Studies on a dicyanate containing four phenylene rings and polycyanurate blends. 2. Application of mathematical models to the catalysed polymerization process

Selected blends of bis-4-(4-cyanatophenoxy)phenyl sulphone with a commercial dicyanate, 2,2-bis(4-cyanatophenyl)propane are analysed using differential scanning calorimetry (DCS) to examine the processes of the aluminium-catalysed thermal polymerisation. Kinetic treatment of these data show that the kinetics of the formation of the bis-4-(4-cyanatophenoxy)phenyl sulphone homopolymer were fitted with just two processes, but three processes were required for the 2,2-bis(4-cyanatophenyl)propane homopolymer, for which a more complex thermogram was obtained. When considering the polymerisation kinetics of binary blends of the monomers it was necessary to select the minimum number of kinetic parameters to obtain the best fits to the data. The binary blends generally show trends in the data that reflect the monomer composition. The parameters derived from two kinetic methods are broadly in agreement; the kinetic treatment of the thermal data for 2,2-bis(4-cyanatophenyl)propane monomer suggests the presence of at least one impurity and this is supported by spectroscopic and chromatographic analyses. The latter was not observed for bis-4-(4-cyanatophenoxy)phenyl sulphone, a monomer found to be of a higher purity by chromatography. From the kinetic analysis of the thermal data (from dynamic DSC), the mathematical model predicts that, following an isothermal cure regime at 450 K, bis-4-(4-cyanatophenoxy)phenyl sulphone should reach a conversion of 90% after ca. 33 min. The empirical data for this isothermal experiment show that bis-4-(4-cyanatophenoxy)phenyl sulphone reaches a conversion of 73% after 33 min and 87% after 2 h at 450 K.