The Influence of Monomer Chemical Structure on Late - Stage Cure Kinetics of 5

In the production of structures made from reinforced cyanate ester resins, nearly complete cyclotrimerization of the resin with concomitant macromolecular network formation must be achieved in order to ensure adequate mechanical performance and durability of the structures. In the course of developing a wide variety of new cyanate ester resins, as well as in studies of cocured blends, it has become apparent that some resins can be fully cured into robust networks quite readily under benign conditions, even with a very limited degree of catalysis. Others, though, require post-cure at such high temperatures that the resin undergoes thermochemical degradation during the cure process, while still others are unable to achieve a high degree of cure or form a macromolecular network under any known conditions. Because of the highly selective nature of cyanate ester cyclotrimerization, these differences provide an exceptional opportunity to study the influence of the molecular structure of the monomer on the ability to form a fully cured network structure. For dicyanates of the bisphenol type in particular, studies of cure kinetics and network formation employing differential scanning calorimetry, infrared spectroscopy, and thermomechanical analysis have helped to illuminate important aspects of the links among molecular rigidity, molecular topology, thermal activation, and network formation.