The Gel Point and Network Formation in the Polymerisation of an Epoxy-Amine System Including Ring Formation

Abstract

The molecular scheme, accounting for intramolecular reaction, was constructed to predict the gel point in the RA₄+R’B₂ type polymerisation. The scheme is intended to be applied for the cure of a polyoxypropylene (POP) diamine and the diglycidyl ether of bisphenol A, and based on the classification of the reaction state of the POP diamine unit. The linear sequence of structural units for the chain growth in the cure was given to define the gelation following Ahmed-Rolfes-Stepto theory, where a ring-forming parameter (λ_a) and internal concentration (P _ab) of the reactive groups can be applied to characterise the competition between intermolecular and intramolecular reaction. The chain growth was expressed by the fractional concentration of the reacted hydrogen atoms that belong to reactive amino groups, which corresponds to the extent of reaction determined experimentally. From the result of the calculation, the delay of gel point from Flory – Stockmayer criterion is shown to increase with the increase in the internal concentration.