File(s) under permanent embargo

Autonomous damage initiated healing in a thermo-responsive ionomer

journal contribution
posted on 01.08.2010, 00:00 authored by Russell VarleyRussell Varley, S van der Zwaag
The partially neutralised poly[ethylene-co-(methacrylic acid)] copolymer Surlyn 8940® (DuPont) ionomer exhibits damage-initiated healing during high-energy impact. This is attributed to the hierarchical structure of ionomers, arising from the presence of ionic aggregates and hydrogen bonding. This work investigates the mechanism of this process using novel techniques developed here. The ionomer's response to penetration has been found to consist of three consecutive events: an initial elastic response, an anelastic response and pseudo-brittle failure. In addition, the ultimate level of healing has been shown to be dependent upon the elastic response during impact as well as post-failure viscous flow. Increasing the local temperature at impact consistently increases elastic healing, although further improvements in healing are minor once the local temperature increases beyond the melting point. Below the order-to-disorder transition, microscopic investigations reveal severe plastic deformation while the lack of shape memory reduces the comparative level of elastic healing. Above this temperature, healing is facilitated by elastomeric behaviour at the impact site, while above the melting point a combination of elastomeric and viscous flow dominates. This work provides for the first time evidence of the consecutive healing events occurring during high-impact penetration for ionomers. The hierarchical structure of ionomers and its impact upon the microstructure have been shown to be critical to the process. Comparison of the mechanical response during impact with that of non-ionic polymers further highlights this. In addition, slow relaxational processes occurring post-impact are found to facilitate further recovery in mechanical properties.

History

Journal

Polymer International

Volume

59

Issue

8

Pagination

1031 - 1038

Publisher

John Wiley & Sons

Location

Chichester, Eng.

ISSN

0959-8103

eISSN

1097-0126

Language

eng

Publication classification

C1.1 Refereed article in a scholarly journal

Copyright notice

2010, Society of Chemical Industry