Anomalous ductility in thermoset/thermoplastic polymer alloys

Abstract

Mechanical properties of highly cross-linked polymer (HCP) networks, e.g., thermosets, can be significantly modified by adding linear polymer chains, e.g., thermoplastics. In this work, we study thermoset/thermoplastic polymer alloys by means of large scale molecular dynamics simulations (MD) of a coarse-grained model. We focus here on the effect of the linear chain fraction, Gammal, on the mechanical properties of HCP network for a fixed chain length. Our MD simulations show that the ductility (measured by the strain-to-fracture) of an alloy decreases with increasing Gammal up to a threshold fraction, Gammal*, beyond which it increases with Gammal. We find that for Gammal<Gammal* the fracture is predominantly cohesive, while for Gammal>Gammal* adhesive failure occurs. 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 Gammal increases, and (b) reduction of cross-linker density with increasing Gammal.

Dynamic Study of Deformation and Adhesion of an Amorphous Polyethylene/Graphene Interface: A Simulation Study

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Improving mechanical properties and processability of a very high Tg epoxy amine network via anti‐plasticizer fortification

“…The use of partially reacted substructures (PRS) is an emerging strategy seeking to develop a network topology able to strain harden under tension while not significantly impacting T g . This is supported by molecular dynamics simulations, which predicted that increased ductility arises from a combination of void formation under strain and lower crosslink density of the polymer network 25,26 . The premise is that localized concentrations of noncovalently bound molecular surfaces will induce favorable void growth under strain and hence improved ductility.…”

“…This is supported by molecular dynamics simulations, which predicted that increased ductility arises from a combination of void formation under strain and lower crosslink density of the polymer network. 25,26 The premise is that localized concentrations of noncovalently bound molecular surfaces will induce favorable void growth under strain and hence improved ductility. Sharif and Palmese showed that by pre-reacting a mono-amine and a tetra-functional epoxy resin to 60% and 80% conversion prior to addition to the uncured epoxy resin network, 27 a higher elongation to break was achieved despite a significant reduction in T g .…”

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