Pseudo super-miscibility: Blends of semi-crystalline nylon pairs exhibiting a single T sub g and a single T sub 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 and characterized by Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD) techniques. The films containing up to 50-65% of the copolymer...

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Veröffentlicht in:Polymer engineering and science 1999-11, Vol.39 (11), p.2222-2232
Hauptverfasser: Khanna, Y P, Murthy, N S, Kuhn, W P, Day, E D
Format: Artikel
Sprache:eng
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Zusammenfassung: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 and characterized by Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD) techniques. The films containing up to 50-65% of the copolymer exhibited only a single melting temperature (T sub m ) corresponding to that of the pure homopolymer without any trace of the otherwise crystallizable, lower melting copolymer component. These observations are quite unusual since the binary blends of the homopolymers of nylon 6, nyloon 66, and nylon 12 exhibit their characteristic 2 T sub m 's. That result was significant in that at least 20% nylon 6 units (T sub m =222 deg C) can be incorporated into nylon 66 (T sub m =262 deg C) without any depression either in the T sub m or in the crystallinity of nylon 66 while retaining its T sub m =262 deg C as the only melting phase. Also, it has now become possible to develop blend compositions based on > =4 polyamide moieties that exhibit a single T sub g , high crystallinity, and a single T sub m corresponding to the highest melting component. We believe that the observed phenomenon, psuedo super-miscibility, is kinetically driven (i.e., only the higher melting homopolymer crystallizes), rather than thermodynamically or crystallographically, since the structural units originate from polymers that are inherently not isomorphic. In view of the unexpected observation, at least in the field of nylons and its technological significance, we anticipate renewed interest in this area and more definitive understanding to emerge from future studies.
ISSN:0032-3888