Catalysis of the cure reaction of bisphenol A dicyanate. A DSC study

The kinetics of the thermal cure reaction of Bisphenol A dicyanate (BACY) i n presence of various transition metal acetyl acetonates and dibutyl tin di laurate (DBTDL) was investigated using dynamic differential scanning calori metry (DSC). The cure reaction involved a pregel stage corresponding to aro und 60% conversion and a postgel stage beyond that. Influence of nature and concentration of catalysts on the cure characteristics was examined and co mpared with the uncatalyzed thermal cure reaction. The activation energy (E ), preexponential factor (A), and order of reaction (n) were computed by th e Coats-Redfern method. A kinetic compensation correction was applied to th e data in both stages to normalize the E values. The normalized activation energy showed a systematic decrease with increase in catalyst concentration . The exponential relationship between E and catalyst concentration substan tiated the high propensity of the system for catalysis. At fixed concentrat ion of the catalyst, the catalytic efficiency as measured by the decrease i n E value showed dependency on the nature of the coordinated metal and stab ility of the acetyl acetonate complex. Among the acetyl acetonates, for a g iven oxidation state of the metal ions, E decreased with decrease in the st ability of the complex. A linear relationship was found to exist between ac tivation energy and the gel temperature for all the systems. Manganese and iron acetyl acetonates were identified as the most efficient catalysts. In comparison to DBTDL, ferric acetyl acetonate proved to be a more efficient catalyst. The activation parameters computed using the Coats-Redfern method agreed well with the results from two other well known integral equations. (C) 1999 John Wiley & Sons, Inc.