jrups
Abstract : Application of Disordered Organic Semiconductor Theory to Low Temperature Curing of Epoxy Resins (3)
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Abstract: The steep autocatalytic feature in a highly accurate DSC study of the heat rate from curing an epoxy resin with piperidine at 27.5 Deg C could not be explained using chemical kinetic power laws usually applied to curing epoxy resin products at higher temperatures. The theory of disordered conjugated organic semiconductors developed in the last decade has been applied to the observed heat rate data. Four heat rate sources have been identified to completely account for the experimental data. Two of the four sources generating 80% of the heat are consistent with mobility change of ion pairs indicating that the low temperature cure follows an organic semiconductor mechanism. It was shown that autocatalysis did not begin until about one fiftieth of the epoxy rings were opened (ignition). After ignition the heat rates of two propagation mechanisms grow exponentially. One charge transport mechanism generates a small heat rate but grows immediately after ignition due to an increase in ion pairs by the dopant (piperidine). The second mechanism appears later but becomes dominant, peaking at 50% completion, where the heat rate is about 50 times higher than the start of the first mechanism. The rate increase is attributed to localized energy sites that lower the LUMO level closer to the HOMO level of the monomer increasing the mobility (heat rate). Keywords: Epoxy resins, kinetics (polym), calorimetry, diffusion, organic semiconductors.Download Full Article |
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Abstract: Spontaneous assembly of nanoparticles onto a surface is a promising bottom-up concept for the fabrication of new functional materials that can be used for various applications in the nanotechnology. In this paper, we describe a system based on gold/polystyrene (Au/PS) Janus particles arranged onto Au self-assembled monolayer (SAM) of 1-dodecanthiol (NDA). The micro-size Au/PS Janus particles are self-assembled onto Au surface and are dissolved into polystyrene (PS) nanoparticles. The SAM of NDA plays two different roles; it dissolves the original Au/PS Janus particles and organizes the PS nanoparticles onto the Au surface. Overall, our proposed method for the assembly of large-scale area nanoparticles can be extended for further uses in the surface science. Keywords: Self-assembled monolayer, Polymeric nanoparticles, Spontaneous arrangement, Polystyrene, Surface chemistry, Janus particles.Download Full Article |
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Abstract: Specific answers are required for purpose of better communication with many researchers, manufacturers, and users of polymer worldwide. This paper posted so many questions about the research activities on bio-based/ renewable thermoset polymers as against petrochemical based thermoset polymers. Quite a few answers were given but the remaining unanswered questions will surely be required in order to better understand the results achieved in this research area. Keywords: Renewable, cost-effective, synthesis, environmentally friendly.Download Full Article |
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Abstract: The report has a double character: it deals with the synthesis and preparation of a series of polymers based on bisphenol-A (BPA) monomer; a series of physical and thermomechanical properties are examined for one type (diglycidyl ether of BPA, DGEBA with nanosilica) of the prepared materials. The reactions involved in diepoxy curing with a diamine, functional group modelling for cross-linked polymers, formation of a polymer DGEBA, BPA polyaddition to DGEBA forming a polyether, DGEBA curing with Jeffamine and cross-linking to form a resin are analyzed. Nanocomposites of silica, coated with cross-linked epoxy–amine, are synthesized and examined by 29Si-magic-angle-spinning nuclear magnetic resonance and Fourier-transform infrared spectroscopies, thermogravimetric and dynamic mechanical analyses, differential scanning calorimetry and scanning electron microscopy. Epoxy matrix is filled with nanosilica to design materials with defined properties. A low weight percentage of filler results in matrix improvement. Keywords: Polycarbonate, polymer, nanocomposite, nanosphere, nanosilica, amine, nanostructure, nanomaterial.Download Full Article |
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Abstract: In this article, a microemulsion method for preparation of magnetite composite polymer nanoparticles of Fe3O4@poly(styrene-methacrylic acid) (MNP@PSMA) crosslinked with1,6-hexanediol diacrylate (HDD) insitu with carboxyl functionality on the surface has been reported. Structure and morphology of the nanoparticles was studied by Fourier Transform Infrared spctroscopy (FTIR), X ray Diffraction (XRD), Thermal Gravimetric Analyser (TGA), Vibrating Sample Magnetometer (VSM) and Transmission Electron Microscopy (TEM). VSM studies confirmed saturation magnetization of 20.0 emu/g in an external magnetic field. Nanoparticles formed were of 30 nm in diameter with narrow size distribution and mosaic structure providing a large surface area useful for application in bioseparation. Experimental results of covalent coupling of composite nanoparticles indicated maximum protein binding capacity of 350 mg bovine serum albumin (BSA) per gram. Keywords: Microemulsion, magnetic nanoparticle supports, protein separation.Download Full Article |