Emulsion-Templated Siloxane-Collagen-Surfactant Porous Composite for Footwear Cushioning Applications

Abstract Lightweight elastomeric composites with tunable viscoelastic response are essential for advanced energy-management cushioning applications. However, achieving controlled modulation between damping and elastic recovery remains challenging in silicone-based polymeric systems. Herein, polydimethylsiloxane (PDMS) was structurally engineered through a synergistic multiphase approach encompassing: (i) reinforcement with collagen fibers (CF) derived from leather waste, (ii) incorporation of polyphenylmethylsiloxane (PPMS) to modulate segmental dynamics, and (iii) surfactant-assisted (S) morphological control. This integrated strategy enabled systematic regulation of composite density, mechanical compliance, and cyclic hysteresis behavior, offering a route to tunable viscoelastic response in silicone-based systems. Scanning electron microscopy revealed a highly porous structure with uniform spherical pores in the optimized CF-PD-PP-S composite, while magnetic resonance imaging confirmed a partially open-cell structure with enhanced pore accessibility throughout the bulk. X-ray photoelectron spectroscopy verified the successful incorporation of collagen fibers, PPMS, and surfactant, indicating optimal formulation. The progressive modification induced a transition from damping-dominant to resilience-dominant mechanical response, with the optimized CF-PD-PP-S composite exhibiting low hardness (26 ± 2 Shore OO), reduced density (0.55 g/cm3), controlled cushioning energy (128–205 mJ), minimal compression set (2.77%), and stable cyclic recovery (85% resilience; 15% dissipation). The reduced hysteretic loss during repeated short-term loading suggests that the composite retained a stable mechanical response after repeated loading. The results establish a materials design strategy for tailoring energy dissipation and recovery balance in PDMS-based elastomeric composites for footwear cushioning applications.