/ Curing Thermosetting Epoxy Halogen-free Flame Retardant

Epoxy resin is one of the most widely used and versatile materials in the world today. Combined with various unique properties, epoxy resins have been successfully applied in coatings, adhesives, composites, electronics and civil engineering, etc. However, the lack of flame retardance has limited their applications. The present thesis was aimed on the development of halogen-free flame retardants used in epoxy systems. A novel hyperbranched polyphosphate ester (HPPE) was synthesized and used as a multifunctional curing agent for bisphenol A epoxy resin. The thermostablity and flame retardace of the cured epoxy thermosets were studied. The thermal decomposition kinetics of epoxy resins containing HPPE and phenolic melamine (PM) was evaluated by different kinetic methods. Two aromatic acrylated phosphonate monomers were also synthesized and applied in UV curable coatings in this thesis. Photo-curing properties, thermal degradation process/mechanism and flame retardance of epoxy acrylate resin blended with the acrylated phosphonate monomers were investigated. The detailed outline is elaborated as follows:Through the polycondensation of bisphenol-A as an A₂ monomer and phosphoryl trichloride as a B3 monomer, a novel hyperbranched polyphosphate ester (HPPE) was synthesized via the "A₂+B₃" approach. ³¹P NMR spectroscopy was used to monitor the reaction process. The formed HPPE was characterized by FTIR and ¹H NMR to confirm its end groups. The differential scanning calorimetry data revealed that the cured bisphenol-A epoxy resin with HPPE as a curing agent possessed improved glass transition temperature. Dynamic mechanical thermal analysis also showed the increase of the glass transition temperature. The thermal degradation properties and flame retardancy were investigated by thermogravimetric analysis (TGA) and limiting oxygen index (LOI). The obtained results showed that the incorporation of HPPE into bisphenol-A epoxy resin increased its thermostability and char yield during the decomposition by raising the second stage decomposition temperature. The LOI value significantly increased with the addition of HPPE.