Time-temperature-transformation analysis of an alkyd-amino resin system

Abstract

The curing behaviour of a thermosetting acrylic-amino-formaldehyde resin matrix has been investigated by rheological, thermogravimetric, and thermomechanical analysis. The time-temperature-transformation (TTT) diagram of the solventless resin matrix has been constructed. The gelation curve could be fitted with a power-function of Tgel=118.14·tgel-01238. With the help of this function the conditions for gelation can be calculated, and storability of the matrix can be predicted. The onset temperature of thermooxydative decomposition is 220°C, and the maximum loss of mass belonging to this temperature was found to be 16.3%, corresponding to the ultimate conversion of curing. From iso-Tcure diagrams determined by isothermal thermogravimetric analysis, the iso-curing time (iso-tcure) and iso-mass loss curves of the TTT diagram have been constructed. The iso-Tcure diagrams determined by TMA measurements, served the construction of the iso-Tcure and iso-glass transition temperature (iso-Tg) diagrams. The Tg of the fully cured system (Tg∞) was found to be 30°C. The iso-Tg line of 30°C represents the ultimate conversion of the cured system, up to which no degradation takes place. This curve runs below the ultimate conversion determined by thermogravimetric measurements, meaning that above 160°C decomposition takes place simultaneously with curing reactions as supported by the increasing tangent of the straight lines fitted to the last section of thermogravimetric iso-Tcure diagrams. The Tg of the matrix before the cure (Tg0) is less than 0°C. This means that the system is in its rubbery physical state during the curing process.