Preparation and properties of waterborne polyurethane/epoxy resin composite coating from anionic terpene-based polyol dispersion

• An anionic polyol dispersion was synthesized from biomass based epoxy resin.
• A waterborne polyurethane/epoxy resin composite coating was prepared as 2K-WPU form.
• The particle merging mechanism of the film formation was validated with AFM.
• The composite product had good mechanical and thermal-resistant properties.

An anionic polyol (T-PABA) dispersion was prepared by modifying terpene-based epoxy resin with para-aminobenzoic acid. Then T-PABA dispersion was crosslinked with a hexamethylene diisocyanate (HDI) tripolymer to prepare waterborne polyurethane/epoxy resin composite coating. The rheological properties and particle size distribution of the composite system were characterized by rotary rheometer and laser particle size analyzer. The crosslinked composite product has good thermal resistant properties, with glass-transition temperatures (Tg) about 40% and 50% weight loss temperatures (Td) in the range of 400–420. The smooth and transparent film obtained from the composite product has good flexibility, adhesion, impact strength, antifouling and blocking resistance properties. The impact strength, pencil hardness, water-resistant and thermal-resistant properties of the composite products increased with the molar ratio of isocyanate group to active hydrogen of T-PABA.