(451e) Tuning the Thermal and Volumetric Properties of Epoxy Nanocomposites: A Molecular Simulation Study

The superior mechanical properties of thermosetting epoxy have led to its widespread usage in the areas of aerospace, electronics and coatings. The curing process of the epoxy leads to the development of residual thermal stresses in the matrix which presents a problem in these applications. A potential strategy for alleviating these thermal stresses consists of incorporation of nanofiller particles in the epoxy matrix. The properties of such nanocomposites formed by the incorporation of nanofiller molecules in the epoxy matrix are governed by the molecular interactions between the nanofillers and the epoxy. Molecular simulations provide the ability for systematically accounting for these detailed atomistic interactions in the system.

Owing to the complex molecular topology of the crosslinked epoxy matrix, the creation of a well relaxed atomistic model structure of crosslinked epoxy at a realistic density is a challenging task. In previous work, we developed an efficient method for generating atomistic model structures of highly crosslinked epoxy. The method involves a single step polymerization of the physical mixture of the epoxy monomers, the crosslinker molecules and the nanofiller particles in the simulation box. The approach was used for generating model structures of neat crosslinked epoxy as well as epoxy-POSS (polyhedral oligomeric silsesquioxane) nanocomposite.

In this work, the modeling approach is extended for studying the nanocomposites formed by the incorporation of different types of nanofiller particles in the epoxy matrix. Specifically, carbon nanotubes as well as POSS particles with differing chemistries (as obtained by varying the chemical functional groups that are attached to the central POSS cage) are chemically incorporated in the crosslinked epoxy matrix. Molecular dynamics simulations are used to characterize the nanocomposite structures thus formed with respect to their density, glass transition temperature and the coefficient of volume thermal expansion. Simulation results are used to determine the ability of these nanofiller particles for tuning the thermal and volumetric properties of epoxy nanocomposites.