Amorphous time-temperature superposition process

For semi-crystalline polymers with melting points of more than 100 °C above the glass transition temperature and for amorphous polymers far above the glass transition temperature Tg (at around T = Tg + 190°C), the shift factors obtained from time-temperature superposition can be plotted in the form of an Arrhenius plot for thermally activated processes ... 

The calculation of residual stresses in the polymerization process during the formation of an amorphous material was formulated earlier.12 The theory was based on a model of a linear viscoelastic material with properties dependent on temperature T and the degree of conversion p. In this model the effect of the degree of conversion was treated by a new "polymerization-time" superposition method, which is analogous to the temperature-time superposition discussed earlier. 

In the preceding sections, we have looked at the various types of relaxation processes that occur in polymers, focusing predominantly on properties like stress relaxation and creep compliance in amorphous polymers. We have also seen that there is an equivalence between time (or frequency) and temperature behavior. In fact this relationship can be expressed formally in terms of a superposition principle. In the next few paragraphs we will consider this in more detail. First, keep in mind that there are a number of relaxation processes in polymers whose temperature dependence we should explore. These include ... 

In amorphous polymers, this relation is valid for proeesses that extend over very different length scales. Modes which involved a few monomer imits as well as terminal relaxation processes, in whieh the chains move as a whole, obey the superposition relaxation. On the basis of this finding an empirieal expression for the temperature dependence of viscosity at a zero shear rate and that of the mean relaxation time of a modes were derived ... 

In immiscible blends, the t-T principle does not hold. Eor immiscible amorphous blends it was postulated that two processes must be taken into account the t-T superposition, and the aging time [Maurer et al, 1985]. On the other hand, in immiscible blends, at the test temperature, the polymeric components are at different distance... 

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