New hybrid waterborne polyurethane/acrylate (WPUA) dispersions were synthesized by grafting with bisphenol-A-glycidyl dimethacrylate (Bis-GMA) in order to create chemical bonds between polyurethane and polyacrylate chains. WPUAs were prepared by using prepolymer self-emulsifying method with isophorone diisocianate, poly(tetramethylene ether) glycol, dimethylolpropionic acid, and ethylenediamine in the polyurethanic part, and styrene and n-butyl acrylate in the polyacrylate portion. A redox pair system consisting of ascorbic acid and hydrogen peroxide were used as polymerization initiator. The particle size of the WPUA dispersions increased by increasing the Bis-GMA/1,4 butanediol ratio, stable dispersions of negatively charged particles were obtained, and they had low viscosity (around 1.3 mPa.s) in spite of the relatively high solids content (27 wt%). Higher thermal stability was obtained when 50 mol% of chain extension was carried out with Bis-GMA. Using Bis-GMA/BD, instead of HEMA, as grafting agent, allowed obtaining hybrid polyurethane dispersions with the lowest mean particle size and better colloidal stability. Finally, the addition of 35 wt% Bis-GMA increased noticeably the cross-cut adhesion of polyurethane/acrylate coatings to stainless steel.
Volume 118, May 2018, Pages 30–39