Polymer rheology relaxation time

Earlier studies [14,15] clearly reveal that there is a reaction between two polymers and that the extent of reaction depends on the blend ratio. As 50 50 ratio has been found to the optimum (from rheological and infrared studies) ratio for interchain crosslinking, the higher heat of reaction for the NBR-rich blend may be attributed to the cyclization of NBR at higher temperatures. There is an inflection point at 50 50 ratio where maximum interchain crosslinking is expected. Higher viscosity, relaxation time, and stored elastic energy are observed in the preheated blends. A maximum 50-60% of Hypalon in NBR is supposed to be an optimum ratio so far as processibility is concerned. 

Lodge, A. S., Wu, Y.-J. Exact relaxation times and dynamic functions for dilute polymer solutions from the bead/spring model of Rouse and Zimm, Report 16. Rheology Research Center, University of Wisconsin (July, 1972). 

One convenient strategy to interpret these results is to review the molecular characteristics of binary blends as extracted from polymer melt rheology [40]. The influence of short chains (M < Me) is to effectively decrease the plateau modulus and the terminal relaxation times as compared to the pure polymer. Consequently, the molecular weight between entanglements... 

Wissbrun earlier observed a very long relaxation time and high elasticity for anisotropic melts of aromatic polyesters, as well as several other types of flow anomalies. Unfortunately, in most of these earlier studies, the rheological behavior of liquid crystal melts of polymers could not be directly compared with that of the isotropic phase of the same polymers because of their high clearing temperatures. 

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