Polymer Networks Based on the Diepoxide-Diisocyanate Reaction Catalyzed by Tertiary Amines

MARÍA J. GALANTE; R.J.J. WILLIAMS

JOURNAL OF APPLIED POLYMER SCIENCE

JOHN WILEY & SONS INC

Lugar: New York; Año: 1995 vol. 55 p. 89 - 98

0021-8995

Reactions taking place in a system consisting of a diepoxide (DGEBA, diglycidylether ofbisphenol A) and a diisocyanate (TDI 80 : 20, toluene diisocyanate), catalyzed by a tertiaryamine (BDMA, benzyldimethylamine), were followed by differential scanning calorimetry(DSC), infrared spectroscopy (FTIR), and chemical titration of isocyanate groups in thepre-gel stage. It was found that the main reactions took place in series, in steps of increasingtemperature: (i) isocyanurate formation, (ii) epoxy-isocyanate reaction leading to oxazolidonerings, and (iii) isocyanurate decomposition by epoxy groups producing oxazolidonerings. Isocyanurate rings were stable in the presence of epoxides and an isocyanate excess[reaction (ii) was faster than (iii)]. Epoxy homopolymerization (secondary reaction) occurredin parallel with steps (ii) and (iii). Step (i) took place by two different mechanisms and ledto a maximum conversion, possibly limited by topological restrictions. A kinetic study ofTDI trimerization in the presence of an equimolar amount of DGEBA and variable amountsof BDMA led to a third-order regression with an activation energy E = 43 kJ/mol.