Mechanical and rheological testing

Mechanical and rheological testing of polymers or polymer compounds needs to be carried out for a number of reasons. These include  

Monitoring the quality and consistency of raw materials and products made from these. 

Establishing the suitability of a particular design to the application. Determining some estimate of service life under typical conditions. 

It should always be remembered that no matter how far-sighted the test designer, test results can never predict precisely how a polymer compound may process or meet service requirements. Despite these limitations, some form of testing will be required in vk tually all polymer applications. 

Polymer materials behave in many respects in a different manner from more conventional materials like metals and ceramics. Thus, although certain tests, like tensile-strength, hardness and impact, can be similar to those employed with metals, many of the tests used in the polymer industry are specific to polymers. 

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M. Flanagan, Mechanical and rheological testing. In B.J. Hunt and M.I. James (Eds.), Polymer Characterisation, Blackie Academic and Professional, Glasgow, 1993, pp. 261-296 Chapter 9. 

Since sensory and mechanical properties of a food depend on its microstructure, the knowledge of microstructure must precede any operation aimed to the attainment of a specific texture (Ding and Gunasekaran, 1998). The instrumental measurements of mechanical and rheological properties represent the food responses to the forces acting on the food structure and, for this reason, are affected by the way in which these analyses are performed. Furthermore, mechanical and rheological tests are always destructive and make impossible the execution of other analyses. 

Certain phenomenological relationships exist between the temperature and rate dependences of the behavior of a material in mechanical and rheological tests. A very familiar example is the time-temperature superposition principle [46] which often holds. Consequently, similar curves can also be drawn for the failure stresses as functions of strain rate. For example, ay increases... 

To achieve typical flame retardancy for cables required by the most important international cable fire test (lEC 60332-3-24, Tests on electrical cables imder fire conditions - Part 3-24 Test for vertical flame spread of vertically-mounted bunched wires or cables) demands a high loading of a mineral FR filler such as ATH. 65wt% of ATH with 35% of a suitable polymer like EVA must often be used for cable jackets. A similar compound of EVA (with 28% VA content) with ATH and 5% of a nanocomposite can pass the same test. It was found that the ATH could be reduced to only 45% of the composition. The reduction in the total amount of the fillers results in improved mechanical and rheological properties of typical EVA-based cable compoimds. The char formed is... 

Therefore, for quality control of composites or film-forming mechanisms, many tests like mechanical and rheological characteristics, thermal properties, biodegradability, etc., are necessary [48,49]. 

The rheological properties of the material are connected with these physicochemical states. In recent years significant advances have been made in both the theory of viscoelasticity and the related instrumentation. In particular dynamic, mechanical and thermal testing have become quite popular after successful applications to the analysis of polymer systems [26], some elements of which are given in the Appendix A3. 

Four modes of characterization are of interest chemical analyses, ie, quaUtative and quantitative analyses of all components mechanical characterization, ie, tensile and impact testing morphology of the mbber phase and rheology at a range of shear rates. Other properties measured are stress crack resistance, heat distortion temperatures, flammabiUty, creep, etc, depending on the particular appHcation (239). 

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