Optimization of linear attenuation coefficients and characterization of mechanical and thermal properties in silica ash-reinforced PDMS composites

Abstract This investigation engineers multifunctional polydimethylsiloxane (PDMS) composites incorporating 0–50 wt% silica ash a valorized industrial byproduct as lightweight, sustainable gamma-ray shielding elastomers. Narrow-beam attenuation experiments spanning diagnostic-to-isotope energies (59.5-1332.5 keV) quantify a monotonic enhancement in linear attenuation coefficients (µ), escalating from 0.3011 cm⁻¹ (pure PDMS) to 0.3651 cm⁻¹ (50 wt% ash) at 59.5 keV, with concomitant reductions in half-value layer (HVL) from 2.30 cm to 1.90 cm. This stems from a paradigm shift in photon interaction physics: photoelectric dominance (< 100 keV) amplifies via elevated effective atomic number (Z eff ), transitioning to density-mediated Compton scattering (≥ 661.66 keV), validated by < 3.76% deviation from NIST XCOM photon cross-sections. Lead-equivalence analysis reveals the 50 wt% composite demands merely 10–14× lead thickness in the Compton regime, underscoring superior mass efficiency. Hierarchical microstructural analysis (SEM, EDX, XRF) elucidate homogeneous nanofiller dispersion and robust siloxane-filler interfacial coupling, driving progressive stiffening (Young’s modulus: 0.026 to 0.157 MPa at 40 wt%). Optimal mechano-elastic performance manifests at 15 wt% (tensile strength: 0.357 MPa; toughness: 0.591 MJ·m⁻³), beyond which agglomeration induces embrittlement. Thermogravimetric profiles reveal an initial stabilization peak at 10 wt% ash, followed by catalytic depolymerization at higher loadings, rationalized by Lewis acid-base interactions accelerating Si-O bond scission despite augmented char residue. These composites (optimized at 10–20 wt%) exhibit enhanced radiation attenuation together with improved mechanical resilience and elastomeric flexibility, demonstrating their potential for flexible radiation shielding applications.