Remarkable enhancement of thermal stability of epoxy resin through the incorporation of mesoporous silica micro-filler (original) (raw)
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An epoxy-silica hybrid was produced from a mixture of an amine-silane functionalized bisphenol-A resin and a siloxane precursor derived from tetraethoxysilane with small amounts of glycidoxypropyltrimethoxysilane coupling agent. The low temperature curing characteristics and final properties of the hybrid system were compared to those of two epoxy controls. Examinations were carried out by differential scanning calorimetry, dynamic mechanical analysis, electron microscopy, thermogravimetric analysis, UV-Vis spectroscopy, SAXS and densitometry. The modulus, strength and ductility were measured in 3-point bending mode at 23 and 50°C.
Polimeros-ciencia E Tecnologia, 2013
In this study, epoxy nanocomposites containing different fractions of n-phenylaminopropyl (POSS) were prepared. The nanocomposites were studied by transmission electron microscopy (TEM), gel content, dynamicmechanical analysis (DMA) and thermogravimetric analysis (TGA). The parameters for Avrami's equation were calculated from the degradation curves. The dispersions used to form the nanocomposites were effective above 5 wt % of POSS, and the gel content increased with the addition of POSS. The DMA analysis exhibited an increase in the storage modulus (E') and a shifting of T g to higher temperatures upon POSS incorporation. The weight loss indicated that the POSS promoted an increase in thermal stability of the epoxy resin. The Avrami parameters demonstrated that the addition of POSS decreased the Avrami constant (k'), increased the half-life (t 1/2) of degradation and promoted changes in the Avrami exponent (n). These results suggest that the increase in the glass transition temperature and thermal stability depend on the reactive groups in the POSS nanoparticles.
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Silica nanoparticles having different sizes were obtained by the sol-gel process and characterized. The prepared nanoparticles were subsequently used as reinforcing fillers to prepare epoxy-based composites with a silica content ranging from 1 to 5 wt %. SEM analysis and tensile tests carried out on the silica-epoxy nanocomposites indicated the absence of particle aggregation and a reinforcing effect in terms of increased elastic modulus. Mechanical properties were also modeled by using a finite element code able to construct a numerical model from a microstructural image of the material. A more reliable model was prepared by considering the presence of an interphase layer surrounding the particles with intermediate elastic properties between the epoxy and the inclusions and a characteristic size proportional to the particle radius. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2382–2386, 2005
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Book of abstracts, 2015
Composites based on an epoxy resin, diglycidyl ether of bisphenol A and SiO 2 nanoparticles, unmodified and surface-modified with a coupling agent 3-glycidyloxypropyltrimethoxysilane, were prepared. Successful modification of the nanoparticles was confirmed by infrared spectroscopy and combined differential scanning calorimetry and thermogravimetric analysis (DSC-TG). Composite materials were prepared by adding 0.5-5 phr (parts per hundred parts of resin) of modified and unmodified nanoparticles into the epoxy resin which was then cured with a poly(oxypropylene) diamine. Curing was followed by DSC, and cured materials were characterised by tensile and hardness testing. Morphology of fractured surfaces after tensile testing was investigated by scanning electron microscopy (SEM). Thermal stability of cured materials was studied by TG and their glass transition temperature determined by DSC. The presence of the filler was found not to influence the curing mechanism of the epoxy resin nor the degradation mechanism of the crosslinked epoxy-amine matrix. Glass transition exhibits a small shift to higher temperatures in composites, which also exhibit increased char formation-at lower filler content for the composite with unmodified nanoparticles and at higher for the one with modified nanoparticles. All composites show improved mechanical properties in comparison with the neat epoxy. For the unmodified particles, strength and modulus are particularly improved at lower nanofiller content due to their better dispersion, as observed by SEM. The modified nanoparticles contributed to a significant increase in elongation at break, increasing the toughness of the cured resin while retaining its strength and without having an adverse influence on the modulus.
Thermo-mechanical and Light Transmittance of Silica Diffusant Filled Epoxy Composites
Epoxy ternary blends (DCN) were prepared by mixing diglycidyl ether bisphenol A (DGEBA), cycloaliphatic epoxy, and novolac epoxy. The silica diffusants were prepared by the addition of spherical silica (SS) into epoxy blends. The thermal properties of the epoxy composites were characterised using a thermo-mechanical analyser (TMA), a differential scanning calorimeter (DSC), and a dynamic mechanical analyser (DMA). It was found that the storage modulus of the epoxy was increased in the presence of SS diffusants. However, the coefficient of thermal expansion (CTE) and the glass transition temperature (Tg) of the epoxy ternary blends was reduced by the addition of SS diffusants, which was because the expansion of the epoxy matrix was constrained in the presence of silica fillers. The UV/Vis spectroscopy results demonstrated that the percentage of transmittance of epoxy was decreased by the incorporation of the silica diffusant.
Effect of nanosilica on the kinetics of cure reaction and thermal degradation of epoxy resin
Chinese Journal of Polymer Science, 2011
Nanocomposites from nanoscale silica particles (NS), diglycidylether of bisphenol-A based epoxy (DGEBA), and 3,5-diamino-N-(4-(quinolin-8-yloxy) phenyl) benzamide (DQPB) as curing agent were obtained from direct blending of these materials. The effect of nanosilica (NS) particles as catalyst on the cure reaction of DGEBA/DQPB system was studied by using non-isothermal DSC technique. The activation energy (E a ) was obtained by using Kissinger and Ozawa equations. The E a value of curing of DGEBA/DQPB/10% NS system showed a decrease of about 10 kJ/mol indicating the catalytic effect of NS particles on the cure reaction. The E a values of thermal degradation of the cured samples of both systems were 148 kJ/mol and 160 kJ/mol, respectively. The addition of 10% of NS to the curing mixture did not have much effect on the initial decomposition temperature (T i ) but increased the char residues from 20% to 28% at 650°C.