Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
Browse
8 results
Search Results
Article Citation - WoS: 2Citation - Scopus: 10Water and Water Vapor Sorption Studies in Poly(propylene)-Zeolite Composites(John Wiley and Sons Inc., 2003) Pehlivan, Hilal; Özmıhçı, Filiz; Tıhmınlıoğlu, Funda; Balköse, Devrim; Ülkü, SemraWater and water vapor sorption to porous poly(propylene)zeolite composites prepared by hot pressing have been studied as a function of zeolite loading. This work presents the first report on the effect of the zeolite as a filler on the water sorption properties of PP composites. Water swelling experiments were conducted at 25°C using pure PP and PP-zeolite film samples having different zeolite loadings (6-40 wt%). Since PP is a hydrophobic polymer, it does not sorp any water, but the composites having 10, 20, 30, and 40% zeolite sorbed 0.63, 1.00, 1.72 and 3.74 wt% water, respectively. The zeolite itself at the same conditions sorbed 24.5 wt% water. As the filler loading in the composites increased, equilibrium uptake values increased too. On the other hand, water vapor sorption and kinetics has been studied using a Cahn 2000 gravimetric sorption system. Within in the range 0.35-0.95%, water vapor was adsorbed by the composites containing 10-40 wt% zeolite. Experimental effective water vapor diffusivities of the composite films were about one order of magnitude higher than the experimental water diffusion coefficient in composites. The transport of water in composites was slower than that in the liquid water due to the longer diffusion pathway and adsorption on the surface of the composites. Although the liquid water may fill all the voids in the composite, water vapor is adsorbed on the surface of the zeolite only.Article Citation - WoS: 96Citation - Scopus: 131Barrier Properties of Corn Zein Nanocomposite Coated Polypropylene Films for Food Packaging Applications(Elsevier Ltd., 2013) Özçalık, Onur; Tıhmınlıoğlu, FundaThe feasibility of corn zein nanocomposite (CZNC) coatings as an alternative to synthetic polymer barrier layer on polypropylene (PP) films was examined. The effect of layered silicate content in the CZNC layers on the barrier and surface hydrophobicity of the CZNC-PP films were investigated. Incorporation of organomodified montmorillonite (OMMT) by solution intercalation into zein matrix significantly improved oxygen and water vapor barrier of coated PP films. The barrier properties were also investigated theoretically by using various phenomenological permeability models. Tortuous permeation path formed by the fine delamination of nanoclays was found to be responsible for the barrier improvements in zein layers. In conclusion, durable CZNC-PP laminates were developed. CZNC coating of PP films has reduced the oxygen permeability nearly four times, while water vapor permeability reduced by 30% with 5 wt.% OMMT content in 5.9 μm corn zein coating.Article Citation - WoS: 11Citation - Scopus: 13Water Vapour Barrier Performance of Corn-Zein Coated Polypropylene (pp) Packaging Films(Springer Verlag, 2008) Atik, İsa Doğan; Özen, Fatma Banu; Tıhmınlıoğlu, FundaThe novel film structure of corn-zein coated on polypropylene (PP) synthetic film for packaging industry was developed to examine the feasibility of resulting coated films as an alternative water barrier performance for food packaging. The effects of coating formulation (solvent, corn-zein, plasticizer concentration and plasticizer type) on final properties of films were observed. Corn-zein is the most important protein of corn and has good film forming property. Composites structures of PP films coated with corn-zein were obtained through a simple solvent casting method. Polyethylene glycol (PEG) and glycerol (GLY) were used as plasticizer to increase film flexibility. Statistical analysis based on full factorial design was performed to observe coating formulation effects. The high water vapour barriers were obtained for films coated with coating formulation consisting of higher amounts of corn-zein plasticized by GLY. The lower glass transition temperatures (T g) of films were obtained by plasticization of films and T g decreased by increasing plasticizer content. The statistical analysis defined the key parameters of coating formulation that had major effects on the final properties of coated PP films as corn-zein, plasticizer concentration and plasticizer type. In conclusion, corn-zein coatings could have potential as an alternative to conventional synthetic polymers used in composite multilayer structures for food packaging applications.Article Citation - WoS: 324Citation - Scopus: 356The Effect of Fiber Surface Treatments on the Tensile and Water Sorption Properties of Polypropylene-Luffa Fiber Composites(Elsevier Ltd., 2006) Demir, Hasan; Atikler, Ulaş; Balköse, Devrim; Tıhmınlıoğlu, FundaThe effects of coupling agents on the mechanical, morphological, and water sorption properties of luffa fiber (LF)/polypropylene(PP) composites were studied. In order to enhance the interfacial interactions between the PP matrix and the luffa fiber, three different types of coupling agents, (3-aminopropyl)-triethoxysilane (AS), 3-(trimethoxysilyl)-1-propanethiol (MS), and maleic anhydride grafted polypropylene (MAPP) were used. The PP composites containing 2-15 wt% of LF were prepared in a torque rheometer. The tensile properties of the untreated and treated composites were determined as a function of filler loading. Tensile strength and Young's modulus increased with employment of the coupling agents accompanied by a decrease in water absorption with treatment due to the better adhesion between the fiber and the matrix. The maximum improvement in the mechanical properties was obtained for the MS treated LF composites. The interfacial interactions improved the filler compatibility, mechanical properties, and water resistance of composites. The improvement in the interfacial interaction was also confirmed by the Pukanszky model. Good agreement was obtained between experimental data and the model prediction. Morphological studies demonstrated that better adhesion between the fiber and the matrix was achieved especially for the MS and AS treated LF composites. Atomic force microscope (AFM) studies also showed that the surface roughness of LFs decreased with the employment of silane-coupling agents.Article Citation - WoS: 18Citation - Scopus: 19Effect of Zeolite Filler on the Thermal Degradation Kinetics of Polypropylene(John Wiley and Sons Inc., 2006) Pehlivan, Hilal; Balköse, Devrim; Ülkü, Semra; Tıhmınlıoğlu, FundaIn this study, the thermal degradation behavior of polypropylene (PP) and PP-zeolite composites was investigated, Clinoptilolite, a natural zeolitic tuff, was used as the filler material in composites. The effects of both pure clinoptilolite and silver-ion-exchanged clinoptilolite on the thermal degradation kinetics of the PP composites was studied with differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Polymer degradation was evaluated with DSC at heating rates of 5, 10, and 20°C/ min from room temperature to 500°C. The silver concentration (4.36, 27.85, and 183.8 mg of Ag/g of zeolite) was the selected parameter under consideration. From the DSC curves, we observed that the heat of degradation values of the composites containing 2-6% silver-exchanged zeolite (321-390 kj/kg) were larger than that of the pure PP (258 kj/kg). From the DSC results, we confirmed that the PPzeolite composites can be used at higher temperatures than the pure PP polymer because of its higher thermal stability, The thermal decomposition activation energies of the composites were calculated with both the Kissinger and Ozawa models. The values predicted from these two equations were in close agreement. From the TGA curves, we found that zeolite addition into the PP matrix slowed the decomposition reaction; however, silver-exchanged zeolite addition into the matrix accelerated the reaction. The higher the silver concentration was, the lower were the thermal decomposition activation energies we obtained. As a result, PP was much more susceptible to thermal decomposition in the presence of silver-exchanged zeolite.Article Citation - WoS: 187Citation - Scopus: 208Synergistic Effect of Natural Zeolites on Flame Retardant Additives(Elsevier Ltd., 2005) Demir, Hasan; Arkış, Esen; Balköse, Devrim; Ülkü, SemraThe thermal degradation and flammability of intumescent fire-retardant polypropylene matrix composites consisting of ammonium polyphosphate (APP) as an acid source and blowing agent, pentaerythritol (PER) as a carbonisation agent and natural zeolite (clinoptilolite rich, Gördes II) as a synergistic agent were examined. APP and PER combinations were examined at different ratios (0.25, 0.33, 0.5, 1, 2, 3, and 4) for optimisation of the formulation for flame retardancy. The zeolite was incorporated into flame retardant formulation at four different concentrations (1, 2, 5, and 10 wt%) to investigate the synergism between the flame retardant materials. The thermal degradation and flammability of composites were characterized by thermogravimetric analysis (TGA) and by limiting oxygen index (LOI) measurement and horizontal burning (HB) tests. A synergistic effect in flame retardancy was observed when natural zeolites were used in combination with APP and PER.Article Citation - WoS: 183Citation - Scopus: 190The Effect of Interfacial Interactions on the Mechanical Properties of Polypropylene/Natural Zeolite Composites(Elsevier Ltd., 2004) Metin, Dildare; Tıhmınlıoğlu, Funda; Balköse, Devrim; Ülkü, SemraThe effect of interfacial interactions on the mechanical properties of polypropylene (PP)/natural zeolite composites was investigated under dry and wet conditions. Interfacial interactions were modified to improve filler compatibility and mechanical properties of the composites by surface treatment of natural zeolite with a non-ionic surface modifier; 3 wt% polyethylene glycol (PEG) and three different types of silane coupling agents; 3-aminopropyltriethoxysilane (AMPTES), methyltriethoxysilane (MTES) and 3-mercaptopropyltrimethoxysilane (MPTMS), at four different concentrations (0.5-2 wt%). PP composites containing (2-6 wt%) zeolite were prepared by an extrusion technique. The tensile properties of the composites determined as a function of the filler loading and the concentration of the coupling agents were found to vary with surface treatment of zeolite. Silane treatment indicated significant improvements in the mechanical properties of the composites. According to the dry and wet tensile test results, the maximum improvement in the mechanical properties was obtained for the PP composites containing 1 wt% AMPTES treated zeolite. The improvement in the interfacial interaction was confirmed using a semi-empirical equation developed by Pukanszky. Good agreement was obtained between experimental data and the Pukanszky model prediction. Scanning electron microscopy studies also revealed better dispersion of silane treated filler particles in the PP matrix.Article Citation - WoS: 30Citation - Scopus: 31Water and Water Vapor Sorption Studies in Polypropylene-Zeolite Composites(Wiley, 2003) Pehlivan, Hilal; Özmıhçı, Filiz; Tıhmınlıoğlu, Funda; Balköse, Devrim; Ülkü, SemraWater and water vapor sorption to porous polypropylene-zeolite composites prepared by hot pressing have been studied as a function of zeolite loading. This work presents the first report on the effect of the zeolite as a filler on the water-sorption properties of PP composites. Water swelling experiments were conducted at 25°C using pure PP and PP-zeolite films samples having different zeolite loadings (6-40 wt %). Because PP is a hydrophobic polymer, it does not sorp any water, but the composites having 10, 20, 30, and 40% zeolites have sorbed 0.63, 1.00, 1.72 and 3.74% water, respectively. The zeolite itself at the same conditions sorbed 24.5% water. As the filler loading in the composites increased, equilibrium uptake values increased also. On the other hand, water vapor sorption and kinetics has been studied using a Cahn 2000 gravimetric sorption system. Within in the range of 0.35-0.95% water vapor was adsorbed by the composites containing 10-40 wt % zeolites. Experimental effective water vapor diffusivities of the composite films was about one order of magnitude higher (10-fold) than the experimental water diffusion coefficient in composites. The transport of water in composites was slower than that in the liquid water due to the longer diffusion pathway and adsorption on the surface of the composites. Although the liquid water may fill all the voids in the composite, water vapor is adsorbed on the surface of the zeolite only.