Stretchable Film Surface Siloxane Localization for Strength and Repellency

The patent uses a composite material system combining polyurethane resin and silicone resin in specific proportions (polyurethane 70-95 wt%, silicone 5-30 wt%). The polyurethane provides the primary stretchability and strength, while the silicone resin is surface-localized to provide hydrophobicity and resistance to hydrolysis, creating a synergistic effect that resolves the contradiction between mechanical properties and chemical stability.

The patent creates local quality differentiation by having silicone resin localized primarily on the surface of the coating film while polyurethane forms the bulk structure. This is achieved through controlled composition and curing processes that cause silicone to migrate to the surface. The surface region thus provides hydrolytic stability and repellency, while the interior provides mechanical strength and stretchability.

The patent creates a composite coating system where silicone resin (5-30 wt%) provides surface repellency through its hydrophobic properties, while polyurethane resin (70-95 wt%) provides the structural framework for mechanical strength. The combination allows the coating to exhibit both high repellency from the silicone-rich surface and high strength from the polyurethane bulk structure.

The patent achieves local quality by concentrating silicone resin at the coating surface where it provides repellency, while the polyurethane forms the stronger interior structure. This spatial separation of functions allows the coating to simultaneously achieve high surface repellency and high overall strength without compromise.

The patent changes the compositional parameters by using a much higher proportion of polyurethane resin (70-95 wt%) compared to silicone resin (5-30 wt%), and specifically controls the ratio of polyurethane to silicone to be 7:3 to 19:1. This parameter optimization ensures that while crosslinking provides strength, the surface remains sufficiently silicone-rich to provide high repellency, avoiding the intermediate property problem.

The patent maintains local quality differentiation even with crosslinkable resins by controlling the composition and curing process to ensure silicone components localize at the surface. The crosslinked polyurethane interior provides strength and adhesiveness, while the silicone-rich surface maintains high repellency, preventing the uniform dispersion that would result in intermediate properties.