Time-Temperature Superposition in Miscible Polymer Blends

1 Time-Temperature Superposition in Miscible Polymer Blends 

In the preceding chapter we discussed the application of TTS to flexible homopolymers in order to obtain generalized plots (or correlations) that may be used to estimate the 

Failure of TTS in some miscible polymer blends has also been attributed to the presence of two species whose relaxation dynamics have different temperature dependencies (Chung et al. 1994b Colby 1989). The slower relaxing component of the blend has a stronger temperature dependenee. In other words, the relaxation time of the polymer with the higher has stronger temperature dependence than the relaxation 

There is another view on the failure of TTS in some miscible polymer blends. Namely, TTS fails when the monomeric friction coefficients ( q.a o,b) th  

Information on the monomeric friction coefficients of the constituent components in a miscible polymer blend is therefore vital for a better understanding of the rheological behavior (the dynamics) of miscible blends. Efforts to obtain such information have been reported by some investigators (Composto et al. 1990, 1992 Kim et al. 1994), who employed forward recoil spectrometry to measure the reptation (tracer) diffusion coefficients of the constituent components in a miscible polymer blend. Specifically, measurements of tracer diffusion coefficient (D ) allowed them to calculate monomeric friction coefficients using the following expression, which is based on the tube model (Kim et al. 1994) 3 

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Colby, R. H., Breakdown of time-temperature superposition in miscible polymer blends. Polymer, 30, 1275-1278 (1989). 

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