jrups
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Abstract: The Polyamide 6 (PA6) / Polyvinyl alcohol (PVOH) blends of different compositions (80/20, 60/40 and 50/50) were prepared by melt mixing in a Haake Rheomixer. The selected blend systems (80/20 and 60/40) were modified with dicumyl peroxide (DCP) and tertiary butyl cumyl peroxide (TBCP). The dynamic mechanical properties of blends were systematically investigated with special reference to the effect of blend ratio and effect of presence of peroxide over a temperature range -20°C to 110°C. The effect of change in the composition of the polymer blends on tan δ was studied to understand the damping characteristics. The mean field theory developed by Kerner has been used to estimate the dynamic properties and the estimated values are compared with the experimental values. The loss tangent curve of the blend exhibited single transition peak corresponding to the glass transition temperature (Tg) of Polyamide 6. Kerner model was found to satisfactorily predict the viscoelastic properties of the blends with polyamide content in the range 50 to 80 wt% assuming PA6 as matrix and for all compositions except 80/20 assuming PVOH as matrix. The Kerner model predictions for the selected blend systems with peroxides are not satisfactory and the co-continuous morphology of the peroxide treated blends were revealed by SEM observations. Keywords: Polymer blends, Dynamic mechanical analysis, Kerner model, Morphology, peroxide modified blends. |
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Abstract: With the aim of obtaining giant polymer vesicles supporting a hindered amine that is converted into a redox catalyst on the vesicle shells, the living nature of the photo nitroxide-mediated living radical polymerization (photo NMP) of a monomer containing a hindered amine and the formation of the vesicles consisting of an amphiphilic diblock copolymer by the polymerization-induced self-assembly were investigated. The photo NMP of 2,2,6,6-tetramethyl-4-piperidyl methacrylate (TPMA) was performed in methanol using 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (MTEMPO) as the mediator, 2,2’-azobis[2-(2-imidazolin-2-yl)propane] (V-61) as the initiator, and (4-tert-butylphenyl)diphenylsulfonium triflate as the accelerator by UV irradiation at room temperature. The first-order time-conversion plots had an induction period in which the MTEMPO molecules were captured by the initiator radicals and the monomer radicals generated by the initiation. It was confirmed that the polymerization proceeded by a living mechanism based on linear correlations of the molecular weight of the poly(TPMA) (PTPMA) versus the monomer conversion and the reciprocal of the initial concentration of V-61. Based on the livingness of the polymerization, the photo NMP-induced self-assembly for the block copolymerization of methyl methacrylate (MMA) using the PTPMA end-capped with MTEMPO was carried out in methanol to produce microsized giant spherical vesicles consisting of the amphiphilic PTPMA-block-poly(MMA) diblock copolymer. A differential scanning calorimetry study demonstrated that the vesicles had a single bilayer structure. Keywords: 2,2,6,6-Tetramethyl-4-piperidyl methacrylate (TPMA), Hindered amine, Photo nitroxide-mediated living radical polymerization (photo NMP), Photo NMP-induced self-assembly, Giant vesicles, Single bilayer structure. |
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Abstract: Biodegradable polymers are important as an alternative to conventional non-degradable polymers for sustainable eco-system. The recent trends indicate that the new developments in biodegradable polymers focus on novel polymer systems that can cater the need of biomedical and packaging applications in-terms of performance and economics. The new interest is rapidly moving toward reducing carbon footprint through utilization of carbon dioxide and developing new methods of manufacturing such as 3D printing for specific purposes. This review focus on the present state-of-art and recent developments in biodegradable polymers covering their sources, synthetic methodologies, salient properties, degradation patterns, polymer blends and nanocomposites. As well as biodegradable polymers as a 3D printing material and the use of carbon dioxide as a renewable raw material for biomedical and packaging applications. Keywords: Biodegradable polymers, polymer blends, 3D printing, carbon dioxide, renewable resources. |
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Abstract: The article highlights some recent trends in the bleaching of textile materials. An attempt has been made to compare the effect of electrochemical bleaching with conventional bleaching of cotton. Electric current is used in the preparation of a bleaching agent to replace bleaching powder. The sodium hypochlorite generated from electrolyte cell is sufficient to produce powerful bleaching agent with available chlorine. Electrochemical bleaching with sodium hypochlorite offers numerous advantages like prevention of effluent problem, economy, reliability, cleanliness, and convenience in working. Attempts have been made to use sodium perborate as a bleaching agent with potassium persulphate as an activator at lower temperature in combined pre treatment of cotton fabric. Experimental trials have been designed by using taguchi technique. This bleaching technique promises to be eco-friendly process. In yet another interesting work, effort has been taken to bleach the scoured cotton fabric with sodium perborate as bleaching agent and tetreacetyl ethylenediamine as bleaching activator. The concentrations of these chemicals, temperature and time of the treatment have been varied. The utilization of hydrogen peroxide is much higher as compared with that of conventional bleaching process. Other advantages include less requirement of water and energy, thereby satisfying needs of eco-friendly process, lesser loss in weight, tearing strength, and tensile strength, in comparison with conventional bleaching process without compromising whiteness index. Keywords: Sodium hypochlorite, Electrochemical bleaching, tetreacetyl ethylenediamine, Whiteness index, Cotton fabric, Combined pretreatment. |
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Abstract: Standalone composite films were prepared using modified polyester as a binder and waste iron oxides (mill scales) collected from a steel plant as inorganic filler. The morphology, structure, composition, strength and electrical insulation properties of polymer-iron composites were studied using various analytical techniques such as X-ray diffraction (XRD), Scanning electron microscope (SEM), Atomic force microscopy (AFM), optical microscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray fluorescence (XRF), Brunauer–Emmett–Teller (BET) test, particle size analysis and electrical insulation test. The mill scales collected from the hot strip rolling mill (HSM) have found to comprise three different phases such as wustite, magnetite and hematite. Composites prepared using mill scales were showing three times higher strength compared to the mother polymer film. Electrical insulation of these composites were found to increase in the range of 55-230 MV/mm with increasing iron oxide content from 0.0125 g to 0.25 g in 2.5 g polymer. These results show a potential research field on the mill scales based composites for various advanced applications in improving insulation behaviour of materials which can withstand at higher temperatures and electrical stresses. Keywords: Mill scales, composites, iron oxides, electrical insulation, hardness, polymer film. |