Flame Retardance, Smoke Suppression, Hydrophobicity and Microphase Separation of Waterborne Polyurethane Containing Polyphosphate and Silicone Diol

A kind of waterborne polyurethane with good flame retardancy, smoke suppression, hydrophobicity and strength improvement using phosphorus-based and silicon-based diols as reactive flame retardants (WSPPU) was synthesized and characterized. The LOI value of WSPPU has increased from 19.1% to 28.5%, and the UL-94 rating reaches V-0. Cone calorimeter testing shows that the peak heat release rate ( p HRR) and the peak smoke generation rate ( p SPR) of WSPPU are 348 kW/m 2 and 0.03 m 2 /s, reduced by 57.9% and 82.4% compared with pure WPU respectively. During the thermal decomposition process of WSPPU, a stable and dense carbon layer containing  P(O)  O  Si is formed, endowing WSPPU with more outstanding heat insulation and smoke suppression performances. The water contact angle of this film reached 98.5° due to the formation of a hydrophobic surface derived from the migration of the silicone segments to the surface as demonstrated by XPS. DMA shows that the coexistence of polyphosphate and silicon segments can adjust the degree of microphase separation of polyurethane, enabling polyurethane to have a greater tensile strength of 25.56 MPa with a 26.64% increase relative to neat WPU. The obtained waterborne polyurethane has excellent comprehensive performance and shows great application potential in the industrial field.