Flow Imposed Morphology

Performance of polymer blends depends on the properties of polymeric components, as well as how they are arranged in space. The spatial arrangement is controlled by the thermodynamics and flow-imposed morphology. The word thermodynamics invariably brings to mind miscibility. However, thermodynamics has a broader use for the practitioners of polymer science and technology than predicting miscibility. The aim of this chapter is to describe how to measure, interpret, and predict the thermodynamic properties of polymer blends, as well as where to find the required information and/or the numerical values. 

In consequence, the flow imposed morphologies can be classified as (i) Dispersion (mechanical compatibilization), (ii) Fibrillation, (iii) Lamellae formation, (iv) Coalescence, (v) Interlayer slip, (vi) Encapsulation, etc. These types will be discussed below under appropriate headings. 

PNDB, and 5. NPDB [Utracki, 1991]. To understand the origins of this behavior, it is necessary first to evaluate morphology and flow-imposed morphology in polymer blends. 

In principle, the entire Handbook is dedicated to discussion of these three aspects. For example, in Chapter 2 on thermodynamics, the molecular aspects of polymer-polymer interactions, the methods of characterization, as well as the numerical values of the thermodynamic parameters are given. Similarly, in Chapter 3 on crystallization the three aspects vis-a-vis nucleation, melting etc. are presented. In Chapter 7 on flow, generation of flow-imposed lamellar morphology was discussed. This morphology has been used to control perme-abUity through polymeric membranes. 

It causes migration of the dispersed phase, thus imposing global changes of morphology in the formed parts, viz., skin-core structures, weld lines, blush lines, etc. In consequence, the flow-imposed morphologies can be classified as... 

The topics addressed in this book will be of interest to those working as researchers and students in doctoral or postdoctoral programs, as well as engineers they are designed to be an information source for all aspects mentioned earlier. The performance of these materials depends on the properties of different components, as well as their spatial arrangements, controlled by thermodynamics and flow-imposed morphology. In this context, the aim of this book is to describe and interpret phase morphology and interface in multiphase complex materials. 

For most blends, the morphology changes with the imposed strain. Thus, it is expected that the dynamic low strain data will not follow the pattern observed for the steady-state flow. One may formulate it more strongly in polymer blends, the material morphology and the flow behavior depend on the deformation field, thus under different flow conditions, different materials are being tested. Even if low strain dynamic data can be generalized using the t-T principle, those determined in steady state will not follow the pattern. 

Before considering the kinetics of freezing, it is worth while to say a little about the morphology of ice crystals grown in this way. This description is, unfortunately, not simple and the shapes of the crystals produced often depend more upon the heat flow conditions imposed by the experiment than upon any intrinsic properties of ice. 

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