Class transition and miscibility in blends of two semicrystalline polymers: Poly(aryl ether ketone) and poly(ether ether ketone)

Binary melt-blended mixtures of two aryl ether ketone polymers (i.e., a new polyaryl ether ketone) (code name PK99) and poly(ether ether ketone) (PEEK ), have been studied. Polymer miscibility in glassy amorphous (or melt) dom ains has been demonstrated for the binary blend comprising of two aryl-ethe r-ketone-type semicrystalline polymers. Composition-dependent, single T-g w as observed within full composition range in the PK99/PEEK blends, and the narrow T-g breadth also suggests that the scale of mixing was fine and unif orm. To better resolve any possible overlapping T-g's, physical aging was i mposed on a comparison set of blend samples for the purpose of improving de tectability of overlapped multiple transitions if existing. The result stil l showed one single T-g. The relative sharp T-g and lack of cloud point tra nsition suggest that the scale of molecular intermixing is good. Phase homo geneity was further confirmed using optical and scanning electron microscop y. The X-ray diffractograms suggest that isomorphism does not exist in the PK99/PEEK blends and that the crystal forms of the respective polymers rema in distinct and unchanged by the miscibility in the amorphous region. (C) 1 999 John Wiley & Sons, Inc.