Turning Vulcanized Natural Rubber into a Self-Healing Polymer

Effect of the Disulfide/Polysulfide Ratio

Journal article (2016)

Authors

M. Hernandez Santana Novel Aerospace Materials - Aerospace Engineering
A.M. Grande Novel Aerospace Materials - Aerospace Engineering
W. Dierkes University of Twente
J.C. Bijleveld Novel Aerospace Materials - Aerospace Engineering
Research Group
Novel Aerospace Materials (Aerospace Engineering) (TU Delft)
Self-healing Elastomer Vulcanized natural rubber Degree of curing Disulfides, Polysulfides Time dependence Electron spin resonance
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Published Date

2016

Language

English

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Faculty

Aerospace Engineering

Department

Aerospace Structures & Materials

Research Group

Novel Aerospace Materials

Abstract

A self-healing sulfur vulcanized natural rubber (NR) is here reported using the common ingredients in a traditional NR formulation. The dynamic character of the di- and polysulfide bonds naturally present in covalently cross-linked rubbers was found to be responsible for the healing ability and the full recovery of mechanical properties at moderate temperatures provided the material was employed in a nonfully cured starting state. Results show that a compromise between mechanical performance and healing capability can be reached by tailoring the amount of sulfur, the cross-linking density, and the disulfide/polysulfide ratio. The healing efficiency was found to depend on the postcuring storage time, the time between damage creation and re-establishment of mechanical contact, and the actual healing time. Furthermore, a dedicated electron spin resonance (ESR) test allowed establishing the underlying healing principle based on temperature-induced free sulfur radicals. The main observations presented here can serve as the basis for the design and preparation of other self-healing polymers with long-term durability based on di-/ polysulfide bridges and other reversible moieties