Hydrogen Bonding Regulation toward High-Performance Waterborne Fluoroethylene-Vinyl Ether (FEVE) Fluorocarbon Coatings via Blocked Isocyanates

Abstract

Waterborne fluoroethylene vinyl ether (FEVE) fluorocarbon coatings represent an attractive platform for high-performance protective applications, offering significant advantages in reducing organic solvent usage and improving environmental and human health safety. However, their practical development is critically hindered by inherent incompatibilities: the low surface energy of fluorinated latex particles and the poor water compatibility of conventional isocyanate curing agents often lead to defective film formation, including mismatched cross-linking, phase separation, porosity, and cracking. To address these challenges, we designed and synthesized a hydrogen-bond-enriched latent curing agent based on adipic dihydrazide (ADH)-modified methyl ethyl ketoxime (MEKO)-blocked hexamethylene diisocyanate (HDI). Thermal analysis revealed that low ADH contents preserve the primary melting behavior of HDI-MEKO at approximately 76–77 °C, while maintaining the main thermal activation within 150–200 °C, supporting a ″film formation prior to deblocking cross-linking″ curing mechanism. Comprehensive coating evaluations demonstrate that low-to-moderate ADH incorporation achieves an optimal balance among film morphology, adhesion, hardness, hydrophobicity, and chemical resistance. Notably, HDI-MEKO-05-F and HDI-MEKO-15-F films exhibit relatively smooth morphologies, grade 0 adhesion, and a 4H pencil hardness. This study provides a feasible and effective strategy for coordinating latex film formation, thermal deblocking, and chemical cross-linking, thereby facilitating the development of advanced, high-performance waterborne FEVE coatings.