Rheology application creep test

Four modes of characterization are of interest chemical analyses, ie, qualitative 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, flammability, creep, etc, depending on the particular application (239). 

In Section 24.1 we have defined ways of prediction of long-term behavior from short-term tests. Let us now provide more examples of application of these concepts. Creep and stress relaxation have been determined for PET/ 0.6PHB, where PET is the poly(ethylene terephthalate), PHB, the p-hydroxybenzoic acid, and 0.6 is the mole fraction of the latter in the copolymer [58]. PET/0.6PHB is a polymer liquid crystal, see chapter 41 on PECs in this Handbook. In temperature ranges of interest it forms 4 coexisting phases [60]. Conventional wisdom said that prediction methods work only for so-called rheologically simple materials, practically for one-phase polymers. Therefore, we have decided to apply as severe a test as possible to our prediction methods and a multiphase PLC is a good choice. 

Macroscopic properties, alternatively referred to as bulk properties or simply performance , are of the utmost importance in material selection. For any application it is essential that the material provides the properties desired, under the conditions of use. In addition, it is wise to characterise the material more fully in order to understand what the effect might be, for example, of changing the temperature. Consideration should also be given to time-related phenomena, such as creep or stress relaxation. What are the consequences of dimensional instability Techniques that can provide this type of information directly include mechanical testing, rheology and thermal analysis. In cases where knowledge of the relationship between structure and properties is desirable, then obviously the techniques described here must be used in combination with those which follow. 

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