Polymer processes, classification

Fig. 19.11 shows that the treatment of the solidification of polymers is the most demanding undertaking. The required theoretical basis has been developed by Schneider et al. (1988) and developed further by Eder (see the above reviews). With the aid of the latter author a mathematical expression could be found for the process classification number Jk, i.e. the Janeschitz-Kriegl number, as has been called by Astarita (1987) The said mathematical expression reads... 

Delaney KD, Bissacco G, Kennedy D (2012) Structured review and classification of demolding issues and proven solutions. Int Polym Process 27 77-90... 

Synthetic polymers are formed by the polymerization of monomers. Polymerization processes are basically of two types addition polymerization or polycondensation. The resulting polymers are classified by their mode of formation as either addition polymers or condensation polymers. This classification of polymerization processes and, hence of the resulting polymers, leads to an incongruous situation. For example, polyethylene, which is normally produced by addition polymerization of the monomer, ethylene, can also be produced from diazomethane by polycondensation, e.g.,... 

The classification given in Table 1 is based on the process, ie, thermosetting or thermoplastic, by which polymers in general are formed into usehil articles and on the mechanical properties, ie, rigid, flexible, or mbbery, of the final product. AH commercial polymers used for molding, extmsion, etc, fit into one of these six classifications the thermoplastic elastomers are the newest. 

Table 1. Classification of Polymers According to Properties and Processing...

In Section 13.2, we introduce the materials used in OLEDs. The most obvious classification of the organic materials used in OLEDs is small molecule versus polymer. This distinction relates more to the processing methods used than to the basic principles of operation of the final device. Small molecule materials are typically coated by thermal evaporation in vacuum, whereas polymers are usually spin-coated from solution. Vacuum evaporation lends itself to easy coaling of successive layers. With solution processing, one must consider the compatibility of each layer with the solvents used for coating subsequent layers. Increasingly, multilayered polymer devices arc being described in the literature and, naturally, hybrid devices with layers of both polymer and small molecule have been made. 

Classification of Processes and Reactors. Most styrene polymers are produced by batch suspension or continuous mass processes. Some are produced by batch mass processes. Mass in this sense includes bulk polymerization of the polymer... 

The chemical and physical properties of the polymers obtained by these alternate methods are identical, except insofar as they are affected by differences in molecular weight. In order to avoid the confusion which would result if classification of the products were to be based on the method of synthesis actually employed in each case, it has been proposed that the substance be referred to as a condensation polymer in such instances, irrespective of whether a condensation or an addition polymerization process was used in its preparation. The cyclic compound is after all a condensation product of one or more bifunctional compounds, and in this sense the linear polymer obtained from the cyclic intermediate can be regarded as the polymeric derivative of the bifunctional monomer(s). Furthermore, each of the polymers listed in Table III may be degraded to bifunctional monomers differing in composition from the structural unit, although such degradation of polyethylene oxide and the polythioether may be difficult. Apart from the demands of any particular definition, it is clearly desirable to include all of these substances among the condensation... 

See also Axial dispersion aerosols, 1 774-775 aqueous, 18 292 behavior of, 15 685-690 chemical processing aids, 8 705-711 chromatic, 11 134 classification, 8 698-699 colorants for plastics, 7 360-361 donor-acceptor interactions, 8 707-708 electrostatic repulsion, 8 732-734 in filled networks, 22 572 of filled polymers, 11 307-308 flow, 8 726-730 flushing, 8 711... 

The development of polymer science with the study of new polymerization processes and polymers showed that the original classification by Carothers was not entirely adequate and left much to be desired. Thus, for example, consider the polyurethanes, which are formed by the reaction of diols with diisocyanates without the elimination of any small molecule ... 

In many cases, these polymer chains take on a rod-like (calamitic LCPs) or even disc-like (discotic LCPs) conformation, but this does not affect the overall structural classification scheme. There are many organic compounds, though not polymeric in nature, that exhibit liquid crystallinity and play important roles in biological processes. For example, arteriosclerosis is possibly caused by the formation of a cholesterol containing liquid crystal in the arteries of the heart. Similarly, cell wall membranes are generally considered to have liquid crystalline properties. As interesting as these examples of liquid crystallinity in small, organic compounds are, we must limit the current discussion to polymers only. 

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