Synthesis of Hyperbranched Flame Retardants with Varied Branched Chains' Rigidity and Performance of Modified Epoxy Resins

To overcome the high flammability and brittleness of epoxy resins without sacrificing their glass transition temperature (T-g) and mechanical properties, three epoxy-terminated hyperbranched flame retardants (EHBFRs) with a rigid central core and different branches, named EHBFR-HB, EHBFR-HCM, and EHBFR-HBM, were synthesized. After chemical structure characterization, the synthesized EHBFRs were introduced into the diglycidyl ether of bisphenol A (DGEBA) and cured with 4, 4-diaminodiphenylmethane (DDM). The compatibility, thermal stability, mechanical properties, and flame retardancy of the resultant resins were evaluated. Results showed that all three EHBFRs could significantly improve the fire safety of cured resins, and 30 wt. % of EHBFRs (less than 1.0 wt. % phosphorus content) endowed cured DGEBA with a UL-94 V-0 rating. In addition, the increased rigidity of branches in EHBFRs could increase the flexural strength and modulus of cured resins, and the branches with appropriate rigidity were also beneficial for improving their room temperature impact strength and T-g.

Automated summary

In order to improve the fire safety and mechanical properties of epoxy resins, researchers synthesized three epoxy-terminated hyperbranched flame retardants (EHBFRs) with different branches. These EHBFRs were added to the diglycidyl ether of bisphenol A (DGEBA) and cured with 4, 4-diaminodiphenylmethane (DDM). The results showed that the EHBFRs greatly enhanced the fire safety of the cured resins and improved their mechanical properties.