Structural origin of fast yielding-strain hardening transition in fluoroelastomer F2314

•Mechanical response of fluoroelastomer F2314 shows fast transition from yielding to strain hardening.•Unusual yielding results from destruction of CTFE-domains.•Fast strain hardening is related to formation of fibril crystal.•Destruction of CTFE-domains and formation of fibril crystal is origin of mechanical response.

The mechanical response of fluoroelastomer F2314 under uniaxial extension and its relation with strain-induced structural change are investigated by mechanical analysis, in-situ small angle X-ray scattering (SAXS) and wide angle X-ray scattering (WAXS). Yielding of samples followed by strain hardening is found without necking. Meanwhile, the strain range of strain softening is short, which is 0.77 at 25 °C and 0.3 at 60 °C. Microscopically, solution-cast F2314 shows microphase separation and low crystallinity. Results of WAXS and SAXS indicate strain-induced formation of fibrillar crystal during strain hardening. Based on these findings, it is supposed that the fast relay between destruction of microphase separated domains and formation of fibrillar crystal is the origin of the unique mechanical response.

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