Thermoplastic elastomers thermosetting polymers

Elastomer Thermoplastic or thermoset polymer that can stretch by a large extent and then return to its original shape without permanent deformatimi. Elastomers are only slightly... 

The majority of lining materials are organic in nature and composed of thermoplastic, or thermoset, polymers and elastomers. Inorganic lining materials include glass, brick, and mortars. 

Abstract Polymers are macromolecules derived by the combination of one or more chemical units (monomers) that repeat themselves along the molecule. The lUPAC Gold Book defines a polymer as A molecule of high relative molecular mass, the structure of which essentially comprises the multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass. Several ways of classification can be adopted depending on their source (natural and synthetic), their structure (linear, branched and crosslinked), the polymerization mechanism (step-growth and chain polymers) and molecular forces (Elastomers, fibres, thermoplastic and thermosetting polymers). In this chapter, the molecular mechanisms and kinetic of polymer formation reactions were explored and particular attention was devoted to the main polymerization techniques. Finally, an overview of the most employed synthetic materials in biomedical field is performed. 

As with all thermoplastic elastomers, the copolyesterethers can be processed as thermoplastics. They are linear polymers and contain no chemical cross-links, thus the vulcanisation step needed for thermosetting elastomers is eliminated and scrap elastomer can be re-used in the same process as virgin material (176—180). 

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. 

This chapter discusses synthetic polymers based primarily on monomers produced from petroleum chemicals. The first section covers the synthesis of thermoplastics and engineering resins. The second part reviews thermosetting plastics and their uses. The third part discusses the chemistry of synthetic rubbers, including a brief review on thermoplastic elastomers, which are generally not used for tire production but to make other rubber products. The last section addresses synthetic fibers. 

Resultant multiphase copolymers displayed properties ranging from soluble thermoplastic elastomers and engineering polymers to intractable thermosets, depending on the backbone composition and orientation, and especially the level of ODA incorpora-... 

Thermoplastics are more suitable for recycling than elastomers or thermosetting polymers. Thermoplastics can be heated above their melting temperatures and then recast into new shapes. Elastomers and thermosets, on the other hand, have extensive cross-linking networks that must be destroyed and then reformed in the process of recycling. Processes that destroy cross-linking, however, generally break down the polymer beyond the point at which it can be easily reconstituted. 

When a thermoplastic polyurethane elastomer is heated above the melting point of its hard blocks, the chains can flow and the polymer can be molded to a new shape. When the polymer cools, new hard blocks form, recreating the physical crosslinks. We take advantage of these properties to mold elastomeric items that do not need to be cured like conventional rubbers. Scrap moldings, sprues, etc. can be recycled directly back to the extruder, which increases the efficiency of this process. In contrast, chemically crosslinked elastomers, which are thermosetting polymers, cannot be reprocessed after they have been cured. 

Both thermoplastics and thermosets can be used in four of the five major application areas plastics, elastomers, coatings, and adhesives. But, only thermoplastics can be used in making fibers. During the spinning and drawing process of fiber processing, it s necessary to orient the molecules. Only unbranched, linear polymers (not thermosets) are capable of orientation. 

The crosslinking reaction is an extremely important one from the commercial standpoint. Crosslinked plastics are increasingly used as engineering materials because of their excellent stability toward elevated temperatures and physical stress. They are dimensionally stable under a wide variety of conditions due to their rigid network structure. Such polymers will not flow when heated and are termed thermosetting polymers or simply thermosets. More than 10 billion pounds of thermosets are produced annually in the United States. Plastics that soften and flow when heated, that is, uncrosslinked plastics, are called thermoplastics. Most of the polymers produced by chain polymerization are thermoplastics. Elastomers are a category of polymers produced by chain polymerization that are crosslinked (Sec. 1-3), but the crosslinking reactions are different from those described here (Sec. 9-2). 

Although the technological basis of all fluorine-containing plastics and most elastomers continues to be the free radical polymerization of fluoroolefins, which themselves are based on the vastly greater fluorocarbon refrigerant industry, important advances have been made in the past two decades These include primarily the production of polymers that are more resistant to degradation by heat, oxidation, bases, and solvents, as well as polymers that are more easily processable, that is, able to be converted mto their final forms for use, whether by thermoplastic or thermoset processes [1,2,3,4]... 

Polyurethanes are a group of organic polymers that are normally grouped with rubbers. Rubbers are often referred to as elastomers. Elastomers means stretchy materials. Elastomers/rubbers may be either thermoplastic or thermoset, depending on the chemistry and processing of the materials. 

It is possible to classify polymers by their structure as linear, branched, cross-linked, and network polymers. In some polymers, called homopolymers, merely one monomer (a) is used for the formation of the chains, while in others two or more diverse monomers (a,p,y,...) can be combined to get different structures forming copolymers of linear, branched, cross-linked, and network polymeric molecular structures. Besides, on the basis of their properties, polymers are categorized as thermoplastics, elastomers, and thermosets. Thermoplastics are the majority of the polymers in use. They are linear or branched polymers characterized by the fact that they soften or melt, reversibly, when heated. Elastomers are cross-linked polymers that are highly elastic, that is, they can be lengthened or compressed to a considerable extent reversibly. Finally, thermosets are network polymers that are normally rigid and when heated do not soften or melt reversibly. 

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