Pseudo super-miscibility: Blends of semi-crystalline nylon pairs exhibiting a single T-g and a single T-m

Physical blends of nylon 6 (or nylon 66) homopolymer with random copolymers of nylon 6/nylon 66 or of nylon 6/nylon 12 were melt extruded into films a nd characterized by Differential Scanning Calorimetry (DSC) and X-ray Diffr action (XRD) techniques. The films containing up to 50-65% of the copolymer exhibited only a single melting temperature (T-m) corresponding to that of the pure homopolymer without any trace of the otherwise crystallizable, lo wer melting copolymer component. These observations are quite unusual since the binary blends of the homopolymers of nylon 6, nylon 66, and nylon 12 e xhibit their characteristic 2 T-m's. That result was significant in that at least 20% nylon 6 units (T-m = 222 degrees C) can be incorporated into nyl on 66 (T-m = 262 degrees C) without any depression either in the T-m or in the crystallinity of nylon 66 while retaining its T-m = 262 degrees C as th e only melting phase. Also, it has now become possible to develop blend com positions based on greater than or equal to 4 polyamide moieties that exhib it a single T-g, high crystallinity, and a single T-m corresponding to the highest melting component. We believe that; the observed phenomenon, pseudo super-miscibility, is kinetically driven (i.e., only the higher melting ho mopolymer crystallizes), rather than thermodynamically or crystallographica lly, since the structural units originate from polymers that: are inherentl y not isomorphic. In view of the unexpected observation, at least in the fi eld of nylons and its technological significance, we anticipate renewed int erest in this area and more definitive understanding to emerge from future studies.