Polypropylene/graphene nanoplatelets nanocomposites with high conductivity via solid-state shear mixing

The research on facile, low-cost, and green process for the uniform dispersion of graphene nanoplatelets (GNPs) into polymer matrix has always been a considerable challenge in practical applications. The Van der Waals interaction between graphene layers can easily cause aggregation of the nanofillers. Here, we propose a new method to solve this problem by involving solid-state shear mixing to obtain a well-dispersed nanocomposite. The comprehensive properties of nanocomposite, including antistatic properties, mechanical properties, and thermal stability, can be significantly enhanced by this method. The surface resistivity of the nanocomposite can be up to 2.4 × 107 Ω sq−1 under 1 wt% content of GNPs, which is significantly better than the value obtained by conventional melting compounding and meets the required standard of less than 3 × 108 Ω sq−1 for actual application antistatic materials. The impact strength of the nanocomposite increased by 120.8% when compared with neat PP. At the same time, the heat distortion temperature and initial decomposition temperature of the nanocomposite with only 0.5 wt% content of GNPs are improved by 11.7°C and 110°C, respectively. In addition, GNPs is a heterogeneous nucleating agent that leads PP to emerge β crystal form. This study provides an effective and practical reference for the broad-scale industrial preparation of polymer-based graphene nanocomposites.

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.