Damage-specific evolution of a fluorine-free PDMS/TPU–ZnO coating on nylon/spandex fabric: Differential responses of Si-containing surface species and ZnO-rich surface features

Abstract

Fluorine-free textile coatings require durable surface chemistry and particle-derived architecture, yet their damage-specific evolution is poorly resolved by static contact angles alone. Polydimethylsiloxane, thermoplastic polyurethane and silane-treated zinc oxide were deposited on nylon/spandex fabric by dip–pad–dry–cure processing and evaluated through sequential screening, spectroscopy, microscopy, elemental analysis and complementary wetting tests. The selected coating reached an apparent water contact angle of 144.87° in screening; separate probe-liquid measurements showed a diiodomethane contact-angle increase from 48.35° to 87.59°, while representative trajectories for pristine, washed and abraded coatings retained 97.3–99.1% of their respective 5-s water angles at 200 s. After 30 washing cycles, the local Zn/Si index was 5.45 (89.6% of the pristine value of 6.08), compared with 2.63 after 2000 Martindale cycles, with Si detectable at 2.46 wt% in the analysed abraded region and the representative 200-s water angle decreasing from 127.3° to 112.9°; no roll-off at 90° was observed in the tilt tests. These observations are consistent with preferential depletion of ZnO-rich surface features while Si-containing species remain detectable, revealing a strongly pinned hydrophobic state and suggesting particle–binder anchoring and controlled embedding as design variables for further evaluation.