ABSTRACT
Generally two types of network may be developed. A classical network obtained from an polymer with cross-linkable reactive sites along the chains and a model network made up of polymer chains with sticky end groups. Polymer systems can be converted to network structure by random crosslinking. Then, classical networks are obtained via radiation (13) or via chemical exchange reaction (14,15). However, the classical network formation results in elastomers with ill defined network structure and such network are limited to a functionality of three or four and average molecular weight Me between chemical cross-links is not precisely determinable from chemical measurements. Then, an example of chemical formation of a classical network is given below: The exchange reaction of ester groups in the presence of dibutyltin oxide as catalyst have been used in the molten state to cause the crosslinking of ethylene vinyl acetate (EVA) and ethylene acrylic (EMA) ester copolymer chains. The kinetics of this crosslinking reaction can been assessed by gas chromatography through titration of the evolved methyl acetate reaction which is a volatile product of the crosslinking reaction.
