Thermodynamic Properties of Fluorinated Polymers.

Gregg Caldwell, Siddharth Dasgupta, William A. Goddard III

Materials and Process Simulation Center,

Beckman Institute (139-74),

California Institute of Technology

Pasadena, CA 91125, USA

Abstract:

We have used molecular dynamics to calculate thermodynamic properties a variety of polymers, specifically fluorinated polymers. We are using atomistic simulations to generate equation of state data for various polymers as well as get a better understanding of their bulk and surface properties.

As part of a project to accurately simulate performance of conventional munitions, we are looking at polymers that are used as binders for explosives. The Mie-Grüneisen equation of state has been widely accepted to model solid material behavior at elevated pressures. We have looked at Kel F-800, Estane® and PCTFE and calculated the Grüneisen parameter:

In other polymers, the fluorinated portion of the material is present as a side chain. We are looking at poly(fluoroalkyl acrylate)s (PFAAs) and trying to understand the surface properties of these materials. The surface structure affects the surface properties and the morphology of the bulk material influences the surface structure. In this study we trying to get information on the lowest surface free energy of the materials and correlate to an experimental performance measure, namely contact angles.

Figure 1: Straight chained, amporphous Kel F-800