Chemical modification of matrix Resin networks with engineering thermoplastics

Summary

Functionally terminated bisphenol-A polysulfone oligomers were used in the modification of Epon Resin 828/4,4′-diamino-diphenylsulfone (DDS) network system. Phenolic hydroxyl terminated PSF oligomers were first capped with a large excess of bisphenol-A diglycidyl ether or Epon Resin 828 at both ends and then the resulting system was cured with DDS, in a two-step process. During these studies molecular weight and the amount of PSF oligomers incorporated into the network were varied and their effect on the overall properties of the resulting systems were investigated. The capping and curing reactions were followed by using FT-IR and NMR spectroscopy, GPC, HPLC and DSC techniques. As a function of the oligomer molecular weight, SEM studies showed the formation of two-phase structures with ductile PSF particles dispersed in the continuous epoxy matrix. Mechanical characterization and fracture toughness measurements showed a remarkable increase in K_IC or g_IC values of the modified networks over that of control, without significant loss in the modulus. This work would appear to be one of the first studies where well bonded ductile glassy modifiers have significantly improved the fracture toughness of highly crosslinked networks.