DIELECTRIC AND THERMALLY STIMULATED DISCHARGE CURRENT STUDIES OF RUBBER-MODIFIED EPOXY-RESINS

Comparison is drawn between data obtained from dielectric relaxation a nd thermally stimulated discharge current (TSDC) measurements on blend s of carboxyl-terminated butadiene acrylonitrile (CTBN) with an epoxy resin (ER) obtained by reaction of the diglycidyl ether of bisphenol A (DGEBA) with either triethylenetetramine (TETA) or diaminodiphenylmet hane (DDM). The effect of varying the composition of CTBN on the natur e of the phase separation was examined using electron microscopy and w as also evident from changes in the dielectric spectrum and the calcul ated activation energy for the molecular relaxation process. The morph ology consists of spherical rubber particles dispersed in an epoxy mat rix at low levels of CTBN, and at higher concentrations epoxy resin is observed to be precipitated as spheres within the rubbery phase. Deta iled analysis of the dipolar spectra indicates that at low concentrati ons there appears to be some cosolution of the epoxy in the CTBN.