Classification of Polymer Blends

In general, one can have three types of blends plastic/plastic, rubber/rubber, and 

A polymer blend is considered miscible if the free energy of mixing is zero or negative. If two polymers are miscible, then their blend properties, such as the glass transition temperature (7 ), will be the average of the two individual polymer component proportions. This may not be desirable for many applications because such a blend will lose its elasticity at low temperatures and the upper use temperature will be lower than that of the plastic used. 

In reality, the best blend compositions are usually derived from the components that are partially miscible with each other. In general these blends are referred to as technologically compatible blends. These are the blends that provide useful compositions without the use of a compatibilizer. In blends, prepared from such technologically compatible pairs, the individual component properties such as the TgS are retained. As a result, one gets the best of both the components, that is, the blend has the lower Tg of the rubber component and the upper use temperature of the plastic segment [2]. 

Plastic/rubber blends can be divided into four groups  

2) blends of plastic and, partially or highly crosslinked rubber(s), and 

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During the course of writing this monograph, it occurred to the authors that a systematic classification of polymer blends and composites was sorely needed. In how many significantly different ways can polymers be mixed with other polymers, or with nonpolymers What interrelationships exist among the known modes, and how may we go about uncovering yet undiscovered combinations While the classification theme pervades the text, weaving in and out, the actual classifications are left to Chapter 13. 

Polymer blends are a mixture of at least two polymers, their combination being supposed to lead to new materials with different properties. The classification of polymer blends into (1) immiscible polymer blends, (2) compatible polymer blends, and (3) miscible polymer blends is given by the thermodynamic properties of the resulting compound by means of the number of glass transition temperatures observed for the final product. To improve the compatibility between the blended polymers, some additives or fillers are used. To the same extent, rubber blends are mixtures of elastomers, which are usually combined to obtain an improved product, with properties derived from each individual component. 

While this brief chapter cannot cover all of the types of polymer blends and composites known in the literature (1-3), Rgures 13.1 (4) and 13.2 (5) categorize the more important classes of polymer blends and composites, respectively. Figure 12.30 already summarized the classification of polymer interfaces. 

This chapter focuses on the apphcation of polymers in the formulation of binder blends for MIM. A brief summary of the different classifications of binder blends is presented. The rheological, thermal and mechanical properties of a feedstock with EVA/beeswax binder is discussed to highlight the influence of binder-powder interactions on these properties. 

After a temptative structure-based classification of different kinds of polymorphism, a description of possible crystallization and interconversion conditions is presented. The influence on the polymorphic behavior of comonomeric units and of a second polymeric component in miscible blends is described for some polymer systems. It is also shown that other characterization techniques, besides diffraction techniques, can be useful in the study of polymorphism in polymers. Finally, some effects of polymorphism on the properties of polymeric materials are discussed. 

Examples of Commercial Blends. In this subsection we will review some of the commercial activity in polymer blends. We find it interesting and informative to categorize examples into specific areas that relate to both technical issues associated with these mixtures, such as miscibility or crystallinity, and the intended commercial applications, such as rubbers or fibers. Other schemes of classification could be used, and the present one is not intended to be exhaustive. Likewise, there is no intent to mention all of the commercially interesting polymer blends, but rather, the present purpose is to illustrate some of the possibilities. Information about the examples used here was obtained from product literature supplied by the companies who sell these blends and from various literature references that have attempted to review commercial developments in polymer blends (70-76). 

Nauman and He [1994] simulated two dimensional spinodal decomposition for ternary polymer mixtures. Variations in volume fraction and interaction parameters of the constituents yielded a multiplicity of different morphologies, some of which were verified in the film experiments. A phase classification was presented for the morphologies obtainable with ternary polymer blends. 

Figure 13.2. Polymer blend classification scheme. Random copolymers, block copolymers, graft copolymers, IPN s, a mechanical blends of various...

Nanocomposites consist of a nanometer-scale phase in combination with another phase. While this section focuses on polymer nanocomposites, it is worth noting that other important materials can also be classed as nanocomposites—super-alloy turbine blades, for instance, and many sandwich structures in microelectronics. Dimensionality is one of the most basic classifications of a (nano)composite (Fig. 6.1). A nanoparticle-reinforced system exemplifies a zero-dimensional nanocomposite, while macroscopic particles produce a traditional filled polymer. Nanoflbers or nanowhiskers in a matrix constitute a one-dimensional nanocomposite, while large fibers give us the usual fiber composites. The two-dimensional case is based on individual layers of nanoscopic thickness embedded in a matrix, with larger layers giving rise to conventional flake-filled composites. Finally, an interpenetrating network is an example of a three-dimensional nanocomposite, while co-continuous polymer blends serve as an example of a macroscale counterpart. 

As a result of the microphase separation occurring above the critical micelle concentration, different nanostructures can be observed. Blends of homopolymer and copolymer (A/A-B) exhibit different morphologies that have been described first by Hashimoto et al. [2,3,36], who proposed a classification in terms of solubility of the copolymer brushes by the homopolymer. On the basis of these reports, De Gennes [37] and Gallot et al. [6] further investigated the structure formation in binary polymer blends. These studies established that the final morphology depends on the molecular weight of the homopolymers in the blend. As depicted in Fig. 6.4, four different situations have been described [2,3,36] ... 

Polymer Blend and IPN Classification Scheme. Of course, all of the various compositions of matter composed of two polymers are related to each other. Figure 3 (19) illustrates how the major kinds of poljnneric materials based on two kinds of mers are related to each other. The IPNs are shown here imder the occasional grafts heading, because many of the preparations have a few grafts between the two pol5uners as a consequence of free-radical chemistry, etc. Since one network of these materials is always polymerized in the presence of the other... 

Non-linear polymers comprise branched, graft, star, cyclic, and network macromolecules. Polymer blends, interpenetrating networks, and polymer-polymer complexes are summarized as macromolecular assemblies. Their skeletal structure should be reflected in the name by using an italicized connective as a prefix to the source-based name of the polymer component or components to which the prefix applies. Table 5.10.1 lists aU classifications for non-Unear macromolecules and macromolecular assemblies with their corresponding prefixes [971UP2]. Examples for nomenclature are given in Table 5.10.2 (non-linear macromolecules) and Table 5.10.3 (macromolecular assemblies). 

Ionic conductivity is a crucial parameter in the classification of polyether/PMMA/ LiCFjSO) systems for use as polym electrolytes in electrochromic "smart windows". For liquid samples (6 and 13vol% of PMMA) conductivities were even high than for pure PEG CF3S03 system (sample PO) and exceeded 10 S/cm at 25" C (Table 1). Conductivity is observed to increase (up to 10 S/cm at around lOCf Q with increase in temperature. In the temperature range 20" C to 10(T C the temperature dependence of cmKluctivity of the blend based electrolytes is VTF and follows... 

Bisphenol-A-based polycarbonate is available in different blends which maybe adapted to specific requirements by use of additives. Different Makrolon grades from Bayer AG are designated by a four-digit code, of which the first two digits denote the molecular mass of the polymer (in 1000 g/mol) and accordingly provide information on its chain length. Thus, it may also be a rough classification of the fluidity of the material [5]. 

Despite the bibliographic explosion, few efforts have been done to attempt a classification of this material s forest. Up to eight different material families of conducting polymers have been proposed (Otero 1999, 2013) basic polymers, substituted, self-doped, copolymers, blends with organic macroions, hybrids wifli inorganic macroions, composites, and salts of the different conducting polymers. Each family is constituted by hundreds of different materials, in which only a low percentage (<10 %) have been synthesized at present... 

The first chapter gives relevant information on thermoplastics and includes brief discussions of polymerization, molecular weight, molecular-weight distribution, polymer classification, polymer blends, and filled and recycled polymers. It also outlines the practical significance of melt rheology and the links it has with processing. 

Different reactive routes were adopted to generate in situ the block copolymers. A criterion of classification of the different methods can be tentatively made by considering the different compatibilizer precursors added to polymer blends a catalyst, a polymer bearing reactive groups, or a reactive additive. In the following, it is necessary to take into account that, often in industrial formulations, more than one compatibilizer precursor might be used. 

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