Swelling Kinetics and Thermodynamic Behavior of Silica Ash–Filled Silicone Rubber in Mixed Aromatic–Aliphatic Solvents: A Two‑Way ANOVA Study

Abstract Silicone rubber (PDMS) is elastic and biocompatible but swells excessively in organic solvents, limiting its use in harsh environments. This study assesses industrial silica ash as a sustainable filler to improve solvent resistance, especially in mixed aromatic-aliphatic environments. Composites with 0, 15, and 30 weight percent silica ash were tested in toluene, kerosene, and their mixtures. Swelling decreased by 30 to 50 percent, with equilibrium uptake in toluene dropping from 145.8 percent (no filler) to 72.3 percent at 30 percent filler. The polymer volume fraction (Vr) in toluene increased from 0.352 to 0.509, and crosslink density (ν e ) rose from 0.0006 to 0.0018 mol/cm³. Transport analysis showed a shift toward relaxation-controlled diffusion, as the diffusion exponent 'n' decreased from 0.469 to 0.407 in toluene, while the diffusion coefficient 'D' increased from 3.48×10⁻⁴ to 5.16×10⁻⁴ cm²/s, indicating the formation of interfacial channels. Two-way ANOVA (p < 0.001) confirmed that both filler content and solvent composition significantly influenced the results. The results indicates that silica ash enhances network density and solvent resistance through filler-polymer interfaces, offering a sustainable solution for PDMS composites in demanding chemical environments.