(123b) Simulation Studies of the Effect of Reactant Molecular Architecture On the Mechanical Properties of Thermosetting Polymers

Simulation Studies of the Effect of Reactant Molecular Architecture on the Mechanical Properties of Thermosetting Polymers

Modifying the properties of thermosetting polymers used in composite systems by manipulating the chemistry and molecular architecture of resin components is of considerable interest in advanced engineering applications. Thus for example, there is a need to understand how chemistry and thermoset topology affect fundamental material properties such as small strain elastic behavior, material toughness, thermal and electrical properties, and aspects of behaviour such as adhesion and the tendency to undergo microcrack formation under conditions of temperature cycling and exposure to wet or humid environments.

In recent simulation work on polymer blends containing polystyrene and poly(2,6-dimethyl-1,4-phenylene oxide), it was shown that atomistic simulation using accurate force fields can be used effectively to predict relatively small changes in tensile moduli of the material as a function of blend composition when the results are analyzed using the Hill-Walpole bounds analysis approach applied to polymers by Suter and Eichinger [1-4]. The present work accordingly extends the earlier investigation by applying the approach to models of thermoset polymers used as composite matrix material.

After briefly summarizing the earlier studies [4], we present a description of the thermoset building approach and examine its ability to create defect-free densely crosslinked systems with high degree of conversion. This is followed by a study of epoxy thermosets in which the effect of varying reactant architecture using resins with chemical functionalities of 2, 3 and 4 (so-called RA₄+R'B₂, RA₄+R'B₃ and RA₄+R'B₄ polymerization types) is studied by calculating elastic constants and analyzing using the Hill-Walpole approach. The presentation will conclude with a discussion of results from ongoing studies of mechanical properties in which the epoxy-based materials are replaced by higher performance polyimide-based resin.

References:

1. Hill, R. J. Mech. Phys. Solids 13, 213 (1965).
2. Walpole, L.J. J. Mech. Phys. Solids 14, 151 (1966).
3. Suter, U.W. and Eichinger, B.E., Polymer 43, 575 (2002).
4. Rigby, D., Saxe, P.W. and Freeman, C.M., 2012 AIChE Annual Meeting, Pittsburgh, PA.; manuscript in preparation.