Journal of Applied Polymer Science, Vol.55, No.1, 39-45, 1995
Cross-Linking of Poly(Methyl Methacrylate) by Aminolysis of Ester Functions with Diamines
The cross-linking of poly(methyl methacrylate) (PMMA) macromolecules by primary aliphatic diamines was carried out at 413-473 K, above the polymer glass transition temperature. The spherical grains of the suspension-prepared polymer (0.25-0.8 mm) and the molar ratio to amine above 20 were used. The reaction is characterized by an induction period before the macroscopic gel was observed and by fast network formation. Both phenomena are temperature-dependent (87 +/- 2 kJ mol-1). The rate of gelation is dependent also on the type of diamine; the shorter induction period of gelation and the higher rate of cross-linking were observed when amino groups were separated with longer alkyl chains. From the kinetics of amine uptake with PMMA, however, it can be concluded that gel formation is influenced also by the reactivity of amine in the transamination reaction and by the amount of bounded diamine. Aminolysis of PMMA ester groups proceeds from the very beginning of heating of the reaction charge. The polymer cross-linking prevails when there is more than 60% of diamine attached to PMMA in dependence on the amine type used.