Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 15Citation - Scopus: 18Preparation and Characterization of Magnesium Stearate, Cobalt Stearate, and Copper Stearate and Their Effects on Poly(vinyl Chloride) Dehydrochlorination(John Wiley and Sons Inc., 2015) Gönen, Mehmet; Egbuchunam, Theresa Obuajulu; Balköse, Devrim; İnal, Fikret; Ülkü, SemraPreparation and characterization of pure metal soaps and investigation of their effects on poly(vinyl chloride) (PVC) dehydrochlorination were the objectives of the present study. Magnesium stearate (MgSt2), cobalt stearate (CoSt2), and copper stearate (CuSt2) were prepared by a precipitation method. An aqueous sodium stearate (NaSt) solution was mixed at 500 rpm with respective metal salt solutions at 75oC. The precipitates that formed were collected by filtration, washed with water, and ultimately dried at 105oC under reduced pressure. Lamellar crystals that melted on heating were obtained. Solid-liquid phase transitions were observed by optical microscopy at 160oC, 159oC, and 117oC for MgSt2, CoSt2, and CuSt2, respectively. However, the melting points of MgSt2, CoSt2, and CuSt2 were determined as 115oC, 159oC, and 111oC, respectively, by analysis by differential scanning calorimetry. The onset temperature of the mass loss was the lowest at 255oC for CuSt2 and the lowest activation energy for thermal decomposition was 18 kJ/mol for CuSt2. CoSt2 was effective in extending the induction time of PVC dehydrochlorination at both 140oC and 160oC. The activation energy calculated from stability time decreased from 175 kJ/mol for a blank PVC sample to 114, 105, and 107 kJ/mol for MgSt2, CoSt2, and CuSt2-containing PVC samples, respectively. All three metal soaps accelerated the dehydrochlorination of PVC. J. VINYL ADDIT. TECHNOL., 21:235-244, 2015.Article Citation - Scopus: 1Optical and Surface Properties of Zinc Oxide Nanoparticles Dried by Conventional and Supercritical Ethanol Drying Techniques(Research India Publications, 2014) Egbuchunam, Theresa Obuajulu; Yetgin, Senem; Özmıhçı Ömürlü, Filiz; Balköse, DevrimZinc oxide (ZnO) nanoparticles were synthesized by conventional (ZnO-A) and supercritical ethanol drying (ZnO-B). Nitrogen adsorption/desorption analyses were performed to determine the surface areas of the powders. The specific surface area was 28.30m2/g and 10.61 m2/g for ZnO-A and ZnO-B respectively. The powders adsorbed very small amount of CO2with the conventionally dried powder adsorbing more CO2. Supercritical ethanol dried ZnO had ethanol on its surface which was eliminated by vacuum application at room temperature. Both powders had OH groups which were eliminated on heating up to 500°C under vacuum. However, OH groups were present in lower amounts in supercritical ethanol dried ZnO. The powders were characterized by UV-VIS optical absorption and room temperature photoluminescence spectroscopic analyses. The UV-VIS absorption spectrum showed an absorption band at 375nm due to ZnO nanoparticles. The photoluminescence spectrum of ZnO excited at 380nm exhibited three emission peaks: one at 424nm and 490nm corresponding to band gap excitonic emission and another located at 520nm due to the presence of singly ionized oxygen vacancies.Conference Object Citation - WoS: 23Citation - Scopus: 30Thermal Behaviour of Metal Soaps From Biodegradable Rubber Seed Oil(Springer Verlag, 2010) Balköse, Devrim; Egbuchunam, Theresa Obuajulu; Okieimen, Felix EbhodagheSoaps are a class of surface active compounds derived from natural oils and fats. Double decomposition reactions permit the synthesis of metallic soaps, which are long-chain carboxylates of metal ions, from alkaline ones such as sodium, potassium or ammonium soaps. Metallic soaps are commercially important as they find use in diverse applications such as driers in paints or inks, components of lubricating greases, heat stabilizers for plastics (especially PVC), catalysts and water proofing agents, fuel additives and cosmetic products amongst others. Many of these applications are related to the thermal properties of these compounds and the thermal behaviour of metal soaps in terms of decomposition processes is of great importance. Rubber seed oil (RSO) which is an unsaturated triglyceride abundantly available in Nigeria, India and Australia is an excellent starting material for metal soaps. In this study rubber seed oil having 2.2% myristic acid, 7.6% palmitic acid, 10.7% stearic acid, 20.61% oleic acid, 36.62% linoleic acid, 22.5% linolenic acid was used in making barium, calcium, cadmium and zinc soaps. The thermal behaviour of soaps (Ba, Ca, Cd and Zn) of rubber seed oil for use as additives in the processing of poly(vinyl chloride) (PVC) was investigated by thermal gravimetry and differential scanning calorimetry. The stability of the soaps was examined by thermogravimetry up to 873 K at a constant heating rate of 10 °C min -1. The soaps were found to be thermally stable up to 473 K as they recorded less than 5% mass loss at this temperature with values of apparent activation energy for decomposition varying from 52 to 96 kJ mol-1. Differential scanning calorimetric studies of the soaps revealed melting and decomposition behaviour of metal soaps. © 2010 Akadémiai Kiadó, Budapest, Hungary.Article Citation - WoS: 2Citation - Scopus: 1Stabilizing Effect of Biobased Additives on the Thermal Degradation of Pvc(Trans Tech Publications, 2010) Egbuchunam, Theresa Obuajulu; Okieimen, Felix Ebhodaghe; Balköse, DevrimNovel biobased additives prepared from rubber seed oil were evaluated as thermal stabilizer for PVC. Divalent metal (barium and cadmium) soaps of rubber seed oil were prepared by metathesis in aqueous alcohol and characterized by thermal methods (differential scanning calorimetry and thermogravimetry). The stabilizing effect of the soaps and their admixtures on the thermal degradation of PVC powder and plasticized PVC was examined by dynamic thermogravimetry and dehydrochlorination studies at 160°C using the Thermomat equipment. The metal soaps showed multiple decomposition endotherms but were generally stable (with weight loss less than 5%) within the temperature range (180-220°C) frequently used in the processing of PVC. Using the Broido model, values of apparent activation energy of decomposition of between 50 and 200 kJmol-1 were obtained for the soaps. The biobased additives were found to be relatively effective in stabilizing PVC in powder and plasticized forms against thermal degradation. Using inhibition/retardation time, temperature of incipient decomposition, and temperature at which various extents of decomposition was attained as indices of thermal stabilization, the results from this study indicate a potential for the application of the biobased additives as thermal stabilizer for PVC in rigid and flexible formulations. © (2010) Trans Tech Publications, Switzerland.Conference Object Citation - WoS: 2Citation - Scopus: 2Studies in the Utilization of Biobased Additives as Thermal Stabilizer for Plasticized Pvc(Trans Tech Publications, 2009) Okieimen, Felix Ebhodaghe; Egbuchunam, Theresa Obuajulu; Balköse, DevrimDivalent metal (barium, cadmium, calcium and zinc) soaps of rubber seed oil and their binary mixtures (BaJCd and CaJZn) and epoxidized rubber seed oil (4.5% epoxide content) and its admixtures with the single divalent metal soaps were evaluated as thermal stabilizer for dioctylphthalate plasticized PVC using changes in discolouration indices (yellowness index and UV absorption at 360nm) and initial rates of dehydrochlorination measured at 140 and 160°C. The results obtained showed that the divalent metal soaps were relatively effective in stabilizing the dioctylphthalate plasticized PVC against thermal degradation and that the binary soap mixtures enhanced the heat stabilizing effectiveness: marked reduction in the values of the discolouration indices; longer dehydrochiorination induction period and smaller values of rate constant of initial rate of dehydrochlorination. It was found that epoxidized rubber seed oil was less effective in comparison with the divalent metal soaps in stabilizing plasticized PVC against thermal degradation. These results show that the bio-based additives are compatible with dioctylphthalate plasticized PVC, stable to heat within the range of temperature used in the processing of plasticized PVC, inhibitlretard dehydrochlorination and reduce the extent of degradation.Article Citation - WoS: 15Citation - Scopus: 18Formulation and Properties' Evaluation of Pvc/(dioctyl Phthalate)/ (epoxidized Rubber Seed Oil) Plastigels(John Wiley and Sons Inc., 2008) Balköse, Devrim; Egbuchunam, Theresa Obuajulu; Okieimen, Felix EbhodagheEpoxidized rubber seed oil (4.5% oxirane content, ERSO) was prepared by treating the oil with peracetic acid generated in situ by reacting glacial acetic acid with hydrogen peroxide. The thermal behavior of the ERSO was determined by differential scanning calorimetry. The effect of the epoxidized oil on the thermal stability of poly (vinyl chloride) (PVC) plastigels, formulated to contain dioctyl phthalate (DOP) plasticizer and various amounts of the epoxidized oil, was evaluated by using discoloration indices of the polymer samples degraded at 1600C for 30 min and thermogravimetry at a constant heating rate of 10°C/min up to 600°C. The thermal behavior of the ERSO was characterized by endothermic peaks at about 150°C, which were attributed to the formation of network structures via epoxide groups, and at temperatures above 300°C, which were due to the decomposition of the material. Up to 50% of the DOP plasticizer in the PVC plastisol formulation could be substituted by ERSO without a marked deleterious effect on the consistency of the plastigel formed. In the presence of the epoxidized oil, PVC plastigel samples showed a marked reduction in discoloration and the number of conjugated double bonds, as well as high temperatures for the attainment of specific extents of degradation. These results showed that the ERSO retarded/inhibited thermal dehydrochlorination and the formation of long (n > 6) polyene sequences in PVC plastigels. The plasticizer efficiency/permanence of ERSO in PVC/DOP plastigels was evaluated from mechanical properties' measurements, leaching/migration tests, and water vapor permeability studies. The results showed that a large proportion of DOP could be substituted by ERSO in a PVC plastisol formulation without deleterious effects on the properties of the plastigels.Article Citation - Scopus: 1The Effect of Bio-Based Plasticizer on the Permanence and Water Vapour Transport Properties of Pvc Plastigels(Serbian Chemical Society, 2008) Okieimen, Felix Ebhodaghe; Egbuchunam, Theresa Obuajulu; Balköse, DevrimNovel formulations of PVC plastisols based on blends of bio-based and synthetic plasticizers were prepared and characterized. A traditional phthalate plasticizer, dioctylphthalate, was replaced in the plastisols studied by the epoxidized rubber seed oil (4.5 % oxirane content). The plastisols formed were processed into plastigels and characterized in terms of permanence properties using leaching and migration tests and water vapour barrier properties. It was found that the permanence properties of PVC/DOP plastigels were maintained in the presence of up to 50 % ERSO, and that blending with DOP did not impair the water barrier properties of PVC plastigels.Article Citation - WoS: 56Citation - Scopus: 66Effect of Zinc Soaps of Rubber Seed Oil (rso) And/Or Epoxidised Rubber Seed Oil (erso) on the Thermal Stability of Pvc Plastigels(Elsevier Ltd., 2007) Egbuchunam, Theresa Obuajulu; Balköse, Devrim; Okieimen, Felix EbhodagheZinc soaps of rubber seed oil (RSO) and epoxidised rubber seed oil (ERSO) were prepared and their use as PVC stabilizers investigated. Characterization of Zn soaps of RSO prepared by different techniques and ERSO gave information on the purity, structure and thermal behaviour of these materials. From the analysis, the production of these materials for use in thermal stabilization of PVC would be optimized as their use greatly enhanced the stability of PVC as obtained from the conductivity measurements using the 763 PVC Thermomat. The minimum amount of HCl release was obtained for the samples with Zn soaps and ERSO indicating a synergistic effect. Zn soaps having Zn(OH)2 stabilized PVC better than pure Zn soaps.