Morphology multiphase materials

Supramolecular 10-105 nm Packing defects, nodular/globular morphology, multiphase structure Materials science Microscopies, scattering methods, thermal analysis... 

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. 

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. 

The methods developed in this book can also provide input parameters for calculations using techniques such as mean field theory and mesoscale simulations to predict the morphologies of multiphase materials (Chapter 19), and to calculations based on composite theory to predict the thermoelastic and transport properties of such materials in terms of material properties and phase morphology (Chapter 20). Material properties calculated by the correlations presented in this book can also be used as input parameters in computationally-intensive continuum mechanical simulations (for example, by finite element analysis) for the properties of composite materials and/or of finished parts with diverse sizes, shapes and configurations. The work presented in this book therefore constitutes a "bridge" from the molecular structure and fundamental material properties to the performance of finished parts. 

It will be shown below with examples that the morphology of a multiphase material is the result of an interplay between the thermodynamic drive towards its equilibrium morphology of minimum Gibbs free energy and kinetic barriers inhibiting it from reaching that morphology. 

Having described various methods to predict the morphologies of multiphase materials by multiscale modeling, we are now ready to identify some common themes between them. 

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. 

Many books provide detailed and general treatments of composite theory. Most notable are the book of Nemat-Nasser and Hori [1] for its mathematical thoroughness, and the book of Christensen [2] for its emphasis on the engineering aspects. These books, as well as many other publications, emphasize the prediction of the properties by closed-form (analytical) expressions, as will be discussed in Section 20.B. Such methods are very quick and easy to use, and especially useful in predicting the thermoelastic properties and the transport properties of multiphase materials with morphologies that are often considerably idealized. 

Figure 20.3. Comparison of the predicted Young s moduli of binary multiphase materials with morphologies best described by the aligned lamellar fiber-reinforced matrix model (Equation 20.1), the blend percolation model (Equation 20.2), and Davies model for materials with fully interpenetrating co-continuous phases (Equation 20.3). The filler Young s modulus in Equation 20.1 was assumed to be 100 times that of the matrix, and calculations were performed at Af=10, At-=100 and Af=l()00 to compare the effects of discrete filler particles with differing levels of anisotropy. It was assumed that E(hard phase)=100, pc=0.156 and (3=1.8 in Equation 20.2. For...

Chapter 5 Structure and Properties of Materials covers the solid states (glasses and crystals), mesophases (liquid, plastic, and condis crystals), and liquids. Also treated are multiphase materials, macroconformations, morphologies, defects and the prediction of mechanical and thermal properties. 

The commercial value of some polymers depends on their morphology. Thus, high-impact polystyrene (HIPS), which has an impact strength 5-10 times that of the neat polystyrene, is a multiphase material in which polybutadiene rubbery domains are distributed within the polystyrene matrix (Figure 1.4). Each of these domains contains polystyrene... 

The multiphase nature of polymeric systems (blends or composites) leads to complex rheological behavior [6]. Since flow depends on morphology, which in turn is determined by the flow field, the measurements in different flow fields usually show different behavior the basic assumptions of the continuum mechanics are invalid for multiphase materials. Furthermore, since the deformation rate at the interface is discontinuous whereas stresses are continuous, the rheological dependencies should be analyzed as stress, not strain-rate dependent. 

The performance of a material or a structure also depends on local variations due to processing conditions, such as cooling rate, shear stress, and melt-flow paths, which result in orientation and residual stress. Multiphase materials can exhibit even greater local variations in material properties than those observed in single phase polymers. A structure produced by a given process may possess significant morphological differences from test specimens. Ultimately, it may be necessary to test the impact resistance of components. 

Finer morphology and higher adhesion of the blend lead to improved mechanical properties. The morphology of the resulting two-phase (multiphase) material, and consequently its properties, depend on a number of factors, such as copolymer architecture (type, number, and molecular parameters of segments), blend composition, blending conditions, and the like (25,38,39). Creton and co-workers... 

Rials TG, Glasser WG (1990) Multiphase materials with Ugnin 5 Effect of Ugnin stracture on hydtoxypropyl ceUulose blend morphology. Polymer 31 1333-1338... 

Rials, T. G., and Glasser, W.G. (1990) Multiphase Materials with Lignin.5. Effect of Lignin Strucutre on Hydroxypropylcellulose Blend Morphology,... 

With multiphase materials, such as adhesives based on block copolymers, a temperature scan is a sensitive although indirect gauge of morphology. The temperature scan is also a useful fingerprint for a particular adhesive which is extremely valuable for quality control. 

In addition to their commercial success, the TPEs were the result of logical considerations and scientific effort, giving birth to a new field of science and technology. These multiphase materials stimulated many theoretical and experimental studies dealing not only with their chemistry, but also with their structure and morphology. 

Many types of morphologies have been reported in the literature of multiphase polymeric materials. It is the intent of this document to define only the most commonly used terms. In addition, some morphologies have historically been described by very imprecise terms that may not have universal meanings. However, if such terms are widely used they are defined here. 

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