Flame retardation behaviors of UV-curable phosphorus-containing PU coating system

Abstract

<jats:title>Abstract</jats:title> <jats:p>A UV-cured polyurethane (PU)/nano-silica composite with a flame-retarded coating system was obtained from the composition of nano-silica containing a UV-curable PU oligomer and a UV-reactive phosphonic acid [ethylene glycol methacrylate phosphate (EGMP)]. The UV-curable PU oligomer was prepared by an addition reaction of 2-hydroxyethyl methacrylate (2-HEMA) with an NCO-terminated PU pre-polymer; this was then mixed with a methanol dispersion of nano-silica. The UV-reactive phosphonic acid (EGMP) was prepared by a reaction of 2-HEMA with phosphorus pentoxide (P<jats:sub>2</jats:sub>O<jats:sub>5</jats:sub>). The curing reaction of the PU/nano-silica composite coating system was carried out by UV irradiation with the aid of a photoinitiator (2-hydroxy-2-methylpropiophenone). The thermal properties of these PU/nano-silica composite coatings were investigated by the measurements of dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA), respectively. A phosphorus (phosphonic acid) containing ingredient, EGMP in PU coating system that provides good adhesion to steel surface and flame retardation. Their physical properties (contact angle, hardness) and flame flammability [limiting oxygen index (LOI), UL-94 test] with various phosphorus contents (different dosages of EGMP) were also evaluated in this report.</jats:p>

Overview of Silica-Polymer Nanostructures for Waterborne High-Performance Coatings

“…Hybrid nanoparticles offer huge design flexibility for the design of coatings with a wide range of properties, improving not only the mechanical properties (e.g., impact, abrasion, or scratch) and chemical resistance (e.g., against oxidation and hydrolysis resulting from exposure to sunlight, air, and water), but also providing new functionalities ( Table 3 ) [ 4 , 9 ]. Desirable properties in waterborne coatings include flexibility [ 29 , 88 , 117 ], adhesion [ 81 , 118 , 119 ], wear resistance [ 92 , 102 , 120 , 121 , 122 ], and durability [ 120 ]. Among the possibilities for added coating functionality are, for example, flame retardancy [ 119 ], solvent and chemical resistance [ 123 , 124 ], stain resistance [ 102 , 124 ], anti-cavitation [ 81 ], extreme robustness (for space-based applications) [ 125 ], antimicrobial activity [ 126 , 127 , 128 , 129 , 130 , 131 ], superhydrophobicity [ 84 , 95 , 124 , 132 , 133 , 134 , 135 , 136 , 137 , 138 ], or photoactive fluorescent coatings [ 29 ] presented in Table 3 .…”

“…Often, the use of SNPs can improve different coating properties and simultaneously add new functionalities. For example, SNPs increase the T g and hardness of polyurethane composite films, containing ethylene glycol methacrylate phosphate (EGMP), with the resulting material presenting also good adhesion to steel surfaces and flame retardancy [ 119 ]. In fact, silica-containing epoxy composites are already used in adhesives, paints, solvent and chemical resistance, and marine coating technology [ 118 , 123 , 130 ].…”