In this context, the goal of this work is to study the effect of acetone solvent on the curing process as well as on the properties of epoxy matrices. Thus, acetone/epoxy solutions of different acetone concentrations, namely 0.0, 7.0, 10.0 or 13.0 wt.%, were prepared and then subjected to a mild processing route to remove acetone. Viscosimetric, thermogravimetric, tensile and morphological tests were performed in order to evaluate possible changes in the samples. In addition, Fourier transform infrared spectroscopy (FTIR) analyses were also employed in the search for changes in their molecular structure. Experimental MaterialsThe epoxy resin and the hardener used were araldite GY 251 (diglycidylether of bisphenol A, DGEBA, Huntsmann) and aradur HY 956 (Huntsmann), respectively. Acetone (Quimidrol, 99.5% purity) was the chosen solvent. MethodologyA certain amount of acetone (7.0, 10.0, or 13.0% of the resin weight) was added to the resin and the mixture was simultaneously sonicated in a Sonics Vibration (500 W) and magnetically stirred for an hour. The mixture was then subjected to heating at 50 °C for an hour and conditioned under vacuum for five hours. Finally, hardener was added to the mixture with a 5:1 (w/w) epoxy resin:hardener ratio and homogenized. The curing process took place at room tempera-

The authors employed the equilibrium molecular dynamics technique to calculate the self-diffusion coefficient and the shear viscosity for simple fluids that obey the Lennard-Jones 6-12 potential in order to investigate the validity of the Stokes-Einstein (SE) relation for pure simple fluids. They performed calculations in a broad range of density and temperature in order to test the SE relation. The main goal of this work is to exactly calculate the constant, here denominated by alpha, present in the SE relation. Also, a modified SE relation where a fluid density is raised to a power in the usual expression is compared to the classical expression. According to the authors' simulations slip boundary conditions (alpha=4) can be satisfied in some state points. An intermediate value of alpha=5 was found in some regions of the phase diagram confirming the mode coupling theory. In addition depending on the phase diagram point and the definition of hydrodynamics radius, stick boundary condition (alpha=6) can be reproduced. The authors investigated the role of the hydrodynamic radius in the SE relation using three different definitions. The authors also present calculations for alpha in a hard-sphere system showing that the slip boundary conditions hold at very high density. They discuss possible explanations for their results and the role of the hydrodynamic radius for different definitions in the SE relation.

In this work, nanocomposites were prepared by adding a small amount of single walled carbon nanotubes (SWCNTs) to an epoxy resin aiming to study the resulting mechanical, viscoelastic and thermal properties of the nanocomposites. To optimize the processing of the nanocomposites and to favor a homogeneous dispersion of the SWCNTs on the matrix, acetone was used to reduce resin viscosity, increasing diffusion of the SWCNTs in the solution. The epoxy/SWCNTs/acetone systems were also sonicated in order to minimize entanglement of the SWCNTs. The systems were characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, thermogravimetry, differential scanning calorimetry and dynamic mechanical analysis. The results indicated that the addition of small amounts of SWCNTs to epoxy leads to slight structural changes in the epoxy matrix which, together with the presence of SWCNTs, may reflect on its mechanical and viscoelastic properties

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