Synthesis, characterization, curing and thermal studies of phosphorylated epoxy resins

Abstract

Phosphorous containing two epoxies tris (glycidyloxy) phosphine oxide (TGPO) and tris (glycidyloxy) phosphine (TGP) are synthesized and their structure are characterized with the help of FTIR, ¹HNMR, ¹³CNMR, and ³¹PNMR spectroscopy. Synthesized TGPO/TGP is blended with DGEBA, which after curing with diamine curing agents, viz., 1,4-phenylene diamine (P), 3,4’-oxydianiline (O), 4,4’-diaminodiphenyl sulphide (DS), and 1,5-diamino naphthalene (N) resulted in several phosophorylated epoxy polymers. Curing reactions and reactivities of polymers are studied via DSC, which revealed that TGP is relatively more reactive towards diamine curing agent than TGPO. Further, among the diamines phenylene diamine (P) is most reactive curing agent towards both the epoxies as compared to other diamines. Thermal gravimetric analysis (TGA) was used to study the thermal behaviour and weight loss behaviour of cured epoxy resin. The phosphorous containing epoxy resin shows lower weight loss temperature and higher char yield (~23-36) and LOI (~27-32) values than that of Bisphenol-A based epoxy resin (char yield~10-12 & LOI~21-22), which confirms the effectiveness of phosphorylated epoxy resins as flame retardant.