A Vibrating Cantilever Method for the Investigation of the Dynamic Elasticity of High Polymers

A method is described for obtaining dynamic values of Young's modulus at low frequencies (20 c/s to 100 c/s) by using the forced resonance of a vibrating cantilever. Provision has been made for keeping the apparatus at a constant temperature and a few measurements of the dynamic modulus are given for polythene at 30°C and 40°C The theory of the vibrations of a cantilever including viscous internal damping is discussed. The results continue previous work carried out at higher frequencies by a different method and indicate the continuity of the dynamic modulus-frequency relation between 20 kc/s and 20 c/s for polythene `Static' measurements have also been carried out and agree with those published earlier Even at the lowest frequency the dynamic modulus is still three times the `static' value, and it is concluded that lower frequencies should be investigated