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Abstract: The flexural failure modes and flexural strength of unidirectional carbon fiber/epoxy (CF/epoxy) composites was theoretically analyzed and calculated. The hypothesis that the maximal flexural strength of unidirectional CF/epoxy composites occurred in outer sheet layer was brought forward. Load-displacement curve of unidirectional CF/epoxy composites also demonstrates that it is correct, which is consistent with the assume. Unidirectional CF/epoxy composites were fabricated with winding and compression molding, and three different kinds of fiber packing modes were proposed and the effects of these modes on flexural prosperities of composites had also been analyzed respectively. Three failure modes, namely fracture of fiber, fracture of epoxy resin and interfacial delamination between fiber and matrix, were analyzed by scanning electron microscopy (SEM). The load-displacement curve of unidirectional CF/epoxy composites indicates the plastic deformation is increased with increasing phenolic resin. Keywords: Bending strength, carbon fiber, packing modes, failure mode, composite.Download Full Article |
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Abstract: Biodegradable Hydroxyl propyl Methyl cellulose based polymer composites of various concentrations were prepared by doping carbon particles of kerosene soot. These composites were synthesized by employing simple solution casting method, to study the physical properties of the same. The analytical studies like XRD, AC conductivity, Tensile strength, Acoustic impedance, AFM and FTIR spectroscopy were carried out to characterize these composites. From the results it is seen that, the amorphous carbon particle disturbs the semi crystalline nature of the polymer by getting interstitial into polymer network. Further, this results in the characteristic changes of other physical parameters like tensile strength and AC conductivity. We have made an attempt to establish a structure property relation of such changes in the physical properties with that of microstructural parameters derived from XRD. Keywords: HPMC, Carbon Soot, XRD, Crystallite Size.Download Full Article |
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Abstract: In this work we propose the use of a hydro-dispersible polymer such as the poly vinyl acetate as a binder for the production of electrodes for lithium-ion batteries. To increase the film forming properties of the polymer the poly vinyl was added with triacetin that acts as a plasticizer. The electrochemical stability of the polymer was tested by a polarizing electrode, formed by mixing the polymer with carbon. Subsequently, an electrode tape was prepared by using LiNi0.5Mn1.5O4 as the active material and characterized by SEM, EDS and TGA. Lithium metal cells were assembled and tested to evaluate specific capacity, power and energy density at various discharge rates. The cycle life of the cell was evaluated by galvanostatic charge/discharge cycles. The tests showed that the electrodes prepared with PVA plasticized with triacetin have very good electrochemical performance in terms of capacity retention as a function of the discharge rate and the cycle number. Our work demonstrates that the use of triacetin to plasticize the PVA allows to increase the electrochemical stability of the electrode likely due to an improvement of the slurry filmability. The proposed method could represent a promising technology for the production of long-term performance lithium batteries.. Keywords: Radical polymerization, Polystyrene-b-Poly(4-vinylpyridine), Inverse Gas Chromatography, Specific interactions, Acid and Base Constants. |
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Abstract: Polyaniline (PANI) has been prepared by chemical oxidation method at room temperature and the effect of concentration of dopant Glacial Acetic Acid (CH3COOH) on the structure of the polymer was investigated. Polymers prepared in absence and in the presence of varying concentrations of CH3COOH were characterized using UV-visible, FTIR spectroscopy and conductivity measurements. In UV-visible spectra of PANIs recorded in DMSO revealed that absorption bands increases with increasing concentration of CH3COOH. The FTIR spectra shows the absorption bands related to quinoid and benzenoid rings for the undoped and doped PANI in CH3COOH indicating that the polymer is composed of amine and imine units. Highest conductivity value was obtained in presence of 1.0 M CH3COOH indicating that the more preferable doping of PANI will be at this concentration of CH3COOH. The effect of the temperature upon the conductivity of PANI synthesized with different concentrations of CH3COOH has been studied. Keywords: Doped PANI, CH3COOH, FTIR, UV-visible, Conductivity.Download Full Article |
Abstract : The Solid State 13C NMR Study of Gamma Radiation of Ethylene-Octene Copolymer
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Abstract: Ethylene-octene copolymer (POE) samples exposed to γ-radiation under a series of absorbed doses have been investigated using thermal analysis, sol–gel analysis and solid state 13C nuclear magneticResonance (NMR). The chemical shift of POE was assigned and peak evolution as a function of radiation dose was discussed. An obviously evolution is that the peak area of 33.6 ppm decreases as a function of the increase of radiation dose, and at the same time, the peak shape broadens gradually. This indicates that the chain scission occurred between α-C and branch chain C (methine) or between C1 (the sidegroup hexyl) and branch chain C (methane) after radiation. The chain scission is severer with the increase of absorbed dose.The 13C NMR spectra of the corresponding gels confirmed the result. The variation in linewidth of the resonance at 33.6 ppm in samples of POE irradiated to different doses was attributed to information of chain, scission, new cross linking, and crystalline components. Keywords: Ethylene-octene copolymer (POE), γ-radiation, solid-state 13C NMR, Chain Scission. Download Full Article |