Kinetics and rheological properties

A complete analysis of the role of the radial distributions of all the parameters that determine the flow through a tubular reactor during polymerization is a very complicated, and it is doubtful whether general solutions can be found. However, solutions can be obtained for various situations for a system with known kinetic and rheological properties, because we will be searching for specific details rather than for a general physical picture of the process. It is also possible to carry out a general analysis at certain simplified models, which nevertheless include the principal rheokinetic effects. 

Moreover, adsorption isotherms, or equations of state, represent the basis for the evaluation of adsorption kinetics and rheological properties of adsorption layers. Exact equilibrium values of surface or interfacial tensions are necessary to determine adsorption isotherms. For surfactants of low surface activity (for example, sodium octyl or decyl sulphate, hexanol or hexanoic acid) the adsorption reaches its equilibrium state in a time of the order of seconds to minutes. Higher surface activity results in greater times for establishing the equilibrium state of adsorption which sometimes cannot be realised by available experimental methods. To avoid long-time experiments, extrapolations were often carried out in order to get equilibrium values. Different extrapolation procedures as well as criteria of an equilibrium state of adsorption are discussed in the literature (cf Miller Lunkenheimer 1983). 

Oelschlaeger C, Waton G, Candau SJ, Cates ME (2002b) Structural, kinetics, and rheological properties of low ionic strength dilute solutions of a dimeric (gemini) surfactant. Langmuir 18(20) 7265-7271... 

Figure 14.1 Schematic showing the relationships between cure kinetics and rheological properties of thermoset resins.

The criteria by which these resins are evaluated include thermal analysis, cure kinetics and rheological studies of the uncured resin. Mechanical properties including hot/wet sample testing and thermal analysis are then obtained from cured neat resin speciswns. The results from these tests run on the neat resin will give some indication of the suitability of that resin for use as a composite matrix material and future studies to be conducted. 

Influences of the different methacrylates and 1,2-polybutadiene as coagents on the mechanical and rheological properties of the peroxide-cured PP/EPDM TPVs were reported by Rishi and Noordermeer [39, 40]. They interpreted the results in terms of solubility parameter and cure kinetics. The effects of coagents on both processing and properties of the compound depend on the nature of the polymer, type of peroxide, and other compounding ingredients. Among the methacrylate... 

It is beyond the scope of this review to discuss in detail viscoelastic properties at and after gelation. The gel point is one of the important characteristics in the epoxy resin curing process from both kinetic and rheological aspects. The gelation transition has been widely studied for epoxy resin systems [39,44,133-138] and already discussed in some of this series, such as by Malkin and Kulichikhin [28], Williams et al. [139], and Winter and Mours [140]. Rheological techniques for the determination of the gel point have been summarized for thermosetting resins by Halley et al. [29,141]. 

Ducel, V., Richard, J., Popineau, Y., Boury, R, 2004a. Adsorption kinetics and rheological interfacial properties of plant proteins at the oil-water interface. Biomacromolecules 5, 2088-2093. 

Ma, X., Liang, G., Liu, H., Fei, J., and Huang, Y. 2005. Novel intercalated nanocomposites of polypropylene/organic-rectorite/polyethylene-octene elastomer Rheology, crystallization kinetics, and thermal properties. Journal of Applied Polymer Science 97 1915-1921. 

Polymer colloids are useful as size standards in microscopy and in instrument calibration, and as carriers in antibody-enzyme diagnostic tests. As suspensions of uniform spherical particles, they are ideal experimental systems to test the series of colloidal phenomena as stability and coagulation, electric kinetic or rheological properties, and light scattering. In recent years, polymer colloids have received attention as models for many-body molecular phenomena, including the order-disorder transitions and the mechanics of crystalline phases. 

In real life, flocculation and coalescence can occur simultaneously with different kinetics. The rheological properties of the emulsions will vary accordingly. 

Chapter 8 starts the presentation of colloidal properties. Chapters 8 and 9 discuss the kinetic, optical and rheological properties of colloids and we illustrate how measurements on these properties can yield important information for the colloidal particles especially their molecular weight and shape. 

The change of rheological properties of reaction systems is determined by two main factors kinetic features and rheological properties of initial and forming components. To establish the conditions of gel formation during reaction, both the kinetics of reaction and the rheokinetics were studied [119,319]. Simultaneous semi-IPNs produced from cross-linked PU... 

Chemorheology is concerned with the chemical kinetics and the associated flow properties of a model reacting system. Energetic composite rheology is a continuously evolving process. The initial slurry viscosity is determined by the system temperature, plasticizer content... 

PP is probably the most thoroughly investigated system in the nanocomposite field next to nylon [127-132]. In most of the cases isotactic/syndiotactic-PP-based nanocomposites have been prepared with various clays using maleic anhydride as the compatibilizer. Sometimes maleic anhydride-grafted PP has also been used [127]. Nanocomposites have shown dramatic improvement over the pristine polymer in mechanical, rheological, thermal, and barrier properties [132-138]. Crystallization [139,140], thermodynamic behavior, and kinetic study [141] have also been done. 

Despite their flaws, batch processes have stood the test of time for a number of reasons, the most important of which is the flexibihty it brings to the manufacturer in terms of the range of products that the plant can produce, the feedstocks used to produce them, and the speed at which they can be brought to market with very limited information on physical properties, reaction kinetics, and so on (very few, if any, Michelin-starred chefs have ever measured the rheology or kinetics of their latest culinary creation). This flexibility, however, has a price which comes in the form of lower efficiencies in terms of production, energy, labor, and so on, and ultimately efficiency equates to cost However, one should never underestimate the pull of flexibility particularly, as discussed earlier in the examples of fermentation, where control of important parameters is difficult to achieve. 

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