INFLUENCE OF CURE SCHEDULE AND STOICHIOMETRY ON THE DYNAMIC-MECHANICAL BEHAVIOR OF TETRAFUNCTIONAL EPOXY-RESINS CURED WITH ANHYDRIDES

Epoxy networks based on N,N,N',N'-tetraglycidyl-4,4'-diamino diphenylm ethane (TGDDM) prepolymer were prepared with cis-1,2,3,6-tetrahydropht halic anhydride (THPA) curing agent at anhydride/epoxy group ratios va rying from 0.3 to 1.0. For post-cured mixtures, dynamic mechanical tes ts show that the glass transition temperature reaches the maximum valu e at stoichiometric ratios between 0.8 and 0.9. This behaviour has bee n related to the crosslink density of the formed networks, and also to etherification reactions occurring during cure which lower the amount of anhydride needed in order to complete the curing process. The stud y of cure cycle variations on the viscoelastic properties showed that for epoxy/anhydride mixtures high post-cure temperatures could be need ed to reduce the amount of unreacted epoxy groups after curing. Fourie r transform infra-red spectroscopy has been used to analyse the residu al epoxy groups and also to study the influence of the different cure reactions on the physical properties of these networks. Copyright (C) 1996 Elsevier Science Ltd.