Dielectric dynamics of some nylon 6/CaCO3 composites using broadband dielectric spectroscopy

Epoxy resin reinforced with graphene derivatives: physical and dielectric properties

Epoxy resins are important industrial polymers due to their versatile properties and ease of preparation. They are used on a large scale in coating and adhesives applications. Epoxy resins are prepared by photo-curing technique or thermal curing method in presence of different hardeners. The first method is used for small areas while the latter is utilized mainly for coating applications. Graphene and its oxide have proved themselves as good fillers for epoxy resin since the formed composites demonstrated enhanced mechanical, thermal and electrical properties. This article gives insight view for synthesis techniques and properties of these composites with a deep discussion for electrical and dielectric investigations of epoxy resins loaded with threshold concentration of graphene oxide. A case study of dielectric properties of epoxy resin/modified graphene oxide composite, is presented in which effect of curing technique on dielectric behavior is explored. Although the amount of filler was kept at the threshold concentration (1% by weight) obvious change in the dielectric properties could be observed unlike the rest of properties.

Influence of specific intermolecular interactions on the thermal and dielectric properties of bulk polymers: atomistic molecular dynamics simulations of Nylon 6

Specific intermolecular interactions, in particular H-bonding, have a strong influence on the structural, thermal and relaxation characteristics of polymers. We report here the results of molecular dynamics simulations of Nylon 6 which provides an excellent example for the investigation of such an influence. To demonstrate the effect of proper accounting for H-bonding on bulk polymer properties, the AMBER99sb force field is used with two different parametrization approaches leading to two different sets of partial atomic charges. The simulations allowed the study of the thermal and dielectric properties in a wide range of temperatures and cooling rates. The feasibility of the use of the three methods for the estimation of the glass transition temperature not only from the temperature dependence of structural characteristics such as density, but also by using the electrostatic energy and dielectric constant is demonstrated. The values of glass transition temperatures obtained at different cooling rates are practically the same for the three methods. By proper accounting for partial charges in the simulations, a reasonable agreement between the results of our simulations and experimental data for the density, thermal expansion coefficient, static dielectric constant and activation energy of γ and β relaxations is obtained demonstrating the validity of the modeling approach reported.