) plasma systems at different plasma powers (30, 60, and 90 W) for 15 min to improve the mechanical properties of jute fiber/HDPE (high density polyethylene) composites. The effect of oxygen plasma treatment on the functional groups of jute fibers was examined by X-ray photoelectron spectroscopy (XPS) analysis. Effects of oxygen plasma treatments on the mechanical properties of jute fiber/HDPE composites were investigated by means of tensile, flexure, and short-beam shear tests. Surface morphology of the fractured surfaces of composites was observed by using scanning electron microscopy (SEM). When RF plasma system was used, the interlaminar shear strength (ILSS) values of the composites increased with increasing plasma power. Similarly, in LF plasma system, ILSS values showed a tendency to increase at plasma powers of 30 and 60 W. However, increasing of plasma power to 90 W decreased the ILSS value of jute/HDPE composite. Also, tensile and flexure strengths of the composites showed similar trends. (C) 2011 Elsevier B.V. All rights reserved.