Abstract
The dynamic shear properties of two organic glasses, 2'-hydroxy- 2:4:4:6:5'-pentamethylflavan and glycerol sextol (cyclo-hexanol) phthalate, have been studied at frequencies between 10-4 c/s and 104 c/s. A brief outline is given of similar measurements on other types of materials and the measured properties of the two glasses are contrasted with those of polymethyl methacrylate in detail. Calculations have been made of the approximate relaxation-time spectra and it is shown that the behaviour of hydroxy-pentamethylflavan is governed by a single activation process over the major part of the frequency range considered. The results suggest that a correlation exists between the mechanical and chemical properties of the glasses.