Methyltrimethoxysilane Vapor Deposition Strategy for Preparing Superelastic and Hydrophobic Flexible Polyurethane Foams

Flexible polyurethane foam (FPUF) is widely used in buffer protection, biomedical, and wearable fields due to its light weight, high resilience, and adjustable mechanical properties. However, the traditional water foaming system is often accompanied by bottleneck problems such as cyclic fatigue attenuation, insufficient thermal stability, and surface hydrophilicity while achieving low density. In this study, a dense Si-O-Si cross-linked layer was in situ constructed on the surface of the foam by systematically regulating the water content of the foaming agent (1.5~2.5 wt%) and coupling with methyltrimethoxysilane (MTMS) chemical vapor deposition. Experiments show that the foam foamed with 2 wt% water content still maintains 0.0466 MPa compressive strength and 0.0532 MPa compressive modulus (modulus loss is only 16.6%) after 500 cycles of compression at 90% strain after MTMS deposition. MTMS modification drives the surface wettability to change from hydrophilic (70.4°) to hydrophobic (128.7°), and significantly improves thermal stability (the carbon residue rate at 800 °C increased to 25.5%, an increase of 59.4%). This study not only improves the resilience, but also endows the FPUF surface with hydrophobicity and thermal protection ability, which provides the feasibility for its wide application.