Morphology polymeric systems

The application of a flow field has pronounced effects on the crystallization dynamics and semi-crystalline morphology of polymeric systems. Under quiescent, no-flow conditions the crystallization dynamics is governed by the temperature, T, and spherulites are formed. In the presence of flow, increasing the flow rate can result in an increase of the nuclei density up to factors of 106, but the morphology remains spherulitic [18]. At even higher flow rates the so-called shish-kebab morphology is observed. This results from the de-... 

Throughout the history of polymer science there have been efforts to improve (increase) the Tg to increase the useful operating temperature range of polymers. The preponderance of the literature has concentrated on mechanically blended polymeric systems with little component interaction on the molecular level. Where epoxy systems are concerned, the incorporation of additives into the systems results in many changes to the morphology and physical behavior of the material formed. 

Figure 8.6 illustrates the variety of morphologies which polymeric systems can adopt depending on the nature of the solvent, the polymer concentration and the nature of the polymer itself. Such diversity explains the wide range of uses in pharmacy and medicine. 

Figure 1. Morphology of the various polymerization systems described.

Several essential properties of cristobalite have influence on its applications. They include lower density than quartz (higher volume at the same mass), purity (low catalytic effect on many polymeric systems, excellent properties in exterior coatings due to low level of iron oxide), very low moisture (no need for drying in moisture sensitive systems), pure white color, less abrasive due to filler particle morphology. 

The method developed in this book is also used to provide input parameters for composite models which can be used to predict the thermoelastic and transport properties of multiphase materials. The prediction of the morphologies and properties of such materials is a very active area of research at the frontiers of materials modeling. The prediction of morphology will be discussed in Chapter 19, with emphasis on the rapidly improving advanced methods to predict thermodynamic equilibrium phase diagrams (such as self-consistent mean field theory) and to predict the dynamic pathway by which the morphology evolves (such as mesoscale simulation methods). Chapter 20 will focus on both analytical (closed-form) equations and numerical simulation methods to predict the thermoelastic properties, mechanical properties under large deformation, and transport properties of multiphase polymeric systems. 

Mesoscale simulation methods will also be discussed further in Section 19.C, in the broader contexts of multiscale modeling and of predicting the morphologies of multiphase polymeric systems. Many additional examples will be given in that discussion of their utilization in addressing technologically important problems. 

All mechanical properties depend on crystallinity, orientation and crosslinking. These three factors will all be discussed in this chapter. See also Kinloch and Young [2] and van Krevclcn [71 for discussions on the effects of crystallinity and orientation on the mechanical properties. The discussion of the morphologies and the mechanical properties of multiphase polymeric systems (such as composites and blends) will be postponed to Chapter 19 and Chapter 20, respectively, where crystallinity and orientation will be discussed further in this broad context. 

The properties of block copolymers, on the other hand, cannot be calculated without additional information concerning the block sizes, and whether or not the different blocks aggregate into domains. The results of calculations using the methods developed in this book can be inserted as input parameters into models for the thermoelastic and transport properties of multiphase polymeric systems such as blends and block copolymers of immiscible polymers, semicrystalline polymers, and polymers containing various types of fillers. A review of the morphologies and properties of multiphase materials, and of some composite models which we have found to be useful in such applications, will be postponed to Chapter 19 and Chapter 20, where the most likely future directions for research on such materials will also be pointed out. 

Most of the methods developed in this book are, by themselves, only applicable to amorphous polymers and amorphous polymeric phases. (An exception with obvious relevance to the properties of multiphase materials is the development of a physically robust predictive model for the shear viscosities of dispersions in Section 13.H.) Their combination with other types of methods to predict the properties of multiphase materials from component properties and multiphase system morphology enables us to expand their applications to include the prediction of selected properties of multiphase polymeric systems where one or more of the phases are amorphous polymers. In other words, the methods developed in this book are used to predict the properties of the amorphous polymeric phases of the multiphase system. These properties are then inserted into equations of composite models and into numerical simulation schemes (along with material parameters of the other types of components, obtained from other sources such as literature tabulations) to predict the properties of the multiphase system. We use existing composite models whenever they are adequate, and develop our own otherwise. 

The structural properties of a synthetic polymer can often be modified by the service conditions to which it becomes exposed, an example being interaction with atmospheric moisture. Water induced plasticization is a common occurrence, yet depending upon the chemistry and morphology of the polymer encountered, the nature of the interaction process may take widely different routes. Some degree of specificity must be assumed in discussions relating the state of sorbed water in different polymeric systems. 

We worked with the precept that morphologically ordered polymeric systems, of given side chain chemistry, can sequester ions, which can subsequently serve as an ionic array/tern plate for ordered protein adsorption, for example, epitaxial crystallization. Additionally, we addressed the effect of side chain motion of the substrate on the epitactic process based, in part, on... 

Another method of morphology control in multicomponent polymeric systems is by the use of mixed solvents having different affinity to the polymeric components. When the non-solvent is less volatile than the good solvent, evaporation results in a two-phase stracture. 

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