This part of ISO 6721 specifies methods for determining a value of the glass transition temperature (Tg) from the dynamic mechanical properties measured during a linear temperature scan under heating conditions. The glass transition temperature is an indicator of the transition from a glassy state to a rubbery state. Usually referred to as dynamic mechanical analysis (DMA), the methods and their associated procedures can be applied to unreinforced and filled polymers, foams, rubbers, adhesives and fibre-reinforced plastics/composites. Different modes (e.g. flexure, compression, tension) of dynamic mechanical analysis can be applied, as appropriate, to the form of the source material. NOTE For tests undertaken in the flexure or torsion mode, an additional procedure is included to identify the severity of the influences of thermal lag on the measured data (see Annex B).