Anomalous Ductility in Thermoset/Thermoplastic Polymer Alloys

Mechanical properties of highly cross-linked polymer (HCP) networks, e.g., thermosets, can be significantly modified by adding linear polymer chains, e.g., thermoplastics.

We use large scale molecular dynamics simulations (MD) of a coarse-grained model to study thermoset/thermoplastic polymer alloys. We focus here on the effects of linear chain fraction,

linear chain length and strain rate. Our MD simulations show that the ductility (measured by the strain-to-fracture)

of an alloy decreases with increasing linear chain fraction up to a threshold value, beyond which it increases with

linear chain fraction. This anomalous behavior in ductility is independent of strain rate and linear chain length.

We suggest that the possible origin of this unexpected non-monotonic behavior is due to a competition

between (a) growth of microvoids which stores mechanical energy and is compromised as linear chain fraction increases,

and (b) reduction of cross-linker density with increasing linear chain fraction.