EFFECT OF PREREACTION ON CURING OF ELASTOMER-MODIFIED EPOXY-RESINS

Three multifunctional epoxy resins novolac epoxy (EPN), triglycidyl pa raaminophenol (TGPAP), and tetraglycidyl diaminodiphenylmethane (TGDDM ) were modified with a carboxy-terminated acrylate-based liquid elasto mer (PnBA). The effect of prereaction of the epoxy groups in the resin and carboxyl group in the elastomer on curing parameters, such as the cure reaction conversions; processing parameters, such as gel times a nd vetrification times; initial cure temperatures, and activation ener gy values were evaluated. Fourier transform infrared spectrometry (FTI R), dynamic mechanical spectrometry (DMS), and differential scanning c alorimetry (DSC) were used for the study. The results indicated that w hile the cure reactions were slightly retarded in the presence of elas tomer, they were slightly accelerated when certain prereaction catalys ts were used. The gel times and vitrification times decreased due to t he prereaction. The physical properties such as fracture toughness and modulus of neat resin castings and flexural strength properties of ca rbon cloth-reinforced laminates were evaluated. Results indicated that the toughness property increased and the modulus decreased with elast omer addition. (C) 1997 John Wiley & Sons, Inc.