Search results for "Epoxy"
showing 10 items of 384 documents
Incorporation of Silica Nanospherical Particles in Epoxy–Amine Crosslinked Materials II. Dynamic Mechanical Measurements of Epoxy Matrix-Silica Nanoc…
2009
The mechanical strengths of epoxy composites reinforced with silica nanospheres, unfunctionalised or functionalised with either amine or epoxy groups, increase up to a proportion of 5 wt.% of filler, as reflected in a study of the shear storage modulus carried out in dynamic mechanical analysis. This improvement is observed in both glassy and rubbery states, moderately affecting the glass transition temperature of the material. From this percentage of strengthening substance the mechanical properties begin to deteriorate, but keeping (up to 10 wt.% of strengthening material), a greater storage modulus in shear than that of the pristine epoxy resin. A trend can be discerned as the percentag…
Dynamic Mechanical Measurements of Epoxy Matrix-Silica Nanocomposites II
2009
The mechanical properties of epoxy-silica nanocomposites have been studied; the silica nanosphere fillers used were un-functionalised, functionalised with amine, with epoxy, or a mixture of both kinds. Dynamic mechanical analysis measurements revealed an increase in the shear storage modulus, for all samples with a filler content of 3–5%. Improvements were observed in the glassy and rubbery states, without affecting the glass transition temperature of the materials. Above these strengthening percentages, the mechanical properties began to deteriorate, but in all cases they remained superior to those of the pristine epoxy resin. For low strengthening percentages, samples reinforced with bot…
Morphology, flexural, and thermal properties of sepiolite modified epoxy resins with different curing agents
2006
A bisphenol A-based epoxy resin was modified with 5 wt% organically modified sepiolite (Pangel B40) and thermally cured using two different curing agents: an aliphatic diamine (Jeffamine D230, D230) and a cycloaliphatic diamine (3DCM). The morphology of the cured materials was established by scanning and transmission electron microscopy analysis. The thermal stability, thermo-mechanical properties, and flexural behaviour of the sepiolite-modified matrices were evaluated and compared with the corresponding neat matrix. The initial thermal decomposition temperature did not change with the addition of sepiolite. The flexural modulus of the epoxy matrix slightly increases by the incorporation o…
Modeling of creep for multiwall carbon nanotube/epoxy nanocomposite
2013
The effect of multiwall carbon nanotubes (MWCNTs) on creep of epoxy matrix was evaluated on the basis of short-term creep-recovery tests performed at different stresses and temperatures. Six different compositions of MWCNT and bisphenol A epoxy resin (0-3.8 wt % of MWCNTs) were investigated. Slight reduction of creep compliance, strain rate, and residual strain were revealed experimentally for nanocomposite comparing to the neat resin. The development of viscoelastic strain for creep stage was described by the use of time-temperature-strain superposition principle with the parameters obtained from the approximation of recovery stage using modified Schapery model. The model accounted for the…
Quantitative optical analysis of filler dispersion degree in MWCNT-epoxy nanocomposite
2012
Recently developed methodology of quantitative analysis based on optical analysis of filler particles' area distributions is applied now to estimate the dispersion efficiency of multiwall carbon nanotubes in nanocomposite prepared by solution intercalation method. Experimental parameters of dispersing (temperature, duration and power level of ultrasonication) were optimized and the most effective experimental procedure was determined. The methodology of determination of dispersion parameter is proved by indirect method of light transmittance experiments. The nanocomposite specimens having lower dispersion parameter represented the highest transmittance over the nanocomposite specimens. 2011…
Moisture effect on deformability of epoxy/montmorillonite nanocomposite
2010
In this article the moisture effect on deformability of epoxy/montmorillonite nanocomposite was investigated. The change of fracture character and drop of elastic characteristics due to moisture absorption was observed. The estimation of filler morphological peculiarities (platelet stack constitution) in composite and its effect on nanocomposite elastic properties was undertaken. It is shown that the higher number of filler platelet per stack consistently leads to the decrease of nanocomposite elastic properties. Nevertheless prediction by micromechanical model is rough for moistened nanocomposite because of resin structural changes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
DIELECTRIC PROPERTIES OF EPOXY RESIN COMPOSITES FILLED WITH NANOCARBON INCLUSIONS
2013
The epoxy resin composites with various carbon additives were investigated in the frequency range of 20 Hz - 3 GHz at temperatures from room to 500 K. The dielectric properties were found to be strongly impacted by percolation threshold. The lowest percolation threshold (< 0.25 wt.%), was observed in composites with single-walled carbon nanotubes.
Water transport in epoxy/MWCNT composites
2013
Moisture and water uptake of epoxy/multi-wall carbon nanotube (MWCNT) composites was studied in a wide range of atmosphere relative humidity and temperatures. Addition of up to 1 wt.% of MWCNTs into the neat epoxy resulted to the twofold decrease of the diffusivity, while the levels of moisture/water uptake remained unchanged. The positive effect on the reduction of the diffusion coefficient diminishes with the increase of temperature. Differences in the water transport properties and plasticization ability of the neat polymer and its nanocomposites are explained by the free volume considerations and the polymer–water interactions, which are verified by the results of thermomechanical analy…
Supravital Uptake of Cationic Dyes by Mast Cell Granules: A Light and Electron Microscope Study
1994
Methylene blue and neutral red were selected for staining mast cell granules by supravital injections. A new technique was applied for embedding in paraffin and Araldite without dislocation or loss of dye. Stabilization and electron microscopic identification of the dyes were achieved by transforming them into electron-dense precipitates using phosphomolybdic acid dissolved in a paraformaldehyde-glutaraldehyde mixture to preserve the ultrastructure of the tissues. It was found that in general the intensity of the light microscopic staining correlated directly with the electron density. Closer study revealed that not all cytoplasmic granules exhibited the same strong affinity for the cationi…
Sporogen, S14-95, and S-curvularin, three inhibitors of human inducible nitric-oxide synthase expression isolated from fungi.
2003
The induction of human inducible nitric-oxide synthase (iNOS) expression depends (among other factors) on activation of the signal transducer and activator of transcription 1 (STAT1) pathway. Therefore, the STAT1 pathway may be an appropriate target for the development of inhibitors of iNOS expression. HeLa S3 cells transiently transfected with a gamma-activated site (GAS)/interferon-stimulated response element-driven reporter gene construct were used as the primary screening system. Using this system, three novel inhibitors of interferon-gamma-dependent gene expression, namely, sporogen, S14-95, and S-curvularin, were isolated from different Penicillium species. These three compounds also …