A facile method for the study of slow physical and chemical processes in polymeric systems

A method is described for continuously following a long-duration process in a complex polymeric system by isothermal calorimetry. Computerized models for slow physical or chemical processes have been applied to calorimetric runs under different conditions and these have given information in the form of thermodynamic and kinetic data. The method also gives a means of determining the relationship between molecular weight and functionality for one of the polymers used, the order of reaction, and the degree of conversion before the start of the measurements. An example is given of a kinetic study of the reaction of hydroxyl-terminated polybutadiene with two different diisocyanates. The temperature dependence of the formation of urethanes, the rate constants, and the degree of conversion before the start of the measurements were determined as well as the heat of reaction for the formation of urethanes using hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI) as curing agents. The results have been compared with other kinetic studies of these systems.