Cardanol derived P and Si based precursors to develop flame retardant PU coating

[Display omitted] •Cardanol is used as a bio-resource.•Synthesis of novel P and Si based precursors.•Synthesized precursors are successfully incorporated in the PU backbone for the flame-retardant applications.•Limiting oxygen index (LOI) achieved is 29 for the coating formulation with the equal concentrations of precursors.•All the coatings retained good mechanical properties even with the incorporation of the precursors in the system. In the evolving resin world, people are trying to develop the resins from bio-resources with the properties similar to or superior to the commercial resins. This research work presents an attempt to develop the flame-retardant coating from cardanol as a starting material. The two intermediates obtained using Phenylphosphonic dichloride (PPDC) and Dichlorodimethylsilane (DCDMS) are used in the development of polyurethane backbone in various proportions. Itaconic acid (IA) based polyol was used as a chain extender for curing. Characterization of the intermediates obtained was done using the Fourier transform infrared (FTIR) spectroscopy, Nuclear magnetic resonance (NMR) spectroscopy, acid value, hydroxyl value, epoxy value, etc. All the characterizations showed that the required products have been formed. The Coated films showed similar mechanical properties which were analyzed using flexibility, impact resistance and pencil hardness. The gel content and water absorption values obtained are inversely proportional to each other which can be correlated with the barrier properties of the films. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) showed that the FR50 produced the maximum amount of char and FR100 had the highest Tg with the value of 81.68 °C. Flame retardancy of the cured films was checked using the limiting oxygen index (LOI) and UL- 94 vertical burning test. All the coating films with the developed precursors were able to self-extinguish the fire within 10 s and FR50 obtained 29 as the highest value of LOI.