Preparation and Characterization of Efficient Flame-Retardant and Thermostability Two-Component Aqueous Varnish Coatings

A method to prepare efficient flame-retardant two-component waterborne polyurethane coatings by combining polyepichlorohydrin, polypropylene glycol, isocyanate, chain-extender and curing agent was developed. The structures and properties of latexes and films were determined by grain size, viscosity, FTIR, differential scanning calorimeter, mechanical properties, thermogravimetry, flame-retardant and applicant measurements. The results illustrated that the more the hydrated double electric layer of two-component varnish coatings latex particles was, the better the resulting mechanical and chemical stability was. The grain size increased and viscosity decreased as stoichiometric ratio of –OH to –NCO became larger. The lower T_gs and higher T_gh were attributed to the polar extender which hindered aggregation of soft segment in order to accelerate the more drastic movement of the polymer chain. The nonflammability of char layer was weakened as stoichiometric ratio of –OH to –NCO became larger, thus reducing flame-retardant and thermal stability. The limit oxygen index values of all materials exceeded 30%. The two-component varnish coatings had a pretty good water and solvent resistance.