Synergistic Enhancement of Hydrophobicity and Hardness in Fluorosilicone Acrylate/Polysilazane Hybrid Coatings via Siloxane Cross-Linking

Abstract

Polysilazane (PSZ) has attracted significant attention in protective coatings because it can convert into dense silicon oxide layers at relatively low temperatures. However, poor compatibility between PSZ and fluorinated acrylates has limited the practical application of such composite systems. To address this issue, KH570 was introduced as a functional comonomer to prepare KH570-modified fluorosilicone acrylate polymers (PFSn). These polymers were blended with PSZ to combine low surface energy with the high hardness characteristic of PSZ. During curing, the siloxane groups in PFSn undergo hydrolysis and condensation with PSZ, forming a dense Si–O–Si cross-linked network. Meanwhile, the fluorinated segments spontaneously migrate and accumulate at the coating surface, which leads to low surface energy. By adjusting the contents of KH570 and PFS4, the balance among surface energy, mechanical properties, and antigraffiti performance was optimized. Under the optimal formulation (PFS4-3), the coating achieved a water contact angle of 107.2°, a total surface energy of 15.0 mN/m, a pencil hardness of 5H, and an adhesion rating of grade 1. It also showed good antigraffiti performance against methylene blue solution and oil-based markers. The recommended service temperature is below 240 °C. Overall, this work provides a useful experimental reference for formulation optimization of fluorosilicone composite coating systems.