Elongation induced demonstration of the fraction dependent filler network structures in silicone rubber: An in situ SAXS study

Aiming to unveil the filler network structures in silicone rubber with various filler volume fraction (ΦSi), in situ tensile-small-angle x-ray scattering (SAXS) was conducted on composites with ΦSi of 0%, 11.9%, 18.4%, and 26.5% (S0, S30, S50, and S80). For the static state of S30, S50, and S80, the aggregates sizes decrease from 65 nm, 53 nm–42 nm, while the homogeneity of aggregates and filler network is improved. With the help of in situ SAXS, intrinsic differences of filler networks on vertical (V) and horizontal (H) of the elongation direction related to ΦSi are further unveiled. During elongation, the relative stable peak position in medium-q range of Kratky plots indicate that the aggregates as a stable unit (form factor) of the filler network. In V direction, the almost unchanged intensity of S30 indicates the insignificant changes statistically due to high heterogeneity of filler network. The decreased low-q intensity of S80 indicates the compression of relatively homogeneous filler network. While in H direction, additional peaks appear for all the samples, which are low-q shift with increasing the strain. However, for S30, the peaks mainly come from the separation of the initially adjacent aggregates. For S80, the clear increased low-q intensity suggests the initial existed correlation length is expanded.