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The hierarchical structures of silica-filled silicone rubber have been investigated by using contrast variation small-angle neutron scattering (CV-SANS) and transmission electron microscopy (TEM). A series of scattering intensities of swollen samples were measured with varying ratio of hydrogenated toluene/deuterated toluene solvent. By using CV-SANS method, the partial scattering functions, self-terms of silica S SS ( q ) and silicone rubber S RR ( q ), as well as cross-term between silica and silicone rubber S RS ( q ), are successfully extracted. The fine parameterization of morphology is characterized and elucidated by adopting unified Guinier-exponential/power-law equations, the fitted results indicate: (i) the volume fraction of silicone rubber in bound rubber and matrix regions, are respectively 0.80 and 0.31. Such spatial inhomogeneous of swelling ratio suggests that there is existence of the immobilized layer; (ii) the average aggregation size is ca . 143 nm, and there are about 24–97 silica particles in each aggregation; (iii) the thickness of the bound rubber is estimated as in the range of ca . 7.2–8.5 nm. A mimic collection and observation of aggregations and bound rubber with TEM confirm the CV-SANS results. Current work provided a scenario to evaluate the reinforcement effect of the silica on the silicone rubber even before any mechanical testing.

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.