Dynamic rheological analysis, polymers

Huang, Y. Gelling temperatures of high acyl gellan as affected by monovalent and divalent cations with dynamic rheological analysis. Carbohydr. Polym. 56 (2004) 27-33. 

Cai, H., Ait-Kadi, A., and Brisson, J. (2003) Dynamic rheological analysis of a miscible blend showing strong interaction. Polymer, 44 (5), 1481-1489. 

The effect of oxidative irradiation on mechanical properties on the foams of E-plastomers has been investigated. In this study, stress relaxation and dynamic rheological experiments are used to probe the effects of oxidative irradiation on the stmcture and final properties of these polymeric foams. Experiments conducted on irradiated E-plastomer (octene comonomer) foams of two different densities reveal significantly different behavior. Gamma irradiation of the lighter foam causes stmctural degradation due to chain scission reactions. This is manifested in faster stress-relaxation rates and lower values of elastic modulus and gel fraction in the irradiated samples. The incorporation of O2 into the polymer backbone, verified by IR analysis, conftrms the hypothesis of... 

Measurement of viscoelastic and rheological properties of polymers are of increasing importance and recently developed instrumentation for measuring these properties discussed in Chapter 15 includes dynamic mechanical analysis, thermo-mechanical analysis... 

Some of the viscoelastic and rheological properties of polymers that can be measured by dynamic mechanical analysis are [90-92]... 

Rosalina I, Bhattacharaya M. Dynamic rheological measurements and analysis of starch gels. Carbohydr Polym 2002 48 191-202. 

Dynamic mechanical analysis in polymeric multiphase systems in solid state, as part of rheology, is associated with oscillatory tests that are employed to investigate all kinds of viscoelastic material from the point of view of flow and deformation behavior. In particular, it evaluates the molecular mobility in polymers, the pattern of which may be an indication of phase-separated systems. Although there are certain preferred tools for visual examination of phenomena for these kinds of systems, dynamic mechanical analysis has the advantage of examination in dynamic conditions and of the prediction of properties. 

Polymers are viscoelastic materials, whose mechanical behavior exhibits characteristics of both solids and liquids. Thermal analysts are frequently called on to measure the mechanical properties of polymers for a number of purposes. Of the different methods for viscoelastic property characterization, dynamic mechanical techniques are the most popular, since they are readily adapted for studies of both polymeric solids and liquids. They are often referred to collectively as dynamic mechanical analysis (DMA). Thermal analysts often refer to the DMA measurements on liquids as rheology measurements. 

An important means of assessing the rheological behavior of polymer melts and concentrated solutions is the use of dynamic mechanical analysis. This consists in testing the mechanical response, or strain, of a polymeric material to a time-dependent stress, or, conversely, measuring the stresses generated by time-dependent strains. For simplicity, a... 

The term viscoelasticity combines viscous and elastic stress-strain flow characteristics. If materials behavior is dominated by viscous flow it is generally referred to as a fluid, whereas if the elastic properties dominate the mechanical properties of a material it is considered to be solid. Most adhesives are applied in a liquid or pasty condition to allow wetting and promote spreading and then are required to phase change into a solid. In the liquid state, rheology provides the methods to differentiate between elastic and viscous flow characteristics while, for example, dynamic mechanical analysis of cured adhesive polymers uses similar principles to access elastic and viscous parameters of the stress-strain response. 

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