The meaning and aim of thermo-mechanical analysis are explained. The basic principle of the construction of the thermo-mechanical analyser developed in our laboratory is described briefly. With this instrument

we can

during a programmed temperature rise

measure the length changes of the fibre under a fixed tension

the stress changes in the fibre under fixed length or the stress-strain relationship when both quantities vary. Finally

the transition temperatures of acrylic fibres are estimated from characteristic curves

obtained by thermo-mechanical analysis

followed by a short discussion of the nature of these transitions.