The rheological behavior of polyetheretherketone (PEEK) polyetherimide (PEI) blends

A study on the rheological behavior at high shear rates of PEEK/PEI blends has been performed by means of a capillary viscometer at two temperatures (350 and 370 degrees C). PEEK (polyetheretherketone) is a tough semicrystalline polymer with properties that make it very attractive for use as a high-quality engineering thermoplastic. It has been melt-blended with amorphous PEI (polyetherimide), another high-performance polymer. From previous studies it was known that PEEK/PEI blends are miscible over the whole composition range. A hoped-for enhancement in processability has been achieved only with a medium content of PEI and at a higher temperature. Finally, a phenomenological equation (Cross equation) has been used to correlate the experimental viscosity values and to predict the rheological behavior of the PEEK/PEI blends even at very low shear rates. The model has been found to fit all the experimental data well at both 350 and 370 degrees C.