Multiple component polymer systems

Polymeric materials consisting of more than one component are produced in even larger quantities and their practical importance increases. These materials are usually stronger and/or tougher than one-component systems. In the field of metallurgy this fact has been known for centuries already metal alloys are often as old as metals themselves. For polymers the same empirical fact proved to be true. 

One can distinguish between real more-component polymeric systems (Class A), which do not contain anything else than polymeric materials, and polymer-based systems (Class B) in which isotropic polymeric materials are present together with either non-polymeric components or with already preformed oriented polymeric components (fibres or filaments) 

One can also make a distinction based on the nature of the blend of the components. This may be (1) homogeneous on a molecular or a microscopic scale or (2) heterogeneous on a macroscopic and/or microscopic scale. 

SCHEME 2.2 Classification of multiple component polymer systems (based on a less elaborate scheme of Platzer, 1971) 

Classes Subclasses (molecular/micro-scale) (micro/macro-scale) 

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Multi angle laser light scattering (SEC/MALLS), 16 Multiple-component polymer systems, 36,38 Multiplet structure, 368... 

Pure polymers are not generally the optimum materials for the best performance of final products. Therefore, polymeric materials consisting of more than one component are of practical importance. Polymers can be mixed with other polymers or different other materials. Table 4.2.6 gives an overview on a classification of multiple component polymer systems. As can be seen, a distinction can be made between two classes multiple component materials consisting of different types of polymers or monomers (A), and materials with an isotropic polymer and a non-polymeric component or with already preformed oriented polymeric components, e.g. fibres, filaments (B). 

In a multiple biopolymer system, each biopolymer contributes both to the film properties and to the biopolymer-biopolymer interactions thus affecting the overall multi-component polymer system properties. Usually, these interactions have great... 

Optical KLenents. Problems which are common to many solar-related optical elements Include dirt retention, cleaning, surface abrasion, and photodegradation. A common feature of some of these problems Is that the deleterious effects occur at an Interface. Ultraviolet radiation, atmospheric components, mechanical stress, etc., can have a profound effect on performance by changing surface characteristics. The lifetimes of UV stabilizers can be limited by exudation permeability can cause harmful reactions at Interfaces and mechanical properties can be Influenced by surface crazing. In other applications mechanical behavior of the bulk polymer Is critical and virtually all applications require that the polymer system withstand multiple environmental stresses simultaneously. 

Ravati and Favis [12] generated a low percolation threshold conductive device prepared through the control of multiple encapsulation and multiple percolation effects in a five-component polymer blend system. 

A major application of solid state NMR is the study of polymer morphology. Information potentially available includes the amount and orientation of crystalline phases in semi-crystalline polymers and the domain sizes in phase-separated polymeric systems. For the determination of crystallinity, a common method is to measure Ti relaxation in NMR (or NMR for deuterated polymers). The relaxation data can often be resolved into two (or more) components, which may correspond to magnetization arising from crystalline and amorphous phases (11-15,130-134). The development of the maximum entropy regularization method has permitted more facile and less subjective analysis of the data (143). In optimal cases, multiple components can be identified. 

In the last two chapters of the book on Thermal Analysis of Polymeric Materials the link between microscopic and macroscopic descriptions of macromolecules will be discussed with a number of examples based on the thermal analysis techniques which are described in the prior chapters. Chapter 6 deals with single-component systems, Chap. 7 with multiple-component systems. It is shown in Sect. 6.2, as suggested throughout the book, that practically aU partially crystalline polymers represent nonequilibrium systems, and that thermodynamics can establish the equilibrium limits for the description. It was found, however, more recently, that equilibrium thermodynamics may be applied to local areas, often small enough to be called nanophases [1]. These local subsystems are arrested and cannot establish global equilibrium. 

Qipeng demonstrated that PCL/PVME blends were also characterised by single, composition-dependent TgS (Sect. 18.2). Similarly, all ternary blends of the three polymers exhibited single glass transition temperatures which agreed with values calculated from l/T=I(w/Tgj), an extension of Eq. (23) to multiple components. The author concluded that the polymers were miscible in all proportions but made no reference to the occurrence of PCL crystallisation in the samples. Cloud points were also determined in PCL/PVME and phenoxy/PVME blends PCL/phenoxy blends remained clear to 200 °C. All ternary systems exhibited cloud points and the minimum of the connecting surface was 108 °C at a PCL/phenoxy/PVME composition of 25/25/50. 

In this section, examples of self-assembled systems formed by simple mixing of multiple components are discussed. These components can be mixed either in the monomeric state or after supramolecular homopolymers have been formed. This type of preparation relies heavily on the thermodynamic interactions between the different components as well as on the dynamic nature of the supramolecular polymer. For each type of organization, these two features are discussed followed by representative examples from the literature. 

As discussed above, polymer blends are often heterogeneous systems consisting of multiple phases. The system is in a thermodynamic equilibrium if the chemical potentials of the components are equal in all phases. The chemical potential is defined as a change in the Gibbs energy of the system induced by the addition of one molecule of component i, while the pressure, temperature and number of other molecules are kept constant (Eq. (3.15)) ... 

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