Further Rheology Studies

Aspects of viscosity, elasticity, and morphology have been discussed in general terms by various workers [73-76]. Rheological studies specific to particular polymers include dynamic rheological measurements and capillary rheometry of rubbers [77], capillary rheometry of PP [78], degradation of PP [79], torsion rheometry of PE [80], viscosity effects in blends of PC with styrene-acrylonitrile and acrylonitrile-butadiene-styrene [81], peel adhesion of rubber-based adhesives [82], and the effect of composition of melamine-formaldehyde resins on rheological properties [83]. 

Treny and B. Duperray in Proceedings of the ANTEC 97 conference, Toronto, Canada, Spring 1997, Volume HI, p.2805. 

Exstar 6000 Series, Dynamic Mechanical Spectrometer, Seiko Instruments Co. 

Foreman, J.E.K. Schawe and M. Wagner in Proceedings of the 162nd ACS Rubber Division Conference, Pittsburgh, PA, USA, Fall 2002, Paper No.l3. 

Rodriguez-Perez, S. Rodriguez-Llorente and J.A. De Saja, Polymer Engineering and Science, 1997, 37, 959. 

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Rheo-NMR [86] methods have been shown to be well-suited to emulsion rheology studies [28] and could be combined with any of the topics described above. The combination of structural and rheological measurements is a promising area for further research. 

While dynamic mechanical and steady shear measurements are frequently used in rheology studies of surfactant systems, extensional viscosity measurements are lacking. This can be attributed to the difficulties associated with such measurements and the lack of commercial laboratory instrumentation since the discontinuance of the Rheometric Scientific RFX rheometer. For many detergent compositions, the relatively low viscosity further complicates such measurements. There appear to be very few data on extensional or elongation viscosity for detergent consumer products and actives in the technical literature at this time. 

For the polymers derived by polymerization with methylamine from TADB, MADE, and DADB, respectively, rheological studies have been performed. While the TADB-based polymer exhibits viscoelastic behavior, with the viscous contribution being 10 times higher than the elastic one, the MADB-and DADB-based polymers show an almost purely viscous behavior. For the latter two polymers, the ratio of the viscous and the elastic contributions amounts to 100. Furthermore, it has been foimd that the TADB-based polymer shows a higher tendency to further crosslinking than the MADE- and DADB-based polymers [93]. 

The results of flic interfacial rheological studies on asphaltene adsorption at oil-water interfaces teach us a great deal about the behavior of asphaltenes and their role in emulsion stabili2ation. The conclusions drawn are based largely on the assumption that the rheological properties measured, namely flic elastic film modulus G are directly related to the surface excess concentration of asphaltenes. F. It is understood diat die elastic modulus actually depends on both the surface excess concenlration and the relative conformation (i.e., coimectivity) of the adsorbed asphaltenes. It is further understood that a minimum adsorbed level is required to observe a finite value of G and that the relationship between G and G is not linear. With these caveats in mind, we can conclude die following ... 

Let us further utilize the literature values of V, /, d and the contact cohesive forces [39-43]. The length / of softwood and hardwood fibers used in the experimental studies was 1-2 mm and 20 un, respectively. The consislaicy of the pulp susp sions was 1% and 2%. The experimental rheological studies conducted in the elastic aftereffect regime were performed with the constant shear stress ranging between 10 and 90 Pa. From the experimental data for 2% softwood pulp 1 = 2 mm), the shear rate... 

Recently, numerous research groups have shown that nanofillers can have dramatic effects on the morphology and properties of either rubber- or thermoplastic-modified epoxy systems [92-95]. Although such rheology studies are still in progress, it is expected that any differences in viscoelastic behavior would further influence the phase separation process, and so have serious effects on the rheological behavior. 

The study of flow and elasticity dates to antiquity. Practical rheology existed for centuries before Hooke and Newton proposed the basic laws of elastic response and simple viscous flow, respectively, in the seventeenth century. Further advances in understanding came in the mid-nineteenth century with models for viscous flow in round tubes. The introduction of the first practical rotational viscometer by Couette in 1890 (1,2) was another milestone. 

Tubular membranes of 8 long were prepared from blend composition consisting of CA and PMMA and performance data for one month operation was collected. These datas show high product water flux (18-20 gfd.) with low flux decline slope. However, it was observed that these membranes initially showed fountains" which disappeared in about 30 minutes time. This was attributed to the peculiar membrane rheology and orientation of PMMA molecule with respect to CA molecule. This needed further study for confirmation. 

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