Cardanol derived P and Si based precursors for flame retardant PU coatings
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. A new 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. Characterisation 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 characterisations showed that the required products have been formed.
Flame-retardant coating from cardanol
The coated films showed similar mechanical properties which were analysed 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.
The study is published in: Progress in Organic Coatings Volume 129, April 2019, Pages 59-68.