Rheology and Processing of Polymer Blends

The prediction of conductivity, a (electrical, ionic or proton), based on pure component values for miscible and phase separated systems can employ the same models as used for modulus and permeability, where a (S/cm) can be substituted for modulus (E) or permeability (P) in the log additivity relationship for miscible systems and the parallel model, series model or equivalent box model for phase separated systems. While these expressions have not been generally employed for conductivity modeling, the principles on which they are based are analogous to modulus and permeability values. 

Except for a brief review of the basic concepts of viscosity, steady shear flow and dynamic flow, the details of rheological measurements and analysis wiU be left to the noted references. 

Viscosity, q, is defined as the ratio of stress, a, and shear rate, Y n = JlY 

Two other variables derivable from tensor analysis are the first normal stress, Ni, and the second normal stress, N2, which are related to the parameters often noted in polymer rheology studies, T [, and the first and second normal stress coefficients defined as 

Miscible blends will be expected to exhibit rheological behavior similar to single component polymers. One of the simplest equations applied to miscible systems involves the relationship  

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Manchado M. A. L., Biagiotti J. and Kenny J. M., Rheological behavior and processability of polypropylene blends with rubber ethylene propylene diene terpolymer. J. Appl. Polym. Sci. 81 (2001) pp. 1-10. 

Leszek A. Utracki was bom and educated in Poland. After completing his postdoctorate at USC in Los Angeles with Robert Simha, he settled in Canada. He was a passionate researcher in the fields of thermodynamics, rheology, and processing of multicomponent/multiphase polymeric systems. Sadly, he passed away a few months after embarking on the work for the second edition of the Polymer Blends Handbook, during which he had made important contributions to the work. This edition of the handbook is dedicated to his memory. 

Collyer, A.A., The morphology and rheology of Uquid crystal polymer blends Chap 6 Rheology and Processing of Liquid Crystal Polymers (ISBN 9780412596407) D.A. Ademo, A.A. Collyer (eds), pp. 86-134, Books Express, (Saffron Walden, ESS, United Kingdom) (1996). 

This chapter focuses on recent developments in rheological and mechanical examinations of TLCP blends. Although most of the data presented are taken from actual works done at the Institute of Polymers and Processing of Zhejiang University, Hangzhou, China, this is merely a matter of accessibility and in no way implies that this data is the best or only data of this nature available. 

This chapter provides an overview of current researches on liquid crystalline polymers (LCPs). Topics include syntheses of main-chain and side-chain LCFs, structured characterization of LCFs and LCP networks and rheology and processing. Applications of LCP/polymer blends as self-reinforced polymers and electro-optical meterials are also discussed. 

An area that will require attention in the future involves in-line analysis of polymer blends during processing potentially allowing feedback information to improve uniformity of the resultant blend. In-line morphology determination, rheological measurements, and shear-induced phase behavior are subjects for consideration. Rheo-optical studies under shear for low molecular weight PS/PIB blends near phase separation conditions were... 

TLCP/isotropic polymer blends. Ironically, many rheological and processing behaviors of TLCPs are opposite to what is expected from ordinary thermoplastics. All these unusual behaviors of LCPs are not well understood. In this section, some processing behaviors of TLCPs, their morphologies, and their mechanical properties in relation to the processing conditions will be reviewed. 

The shear viscosity in polymer melts and solutions has been investigated for more than a half century. The blending process of polymers is generally performed in the molten state, particularly in shear flow. It is thus necessary to understand the flow (or better rheological) characteristics of polymer melts [66-70]. In both reactive and non-reactive blends, the shear viscosity of each polymer, and thus viscosity ratio, and bulk viscosity of polymer blend system needs to be understood. 

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