Copolymers rheology

Fig. 8. Load (P) versus load-line displacement (8) of the copolymer, EPBCO, and controUed-rheology copolymers, EPBC-CRIOI, EPBC-CR332 and EPBC-CR471...

The fractographic analysis carried out via scanning electron microscopy on EPBCO-2 showed the same micromechanism of failure as that described for the controlled-rheology copolymers, that is, macroductile tearing formed by broken stretched filaments oriented in the direction perpendicular to the crack propagation (Fig. 17). However, the ductile tearing... 

Table 2. Rheological and Physical Properties of EMAA Copolymers, ...

Block (Star) Arrangement. The known star polymers, like their linear counterparts, exhibit microphase separation. In general, they exhibit higher viscosities in the melt than their analogous linear materials. Their rheological behavior is reminiscent of network materials rather than linear block copolymers (58). Although they have been used as compatibiUzers in polymer blends, they are not as effective at property enhancements as linear diblocks... 

An indication of whether block or copolymer architecture is AB, ABA, or ( AB ) n often be seen in its rheological behavior. For example,... 

Optical and electro-optical behavior of side-chain liquid crystalline polymers are described 350-351>. The effect of flexible siloxane spacers on the phase properties and electric field effects were determined. Rheological properties of siloxane containing liquid crystalline side-chain polymers were studied as a function of shear rate and temperature 352). The effect of cooling rate on the alignment of a siloxane based side-chain liquid crystalline copolymer was investigated 353). It was shown that the dielectric relaxation behavior of the polymers varied in a systematic manner with the rate at which the material was cooled from its isotropic phase. 

Veenstra H., Hoogvfiet R.M., Norder B., De B., and Abe P. Microphase separation and rheology of a semicrystalUne poly(ether-ester) multiblock copolymer, J. Polym. Sci. B. Polym Phys., 36, 1795, 1998. Garbrieelse W., SoUman M., and Dijkstra K., Microstmcture and phase behaviour of block copolyfether ester) thermoplastic elastomers. Macromolecules, 34, 1685, 2001. 

Antony, P., Puskas, J.E., and Kontopoulou, M. The Rheological and Mechanical Properties of Blends Based on Polystyrene-Polyisobutylene-Polystyrene Triblock Copolymer and Polystyrene. Proceedings of MODEST, International Symposium on Polymer Modification, Degradation and Stabilization, Budapest, Hungary, 2002. 

Short fiber reinforcement of TPEs has recently opened up a new era in the field of polymer technology. Vajrasthira et al. [22] studied the fiber-matrix interactions in short aramid fiber-reinforced thermoplastic polyurethane (TPU) composites. Campbell and Goettler [23] reported the reinforcement of TPE matrix by Santoweb fibers, whereas Akhtar et al. [24] reported the reinforcement of a TPE matrix by short silk fiber. The reinforcement of thermoplastic co-polyester and TPU by short aramid fiber was reported by Watson and Prances [25]. Roy and coworkers [26-28] studied the rheological, hysteresis, mechanical, and dynamic mechanical behavior of short carbon fiber-filled styrene-isoprene-styrene (SIS) block copolymers and TPEs derived from NR and high-density polyethylene (HOPE) blends. 

Clay hllers were surface modihed with TMPTA or triethoxyvinyl silane (TEVS) followed by EB irradiation by Ray and Bhowmick [394]. Both the untreated and treated fillers were incorporated in an ethylene-octene copolymer. Mechanical, dynamic mechanical, and rheological properties of the EB-cured unfilled and filled composites were studied and a significant improvement in tensile strength, elongation at break, modulus, and tear strength was observed in the case of surface-treated clay-filled vulcanizates. Dynamic mechanical studies conducted on these systems support the above findings. 

Hvidt, S Jorgensen, EB Brown, W Schillen, K, Micellization and Gelation of Aqueous Solutions of a Triblock Copolymer Studied by Rheological Techniques and Scanning Calorimetry, Journal of Physical Chemistry 98, 12320, 1994. 

Hong, B. K. and Jo, W. H. (2000) Effects of molecular weight of SEBS triblock copolymer on the morphology, impact strength, and rheological property of syndiotactic polystyrene/ ethylene-propylene rubber blends. Polymer, 41, 2069-2079. 

Associative copolymers of acrylamide with N-alkylacrylamides, terpoly-mers of acrylamide, N-decylacrylamide, and sodium-2-acrylamido-2-methyl-propane sulfonate (NaAMPS), sodium acrylate (NaA), or sodium-3-acrylamido-3-methylbutanoate (NaAMB) have been shown to possess the required rheologic behavior to be suitable for enhanced oil-recovery processes [1184]. 

A mixture of sulfonated styrene-maleic anhydride copolymer and polymers prepared from acrylic acid or acrylamide and their derivatives [759] are dispersants for drilling fluids. The rheologic characteristics of aqueous well drilling fluids are enhanced by incorporating into the fluids small amounts of sulfonated styrene-itaconic acid copolymers [761] and an acrylic acid or acrylamide polymer [755]. 

R. C. Portnoy. Anionic copolymers for improved control of drilling fluid rheology. Patent GB 2174402, 1986. 

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