Halogen free organic coatings for flame retarding applications using phytic acid conjugated UV-curable resin

In this work, we report the synthesis and characterization of a new flame-retardant (FR), UV-curable resin, covalently stabilized with non-halogenated FR-additive, phytic acid (PA) for coating variety of substrates. Incorporation of polyphosphate-rich compounds, such as PA, in an organic coating formulation is a challenging task. The UV curable FR-resin was prepared by reacting PA with isophorone diisocyanate to form a poly-isocyanate, which was further reacted with hydroxymethyl acrylate to produce methacrylated urethane resin (phyto-urethane-acrylate, PUA). To the best of our knowledge, this is the first-time report of phosphorous-rich, urethane-based polyacrylates, synthesized with PA as the core molecule. Upon application on metal substrates, PUA resin was UV-cured using a photo initiator, Omnirad 1173. Surface coatings prepared using the PUA resin showed superior mechanical and thermal properties compared to coatings prepared with a commercially available resin, Ebecryl 8402. A proof-of-principle cone calorimetry studies showed that PUA based coatings demonstrated 30 % lower peak heat release rate (PHRR), 25 % lower total heat release (THR) and "Good" flame retardancy index (FRI) properties (PUA100/T0 – 1.70 and PUA80/T20 – 2.20) compared to control coatings prepared with commercially available resins. The synthetic route established in this report will enable the use of bio-based FR-additives for a wide-range of coating applications.