Structural design of flame‐retardant phosphatized unsaturated polyester resin

Abstract To improve flame‐retardant properties of unsaturated polyester resin (UPR), two phosphorus‐containing vinyl monomers with different chemical structures were synthesized to replace styrene molecules and then copolymerized with UPR oligomers to prepare flame‐retardant phosphatized UPRs. Curing behavior of phosphatized UPRs was investigated by DSC non‐isothermal curing curves, deducing the best curing conditions. Cone calorimeter results demonstrated the obvious reduction of heat release rate and smoke production rate by comparing phosphatized UPRs with flammable UPR. TG‐IR‐MS coupling technique was utilized to reveal thermal degradation and pyrolytic volatiles including aromatic compounds, hydrocarbons, CO, PO 4 ˙, and so forth, providing more information of smoke toxicity and the gas phase flame‐ retardant mechanism of phosphatized UPRs. Moreover, the yield, compactness and graphitic degree of char residues of phosphatized UPRs were increased, strengthening the barrier effect to inhibit the permeation of combustion heat and the effusion of pyrolytic volatiles in the condensed phase.