Comparative Study of Filler Network Formation and Recovery Kinetics in PVMQ Reinforced With Fumed and Precipitated Silica: Insights From Strain‐Dependent Rheology

In the reinforcing of silicone rubber, fumed silica has consistently outperformed precipitated silica. However, the reinforcement mechanisms remain controversial due to an incomplete understanding of filler network effects and unclear impacts of filler networks on the macroscopic properties of polymer nanocomposites. This study systematically investigates how two distinct filler structures, fumed silica HBT and surface‐modified precipitated silica HT36‐5, influence the Payne effect and network recovery kinetics in PVMQ composites through dynamic strain amplitude sweeps and time‐dependent modulus recovery experiments. By calculating the fractal dimension of the flocs (D f ), it was found that the aggregate structures formed by HBT exhibit a relatively loose packing pattern (D f = 1.85) and are prone to break into smaller floccules under shear forces, leading to improved dispersibility. In contrast, the aggregate structures formed by HT36‐5 display a more compact arrangement (D f = 2.32), resulting in poorer dispersibility. Tensile tests further demonstrate that the interconnected filler network significantly enhances the mechanical strength of vulcanized composites, particularly at high filler loadings (up to 50 phr). This study systematically reveals the regulatory mechanism of filler structure on the properties of composites from three aspects: aggregate structure, network formation, and rheological response, providing new insights for the design of high‐performance elastomers.