Rubber giant crosslink

The action of a domain in a polymer melt (at constant shear stress) can be shown to be equivalent to the action of a giant crosslink in a rubber. Removing of one crosslink is accompanied by a negative free-energy change (aG2). 

Due to their high molecular masses, macromolecular substances (polymers) show particular properties not observed for any other class of materials. In many cases, the chemical nature, the size, and the structure of these giant molecules result in excellent mechanical and technical properties. They can display very long linear chains, but also cyclic, branched, crosslinked, hyperbranched, and dendritic architectures as well. The thermoplastic behaviour or the possibility of crosslinking of polymeric molecules allow for convenient processing into manifold commodity products as plastics, synthetic rubber, films, fibres, and paints (Fig. 1.1). 

Crosslinked or three-dimensional network polymers - Crosslinked polymers may be represented as a three-dimensional network structure. They are crosslinked, that is they consist of insoluble and infusible three-dimensional giant molecules. Examples are thermosetting polymers such as crosslinked rubbers, resins, and so on. 

Curatives include all those chemicals and additives that are added to a rubber compound during mixing to enable the compound to cure (vulcanize) when elevated temperatures are applied. Chemically, curing (vulcanization) Involves the generation of crosslinks between the giant elastomer molecules. Without curatives present, a rubber compound normally cannot cure. The useful cured properties of virtually any rubber are obtained only after vulcanization has taken place. 

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