New way of using rheometers in scanning mode for the cure of rubbers

Abstract

Rheometers, especially the moving die rheometer (MDR), is used under isothermal conditions for the cure of rubbers. Thus, at least three experiments are necessary at different temperatures selected within a rather narrow temperature window, for determining the kinetic parameters of the cure. Moreover, it takes some time for the sample to attain the selected temperature, and for a high temperature of the dies, the reaction takes place before thermal equilibrium has reached. With this new way of using the rheometer, the dies with the rubber samples in them are heated from the room temperature up to the selected final temperature, with a constant heating rate. Calculations have been done for evaluating the performances of this method. The kinetic parameters such as the activation energy and the pre-exponential factor, as well as the order of the overall reaction, are obtained from only one experiment. The temperature in the sample is constant and nearly the same as that of the heating dies. The profiles of temperature and of the state of cure developed through the sample thickness are rather flat during all the processes. The parameter of interest, with the value of the heating rate, should be between 2 and 10°C/min, and perhaps much better between 2 and 5°C/min.