Waterborne hybrid polyurethane coatings containing Casein as sustainable green flame retardant through different synthesis approaches

Waterborne polyurethane (WPU) dispersions were prepared for flame retardant coatings. Specifically, alkoxysilane-capped polycaprolactone-based WPUs synthesized employing the acetone process, and Casein, as a green sustainable additive, was added by two different methods (in situ ex situ). These strategies made possible to evaluate effect of Polyurethane/Casein interaction in final properties films. FTIR solid-state 29Si NMR, confirmed formation siloxane network during film generation process. The addition Casein synthesis situ) resulted covalent bonding between which significantly increased particle size. However, incorporation after phase inversion WPU (ex situ), did not change Tensile tests revealed that bond promoted an increase brittleness material compared approach due better dispersion system. TGA results showed thermal stability all coatings, especially those obtained route. Moreover, according microscale combustion calorimeter (MCC) vertical burning test (UL-94) measurements delayed material. Consequently, their characteristics, these Casein-WPU could potentially be used where good physicochemical are essential effective performance.