STUDIES ON THE THERMAL AND CURING BEHAVIOR OF POLYIMIDE BLENDS

Blends of thermosetting (Thermid MC-600 and Thermid FA-700) and thermoplastic (ULTEM 1000) polyimide resins with different compositions were prepared. Curing and thermal behavior of the blends were investigated using differential scanning calorimetry and dynamic thermogravimetry in a nitrogen atmosphere. The peak exotherm temperature increased with increasing amount of thermoplastic resin, whereas the heat of polymerization decreased. The electrical characteristics of the blends were also investigated using a dielectric analyzer. Dynamic as well as isothermal scans were recorded. Ionic conductivity, permittivity, and the loss factor were measured as a function of temperature at various frequencies. These results showed the complete curing of the resins having 50% Ultem at 225-degrees-C in 1 h, whereas Thermid MC-600 required a postcuring step to observe fully cured resins. A marginal decrease in thermal stability was observed on blending. (C) 1994 John Wiley & Sons, Inc.