Study of the Foaming Kinetics in Epoxidized Natural Rubber Foams Crosslinked by Electron Beam Irradiation

This work focuses on studying natural rubber (NR) and epoxidized natural rubber (ENR) foams crosslinked at different absorbed doses and foamed using a chemical blowing agent. The aim is to study if the existence of epoxide groups within the natural rubber molecular structure influences the expansion capacity and the cellular structure morphology of these types of foam. This is accomplished by studying the foaming kinetics, that is, by quantifying the evolution of density and cellular structure parameters, such as cell size and cell density, as a function of foaming time. The results show that ENR foams exhibit higher cell nucleation rates and less intense cell degeneration than NR ones, which is because the presence of epoxide groups allows the polymer to reach higher crosslinking levels. Consequently, ENR foams present more homogeneous cellular structures and lower cell sizes.