Issue
EPL
Volume 88, Number 5, December 2009
Article Number 56001
Number of page(s) 5
Section Condensed Matter: Structural, Mechanical and Thermal Properties
DOI http://dx.doi.org/10.1209/0295-5075/88/56001
Published online 07 December 2009
EPL, 88 (2009) 56001
DOI: 10.1209/0295-5075/88/56001

Anomalous ductility in thermoset/thermoplastic polymer alloys: An explanation based on overlap concentration and cavity growth

Debashish Mukherji and Cameron F. Abrams

Department of Chemical & Biological Engineering, Drexel University - Philadelphia, PA 19104, USA

debashish.mukherji@drexel.edu

received 4 September 2009; accepted in final form 9 November 2009; published December 2009
published online 7 December 2009

Abstract
Using large-scale molecular-dynamics simulations, we investigate the mechanical behavior of thermoset/thermoplastic polymer alloys. We focus here on the effect of linear-chain mass fraction $\Gamma _{l}$, for different chain lengths Nl, and strain rates $\dot{\varepsilon} $. Our results show that tensile strain (i.e., strain to break) decreases with increasing $\Gamma _{l}$ up to a threshold value $\Gamma ^{*}_{l}$, beyond which it increases with $\Gamma _{l}$. This non-monotonic behavior, which we call “anomalous ductility", is qualitatively independent of $\dot{\varepsilon} $ and Nl, so long as fracture occurs in bulk. However, for larger strain rates (i.e., $\dot{\varepsilon} \geqslant 5 \times 10^{-4} \tau^{-1} $) adhesive fracture occurs and no anomalous ductility is observed. $\Gamma ^{*}_{l}$ decreases with increasing Nl and we observe microscopic evidence that $\Gamma ^{*}_{l}$ signifies the onset of interchain interactions. A simple scaling argument suggests that $\Gamma ^{*}_{l}$ is related to the overlap concentration c* of the thermoplastic homopolymer in the cured thermoset matrix.

PACS
61.41.+e - Polymers, elastomers, and plastics.
87.15.La - Mechanical properties.
87.10.Tf - Molecular dynamics simulation.

© EPLA 2009