Hexa(eugenol)cyclotriphosphazene modified bismaleimide resins with unique thermal stability and flame retardancy

We have successfully synthesized high performance bismaleimide based hexa(eugenol)cyclotriphosphazene (HECTP) resin which possess good mechanical, excellent thermal stability at high temperature and flame retardant properties. Hexa(eugenol)cyclotriphosphazene (HECTP) were obtained by the reaction of sodium, eugenol (EG) and hexachlorocyclotriphosphazene (HCCP). 1H NMR and 31P NMR were employed to confirm the formation of (HECTP). NMR analysis of the HECTP showed that all chlorine (Cl) atoms of HCCP were successfully substituted by sodium (Na) atom of the sodium eugenol. The 4,4′-bismaleimidodiphenylmethane (BMI) was reacted with EG and HECTP to produce BMI-EG1/1 resin with maleimide/allyl unit ratios of 1/1 and BMI-HECTP resins with maleimide/allyl unit ratios of 1/1, 1.5/1, 2/1, 2.5/1 and 3/1, respectively. The characterization results of TGA showed that HECTP could greatly enhance the thermal stability, the residues of BMI-HECTP 1/1, 1.5/1, 2/1, 2.5/1, 3/1 resins were 61%, 63.9%, 68%, 66.2% and 65% respectively. Besides, their flame retardancy were excellent, and the LOI values of all BMI-HECTP resins were 39%, 48.4%, 50.1%, 49.8% and 48.9% respectively, and the results of all BMI-HECTP resins at UL-94 vertical burning tests reached V-0 level and extinguished at once after removing the flame agitator. The flexural strength (77.77-100.03 MPa) of all BMI-HECTP resins was higher than that of BMI-EG1/1 (73.93 MPa). Furthermore, the impact strength of BMI-HECTP1/1, BMI-HECTP1.5/1 and BMI-HECTP 2/1 were 12.4, 13.3 and 11.94 KJ·m− 2, respectively, higher than that of BMI-EG1/1(9.42 KJ·m− 2), except for BMI-HECTP 2.5/1 (9.19 KJ·m− 2) and BMI-HECTP3/1 (6.14 KJ·m− 2).