Thermal properties of melt-blended poly(ether ether ketone) and poly(ether imide)

The thermal properties of blends of poly(ether ether ketone) (PEEK) and poly(ether imide) (PEI) prepared by screw extrusion were investigated by differential scanning calorimetry. From the thermal analysis of amorphous PEEK-PEI blends which were obtained by quenching in liquid nitrogen, a single glass transition temperature (T-g) and negative excess heat capacities of mixing were observed with the blend composition. These results indicate that there is a favorable interaction between the PEEK and PEI in the blends and that there is miscibility between the two components. From the Lu and Weiss equation and a modified equation from this work, the polymer-polymer interaction parameter (chi(12)) of the amorphous PEEK-PEI blends was calculated and found to range from -0.058 to -0.196 for the extruded blends with the compositions. The chi(12) values calculated from this work appear to be lower than the chi(12) values calculated from the Lu and Weiss equation. The chi(12) values calculated from the T-g method both ways decreased with increase of the PEI weight fraction. (C) 1999 John Wiley & Sons, Inc.