Preparation and properties of crosslinkable waterborne polyurethane and polyurethane-acrylic hybrid emulsions and their crosslinked polymers

Abstract

Stable emulsions of crosslinkable waterborne polyurethanes (CWPU) and waterborne polyurethane-acrylic (CWPU/AC) hybrid with various contents of trifunctional monomer (trimethylolpropane, TMP) and acrylic monomers were successfully prepared in this study. This study focused on the effects of crosslinkable TMP and acrylic monomer contents on the stability/average particle size/viscosity of CWPU and CWPU/AC hybrid emulsions, the mechanical/dynamic mechanical thermal properties, surface contact angle/tension and hardness/water swelling of CWPU and CWPU/AC hybrid film materials. The as-polymerized CWPU emulsion containing 0.06 mol (4.11 mol%) of TMP and CWPU/AC hybrid emulsion containing 60 wt% of acrylic monomer were found to be unstable, indicating that these contents were beyond the limit value of the self-emulsifying ability of dimethylol propionic acid (18.26 mol%). By XPS analysis, CWPU and CWPU/AC film samples were found to have silicone/fluorine enriched surface. The tensile strength/modulus/hardness of the film samples increased markedly with increasing crosslinkable TMP/acrylic monomer up to 0.04 mol/50 wt%, respectively. Meanwhile the elongation at break and water swelling % decreased significantly. The water/ethylene glycol contact angles increased/the surface tension decreased significantly with increasing crosslinkable TMP/acrylic monomer contents up to 0.04 mol/50 wt%. Thus, the optimum TMP/acrylic monomer contents were found to be about 0.04 mol/50 wt% to obtain high performance antifouling coating materials.