title: 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.
authors.affiliation: Department of Chemical & Biological Engineering, Drexel University, Philadelphia, PA 19104, USA. debashish.mukherji@drexel.edu
authors.forename: Debashish
authors.initials: D
authors.lastname: Mukherji
authors.forename: Cameron F
authors.initials: CF
authors.lastname: Abrams