Effect of Solid Content on Rheological, Mechanical, and Thermal Properties of Adipic Acid‐Based Flame Retardant Polyurethane Dispersion

The solid concentration of polyurethane dispersion is an important aspect of the coating application. In the present work, anionic waterborne polyurethane was prepared by reacting PPG‐100, adipic acid, and THPP‐based monophosphate polyester diol with IPDI. The formulation was done by varying solid concentrations of dispersion. The chemical structure was confirmed using FTIR and NMR. The surface morphology of coated panels was analyzed by SEM that shows as solid concentration increases surface roughness increases. The rheological property indicates that the solid concentration of FRPUDs increases viscosity and storage modulus whereas loss modulus decreases. The thermal degradation rate increases from 348°C to 354°C with increased solid concentration. LOI increases from 26% to 29% with increase in solid concentration. Tensile strength increases from 10.5 to 14.8 MPa with an increase in solid concentration in dispersion. Flexibility or elongation increases from 268% to 299% with a decrease in solid concentration. Scratch hardness in coating increases with increase in solid concentration.