Chemorheology and ultimate behavior of epoxy-amine mixtures modified with a liquid oligomer

Rubber toughening of epoxy resins has been actively studied since the 1960s with clear progress in understanding of the ultimate properties: microstru cture relationships. The morphology, obtained after curing of the modified thermosetting matrix, is a function of the process conditions as well as of the materials used because both influence the thermodynamics and the kinet ics of phase separation. In this work several amounts of poly(oxypropylentr iamine) (POPTA), have been added as modifier to a diglycidyl ether of bisph enol-A (DGEBA)-based epoxy matrix cui ed with a cycloaliphatic amine. Molec ular weight of the neat resin and amine/epoxy stoichiometric ratio have als o been used as variables. This investigation has focused upon the importanc e of cure chemorheology for microstructure formation by using both physicoc hemical (isothermal and dynamic calorimetry) and rheological techniques. In the second part of this study, the influence of the molecular weight of th e epoxy resin in the ultimate properties of 15 wt % POPTA-modified epoxy ma trices is also analyzed. (C) 2000 John Wiley & Sons, Inc.