Influence of a Siloxane-Modified DOPO Derivative on the Properties of Polyurethane Cationomer Coatings

Waterborne polyurethane cationomer coatings modified with 1,3-bis(3(3-(propoxy-2-ol-)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide)-3-propyloxy))tetramethyldisiloxane (TMDS-AGE-DOPA) containing phosphorus and silicon atoms were obtained. Their structures were confirmed by Fourier transform infrared (FTIR) spectroscopy. The effect of TMDS-AGE-DOPA on thermal properties, flame retardancy, and surface characteristics (gloss, contact angle, surface free energy), as well as performance properties (hardness, impact resistance), was investigated. A coupled TG-FTIR technique was employed for evolved gas analysis. Thermal stability decreased with the addition of the modifier, while the glass transition temperature increased from -19 to 25 °C. The modifier improved the flame retardancy of the material by shifting the peak temperature of the heat release rate (T_PHRR) to lower values. The gloss of the coatings was very high (>90 GU at all angles studied), although it decreased with increasing modifier content. The presence of phosphorus moieties from the modifier enhanced hydrophilicity, raising surface free energy (SFE) from 37.9 to 44.0 mJ/m². The coatings are soft materials with a Persoz hardness in the range of 0.05-0.32. The modifier increased hardness but reduced impact strength. The obtained cationomers can be applied as environmentally friendly coatings on hydrophilic surfaces such as textiles, glass, or wood.