Polyfunctional phytic acid-based reactive diluent for UV-curable coating with improved flame-retardant performance and toughness

The shortcomings of oligomer resin, including its high viscosity, easy brittleness and lack of flame-retardant performance, obviously limit the application fields of the related coatings. Herein, a UV-curable polyfunctional biomass-based diluent (PAGMA) is conveniently and effectively synthesized by grafting glycidyl methacrylate onto phytic acid. The structural characterization of PAGMA is identified by FT-IR and 1H NMR tests. Moreover, PAGMA diluent is mixed with UV-curable epoxidized soybean oil-based acrylic resin (ESO-based resin), and the influences of PAGMA on the viscosity of ESO-based resin, the mechanical property and the flame-retardant efficiency of the related films are systemically researched. All results demonstrate that the viscosity of composite resin (R2 resin) with 20 wt% PAGMA reduces by 39.2% compared with that of ESO-based resin. And the toughness of the cured film (F2 film) prepared by R2 resin achieves about 1.18 MJ·m-3, which is 2.26 times as large as the cured film prepared without PAGMA (F0 film). Furthermore, the limiting oxygen index value of F2 film improves by 31.2% compared with that of F0 film, and the F2 film can self-extinguish after being ignited. Thus, the prepared polyfunctional biomass diluent can be applied to UV-curable coatings to decline the coating viscosity and enhance the comprehensive properties of coating films, which assists in broadening the application fields of UV-curable materials, especially in fire prevention.