1992 Volume 41 Issue 465 Pages 821-826
Simultaneous Interpenetrating Polymer Networks (SIN's) were prepared from epoxy resin and bismaleimide (BMI) under various gelling conditions of both resins. Dynamic mechanical and tensile properties were examined as a function of a gel-time ratio (Gt) of the epoxy resin to that of BMI for the SIN's with constant content of BMI and, for comparison, as a function of concentration of BMI for the truely simultaneous IPN's. The rubbery plateau modulus considerably increased with increasing BMI content, but it was not dependent on Gt. The modulus behavior with a content of BMI followed nearly the Budiansky's and Davies's equations. On the other hand, the Tα decreased with increasing Gt at Gt>0.5, while it was nearly constant at Gt<0.5. This suggests that the faster the polymerization rate is for the BMI component compared with the epoxy resin, the less the miscibility between both components is. The tensile strength was maximum at the condition of nearly simultaneous gelation. The maximum seems to yield from the most densification of molecular packing attained by the greatest molecular mixing.
