Practical Aspects of Polymer Blending

Polymer blends have become a very important subject for scientific investigation in recent years because of their growing commercial acceptance. Copolymerizalion and blending are alternative routes for modilications of properties of polymers. Blending is the less expensive method. It does not always provide a satisfactory alternative to copolymerization, of course, but polymer blends have been successfully used in an increasing number of applications in recent years. Such successes encourage more attempts to apply this technique to a wider range of problems in polymer-related industries. 

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Practical Aspects of Polymer Blending 12.5.1 Objectives in Making Blends... 

Few years ago, to alleviate the situation, ChemTec Publishing created a new research journal Polymer Networks Blends. The journal s goal has been to serve as a vehicle for stimulating application of fundamental research in the practice of blends development and uses by the industry. More recently, the publisher decided to develop a series of reference publications conceived to build a bridge between the academic and industrial aspects of polymer blends. At present, four major publications are in preparation ... 

The phenomenon of carbon black (CB) particles gathering at the interface in binary heterogeneous polymer blends is not only of fundamental interest, but has a practical aspect as a method for improving the electric conductivity of composite polymer materials [1-12] and the mechanical properties of polymer blends with a low interfacial adhesion [13-15], The works examining the causes of this phenomenon are few in nmnber. Most of authors only note that some part of a filler tends to accmnulate at the interface. Contradictory assmnptions of the conditions necessary for such localization are made. 

The manufacture of polymer blends from insulating conventional polymers (regardless of whether these are thermoplastic or nonthermoplastic polymers) and intrinsically conductive (homo-) polymers (especially PAni) by physical methods begins after the polymerization of the individual components. This has not only practical but also fundamental theoretical aspects. 

A certain period in polymer publications has been studied, when such characterizations as technological , operational , mechanic , forced , segmental etc. were added to the term compatibility to describe properties of thermodynamically incompatible polymers or polymers with a limited compatibility. In our opinion this differentiation doesn t have a reasonable physical meaning. This problem has more than once been referred to in publications (see, for example [109,163]). Application of these amendments could he stipulated hy kinetic aspects ignored during analysis of mixing and phase separation processes in polymer hlends and failed attempts to provide scientific base under practical preparation methods of polymer blends with satisfactory ( ) properties . 

Since most other modeling techniques for polymers are extremely demanding, the limited capabilities of COSMO-RS for efficient prediction of solubilities in polymers can be of great help in practical applications when suitable polymers with certain solubility requirements are desired. One application may be the selection of appropriate membrane polymers for certain separation processes. Predictions of drug solubility in polymers are sometimes of interest for pharmaceutical applications. Furthermore, it is most likely that COSMO-RS can also be used to investigate the mutual compatibility of polymers for blends. This aspect, and many other aspects of the potential of COSMO-RS for polymer modeling, still awaits systematic investigation. 

With better understanding of the mechanism of degradation and stabilization, there undoubtedly will be an increased effort to produce polymers with greater photothermal/radiation resistance and also more effective stabilizers to achieve this end. Thus, the study of degradation and stabilization aspects of ethylene-propylene copolymers and their blends (and generally of multiphase polymer blends) appears to be both intellectually stimulating and of practical importance. 

One area of material science where ET-IR imaging has proved to be of extraordinary importance, in terms of scientific and practical aspects, is that of polymer analysis and polymer physics. In order to illustrate the broad range of appUcability in these disciplines, we will now discuss some selected examples in detail, ranging from phase separation in biopolymer blends, the use of polarized radiation to produce anisotropy images of inhomogeneously deformed polymer films, and determination of the diffusion coefficient of D2O in an aliphatic polyamide. 

In further quest for development of more efficient materials, clue had been provided by ongoing mixed (interdisciplinary) research. Intelligently the immediate inspiration was drawn from mixed systems (i.e., blends, alloys or composites) based on conventional polymers, metals, and ceramics. Soon it was realized that the already established wide applicability of CPs/ICPs can be further expended by formation of multiscale/multiphase systems, e.g., a wide variety of electronically, electrochemically, and/or optoelec-tronically active blends (BLNs), conjugated copolymers (CCPs) and composites (CMPs) [both bulk or nanocomposites (NCs)] or hybrids (HYBs) [11,14-16,52,109,113,120,128,131,132,191-205]. The next section of the chapter covers the fundamental aspects of CP-based BLNs, CCPs, and NCs/ HYBs. In particular, their definitions (including etymology), types, properties, synthetic routes, and practical applications have been discussed with the help of suitable examples from the open literature. 

The application of the dynamic SCF theory [97] or EPD [29,31,109] to the collective dynamics of concentration fluctuations and the relation between the dynamics of collective concentration fluctuations and the single chain dynamics is an additional, practically important aspect. We have merely illustrated the simplest possible case—the early stages of spontaneous phase separation within purely diffusive dynamics. In applications the hydrodynamic effects [110,111], shear and viscoelasticity [112] might become important. Even deceptively simple situations—like nucleation phenomena in binary polymer blends—still pose challenging questions [113]. Also the assumption of local equilibrium for the chain conformations, which allows us to use the SCE free energy functional, has to be questioned critically. Methods have been devised to incorporate some of these complications [76,96,99, 111, 112] but the development in this area is still in its early stages. 

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