Flammability behavior of unsaturated polyesters modified with novel phosphorous containing flame retardants

Two phosphorous containing reactive flame retardants namely Triallyl phosphate (TAP) and diethylene glycol modified tetra‐allyl phosphate (DTAP) are synthesized and incorporated successfully in commercial Unsaturated polyester (UPR) in various amounts (5, 10, and 15 phr) to yield flame retardant unsaturated polyester (FRUPR) composites. The structures of reactive flame retardant monomers are confirmed by FTIR, ¹H‐NMR, and³¹P‐NMR spectroscopy. Further, FRUPR composites are characterized for their mechanical, thermal, and flame retardant properties. It is observed that tensile strength and hardness of composites are enhanced with the addition of flame retardants; however, flexural strength and impact resistance are lowered. Differential Scanning Calorimetry (DSC) study reveals that there is a significant increase in glass transition temperature with the addition of flame retardants suggesting the formation of dense and crosslinked structure in FRUPR composites. Thermal stability and the flame retardant properties are also observed to be improved with the increase in concentration of flame retardant in UPR as evidenced from Thermo‐gravimetric analysis (TGA). Beyond 10 phr concentration of flame retardants, all composites show V‐0 rating on UL‐94 test. Also, increase in phosphorous content in composites leads to gradual improvement in limiting oxygen index values. POLYM. COMPOS., 38:1483–1491, 2017. © 2015 Society of Plastics Engineers