Development of flame-retardant waterborne polyurethane dispersions (WPUDs) from sulfonated phosphorus-based reactive water-dispersible agents

The current study presents an attempt to develop two molecules, namely sulfonated aromatic diol (SAD) and sulfonated aromatic diamine (SADAM), to induce flame retardancy, thermal stability, and dispersion ability for water-based polyurethane dispersions (WPUDs). The previously reported itaconic acid-based polyester polyol was used for prepolymer synthesis as well as for chain extension. Pre- and post-sulfonated compounds were subjected to characterization tests such as FTIR, 13C-NMR, 1H-NMR, and CHNS for confirmation of their structures. The standard dispersant used for the basis of comparison was commercially available dimethyl propionic acid (DMPA). WPUDs were synthesized in different molar concentrations of DMPA, SAD, and SADAM, and the covalent incorporation of all three molecules in the polymer backbone was confirmed by FTIR. The WPUD films were subjected to various thermal tests like TGA and DSC as well as mechanical tests like flexibility and pencil hardness. WPUD films obtained from SADAM showed a remarkable increase in Tg as well as char content. The THRI values for SAD- and SADAM-based films were better than DMPA-based films. SAD- and SADAM-based WPUD films also showed an increase in LOI value and UL-94 ratings with the maximum LOI value of 26. Dispersions based on DMPA showed better stability as compared to dispersions based on SAD and SADAM.