Flame resistance, physical and mechanical properties of UV-cured hybrid coatings containing low-hydroxyl-content sols via an anhydrous sol-gel process

As one of a series of our studies, starting with silica sol (TM2) and Si-P binary sol (SP5), two series of low-hydroxyl-content sols (LHCSs) were synthesized using an anhydrous sol-gel method. The stable storage time of LHCS-containing hybrid coatings was improved relative to that of hybrid coatings containing TM2 and SP5. The flame resistance and thermal stability of UV-cured hybrid coatings consisting of LHCS, epoxy acrylate of bisphenol A (SM6104) and tripropylene glycol diacrylate (TPGDA) were investigated by means of thermogravimetric analysis (TGA), limit oxygen index (LOI), cone calorimetry and a flammability test. The results indicated that the flame resistance of LHCS-containing hybrid coatings was further improved over that of hybrid coatings containing TM2 and SP5. The improvements mainly included a longer ignition time and lower combustion heat. Hybrid coatings applied on the surface of wooden floors could offer long-lasting and significant protection against fire, showing outstanding practical value. In addition, the physical and mechanical properties of LHCS-containing hybrid coatings were negatively affected by the decrease of hydroxyl group contents and the Ti-containing component. A UV-curable phosphorus-containing resin (RAYLOK 1722) was introduced into the hybrid coatings containing LHCS. However, hybrid coatings containing RAYLOK 1722 showed only a small improvement in flame resistance, and their physical and mechanical properties were damaged by RAYLOK 1722.