Novel technique for following the rigidity changes accompanying the curing of polymers

A method is described for measuring the rigidity of a curing polymer system throughout its complete course of reaction (liquid to solid). In this technique, a braided fiber (nylon), impregnated with the polymer system to be studied, is used as the supporting member for a free, torsionally vibrating mass. From the frequency of the vibration, the apparent rigidity modulus Ḡ of the impregnated braid is calculated. The rigidity of the reacting polymer is thus followed nondestructively during the curing period. In a further development, the term relative rigidity Ḡ/Ḡ0 is introduced to normalize the rigidity parameter to a more experimentally adaptable quantity. The curing behavior of several types of polymer is presented to illustrate the general utility of the method.