Ultrasonic relaxation polymerization

The system in question polymerizes and therefore the kinetics can not be followed by the traditional methods. The ultrasonic technique, however has proved usefull for the kinetic investigation (9-11). The ultrasonic relaxation spectrum indicates that the kinetics can be described by a single relaxation time. This might be surprising at a first glance because eqn.(21) predicts n-1 relaxation times. The simplest way of approaching this situation is based on the point of view that the sound wave detects... 

In the condensation reaction between a trifunctional alcohol and a difunctional isocyanate, gel formation is marked by significant changes in the velocity and attenuation in the MHz region. The relaxation in the isolated monomers can be ascribed to a combination of intra- and inter-molecular processes. Intermolecular relaxation occurs in the hydrogen-bonded structure formed as a result of hydroxyl interactions. Reaction between the isocyanate and alcohol leads to the possibility of normal mode contributions to the relaxation spectrum and consequent increase in the ultrasonic attenuation. Detailed analysis of the data is difficult because of the complex topography generated by the reaction of di- and tri-functional monomers. This study does however once more illustrate the possibility of using ultrasonic techniques to monitor polymerization processes. 

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