The mechanical properties of films. II. The glass/rubber transition temperature

A mechanical method of investigating transitional behaviour is described in which the stress developed in supported polymer films is observed as a function of temperature. The method has given information on transition temperatures which has been useful in work involving the dynamic elastic properties of the polymers and the WLF equation. The method is not sufficiently sensitive to resolve all the transitions observed dilatometrically and an empirical method of ‘averaging’ the latter gave results consistently 10–15°c higher than the ‘mechanical’ value.