Thermoplastic elastomer gels. II. Effects of composition and temperature on morphology and gel rheology

✍ Scribed by J. H. Laurer; J. F. Mulling; S. A. Khan; R. J. Spontak; J. S. Lin; R. Bukovnik

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 389 KB
• Volume: 36
• Category: Article
• ISSN: 0887-6266
• DOI: 10.1002/(sici)1099-0488(199810)36:14<2513::aid-polb5>3.0.co;2-t

✦ Synopsis

Thermoplastic elastomer gels (TPEGs) composed of a poly[styrene-b-{ethylene-co-butylene)-b-styrene] triblock copolymer and a low-volatility, midblock-compatible mineral oil have been investigated here to ascertain the effects of composition on TPEG morphology, and temperature on mechanical properties. Cryofracture-replication transmission electron micrographs reveal the existence of spheroidal bumps due to copolymer micelles, as well as a network of irregularly shaped, high-aspect-ratio features. Since the density of this network decreases with increasing oil concentration, these features are attributed to copolymer grain boundaries. Micellar periodicities are discerned from small-angle X-ray scattering as a function of copolymer concentration and compared with previously reported data from related systems. Dynamic rheological tests performed up to 140°C indicate that the linear viscoelastic regime for these TPEGs decreases with both increasing copolymer concentration and temperature. A concentration-dependent thermal transition, signified by an abrupt reduction in the dynamic elastic modulus (GЈ), has also been identified.