Influence of chemical composition on the rheological behaviour of condensation reaction resins

A study of Melamine Formaldehyde (MF) resins of different molar ratios was undertaken to asses their chemorheological and thermorheological properties. MF resins polymerise via a polycondensation reaction involving condesation of up to 10 wt. % of water on cure. This results in rapid and extensive foaming of the resin when cured under atmospheric pressure. To accomplish the study, both foaming dynamics and bulk properties of MF were analysed; the former yielded results on the influence of initial moisture content on reaction rate and on curing kinetics including gel and vitrification times, while the latter yielded true G' and G " values and consistent glass transition temperature readings. The different molar ratios were found to affect curing kinetics in terms of large differences in gelation and vitrification times, and to yield high glass transition temperatures.