Network Formation and Characterization

The chapter focuses on the network formation and characterization of polymers. The network formation during the curing reaction can be described by two major transitions: the gelation that involves the transformation of a liquid into a gel-like state and, in the case of duromers, the vitrification, the transition of the rubber state into a solid glassy state. According to their functions and structures, polymers can be classified into different categories, for instance, natural (proteins, polysaccharides, and rubber) and synthetic polymers (thermoplastics, elastomers, and duromers). The main group of synthetic polymers belongs to the class of thermoplastics and fibers, which are linear, uncross-linked polymers that can be processed into different shapes by thermal treatment. Besides other classifications, one classification of the synthetic polymer types can be done by the increasing degree of cross-linking, whereof the elastomers are slightly or moderately crosslinked, occurring very often as rubber-like flexible materials, and duromers that are highly crosslinked, available, for instance, as hard coating materials on kitchen worktops, cars, or industrially produced parquet floorings.