Thermosetting epoxy resin system: Ring-opening by copolymerization of epoxide with D,L-Lactide

We examined the ring-opening copolymerization of glycidyl phenyl ether (GPE) and D,L-lactide (LAC) to afford poly(GPE-co-LAC) as a model reaction of the LAC-mediated thermal curing of epoxy resins such as 2,2-bis(4-glycidyloxyphenyl)propane (BGP), 2,2-bis(4-glycidyloxyphenyl)methane (BGM), 3,3'5,5';-tetramethyl-4,4'-diglyci-dyloxybiphenyl (TDP), N,N-diglycidyl-4-glycidyloxyaniline (DGA), and oligo phenols (NC-3000 and EPPN502H). The reaction of GPE and LAC proceeded efficiently in the presence of 1,8-diazabicyclo[5.4.0]undec-7ene (DBU) at 180 ? for 2 h. The monomer reactivities r1 of LAC and r(2) of GPE calculated according to the Fineman-Ross method and the Kelen-Tudos method were 0.85 and 1.26, respectively. The relatively small difference between these values suggests that the produced poly(GPE-co-LAC) would be a gradient copolymer, different from a block copolymer or random copolymer. Based on these results, we examined the thermal curing reactions of epoxy resins BGP, BGM, TDP, DGA, NC-3000, and EPPN-502H in bulk under the same conditions. The corresponding cured products were obtained quantitatively. The thermal stability of BGP, BGM, DGA, and EPPN-502H was increased by the addition of a small amount of LAC, suggesting that the cross-linking density of the cured products was increased. This new class of thermal curing system should be applicable to epoxy resins used in various industrial applications.

Automated summary

This study investigates a new thermal curing system for epoxy resins by examining the ring-opening copolymerization of glycidyl phenyl ether (GPE) and D,L-lactide (LAC). The results suggest that the produced poly(GPE-co-LAC) is a gradient copolymer with improved thermal stability and increased cross-linking density. This new system shows potential for various industrial applications.