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

Abstract

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 (G′), has also been identified.© 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2513–2523, 1998

Dispersion of multiwalled carbon nanotubes in thermoplastic elastomer gels: Morphological, rheological, and electrical properties

“…Comparable behavior was observed in the TPEGs with 20% SEBS (Fig. 6b) concentration suggesting that just below this temperature, the gel network reinforcing TPEGs undergoes some of supramolecular rearrangement, perharps similar to an order-disorder transition (ODT) [12].…”

“…While numerous fundamental studies on the rheological and morphological properties of molecular networks composed of a microphase-separated multiblock copolymer swollen to a large extent by a low-volatility midblockselective solvent, [11][12][13][14][15] few comparable efforts have extended studies to thermoplastic elastomer gels in the presence of multiwalled carbon nanotubes (MWCNTs). The aim of this article is to determine the effect of MWCNTs on the rheological, thermal, mechanical and morphological properties of NCTPEGs from microphaseordered poly(styrene-b-(etheylene-co-butylene)-b-styrene (SEBS) dissolved in hydrocarbon oil properties.…”

Design of lubricating grease formulations using recycled polypropylene from postconsumer films as thickener agent

“…This behavior with the temperature is similar to that shown by traditional lithium lubricating greases previously studied 20 and as, in the case of other copolymers, the ability of the polyolefin to form physical networks can explain the gel-like mechanical behavior shown by these materials over a wide range of temperature and frequencies. 21,22 These samples are not thermorheologically simple materials and, therefore, it was not possible to apply the time-temperature superposition principle to the experimental linear viscoelasticity data. 17 This fact may be due to the development of multiphase domains depending on the temperature and polymer concentration.…”

Influence of Morphology and Rheological Properties on the Mechanical and Dielectric Behavior of Block Copolymer Gels

“…The MO used (Dinâmica Química) has a density of 0.842 g cm À3 , and it acts as a selective solvent to the PEB midblocks, since it is only miscible with PEB and not with PS. [15,16,30,31] The samples were obtained by solution casting, using toluene as the solvent. The solutions were prepared by magnetic stirring at 60 C, using a polymer/solvent ratio of 0.2 g mL.…”