Novel glycerol-based polymerized flame retardants with combined phosphorus structures for preparation of high performance unsaturated polyester resin composites

Owing to poor flame retardant efficiency and compatibility of traditional flame retardants, it is difficult to prepare unsaturated polyester resins (UPR) composites with excellent flame retardant properties. In this research, novel glycerol-based polymeric flame retardants (PCH3PG, PBPG and POPG) were synthesized. The effect of different side chains, phosphorus contents and combined structures on flame retardancy efficiency of UPR composites were explored. It has been found POPG was more conducive to improving char formation under high temperatures than PCH3PG and PBPG. However, PCH3PG and PBPG exhibited better flame retardant efficiency in flame retaradant UPR composites. Especially for UPR/PCH3PG, the flame retardant performance increased rapidly with increasing PCH3PG contents. With only 15 wt% of PCH3PG in UPR, UPR/PCH3PG 15% reached UL-94 V0 and 29% of LOI. When PCH3PG contents increased to 20 wt%, the LOI of UPR/PCH3PG 20% increased to 30%, and PHRR and THR were reduced by 67.93% and 57.22%, compared with pure UPR. The thermal degradation products and flame retardant mechanism in gaseous and condensed phase were studied. It was found the most efficient PCH3PG was mainly played flame retardant effect in gaseous phase, supplemented by the barrier effect of condensed phase. Additionally, the polymeric glycerol-based flame retardants exhibited good compatibility with UPR matrix. This work explores the high-efficiency flame retardant structures with good compatibility for UPR, promoting the wide application of UPR materials.