Synthesis and properties of waterborne fluorinated polyurethane-acrylate using a solvent-/emulsifier-free method

Pristine waterborne polyurethane-acrylate [pristine WPUA, soft-segment content: 64 wt%, dimethylol propionic acid (DMPA): 20 mol%/4.95 wt%] emulsions were synthesized using an acetone process from 4,4′-dicyclohexymethane diisocyanate (H12MDI)/poly(tetramethylene oxide glycol) (PTMG,2900 g/mol)/DMPA/2-hydroxyehthyl metacrylate (HEMA) without an external emulsifier. A series of waterborne fluorinated polyurethane-acrylate hybrid [WFPUA: WFPUA10, WFPUA20 WFPUA 30 and WFPUA 40, where the numbers indicate the total content of acrylic monomers] emulsions as antifouling coating materials were synthesized from vinyl group-terminated urethane prepolymer (pristine WPUA components)/[isobornyl acrylate (IBOA)/n-butyl acrylate (BA)/perfluorodecyl acrylate (PFA) (IBOA/BA/PFA: 4/3/3 wt ratio)] by radical polymerization using an emulsifier-free/solvent-free method. The as-polymerized hybrid emulsion containing 50 wt% of acrylic monomer content was found to be unstable, indicating that near 50 wt% of acrylic monomer content was beyond the limit value of self-emulsifying ability. The gradient concentration of fluorine in the film structures from the film-air surface to the film-dish interface was characterized by Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy. As the total acrylic monomer/PFA content of hybrid materials increased, the water/methylene iodide-contact angles, lower temperature Tg and elongation at break increased, however, the higher temperature Tg, water swelling, tensile strength/modulus and hardness decreased. The contact angles of hybrid film samples increased with increasing total acrylic monomer/PFA content up to about 30 wt%/9 wt%, and then almost leveled off. The optimum total acrylic monomer/PFA content was found to be about 30 wt%/9 wt% to obtain high performance water/oil repellent coating materials.