Measurement of Glass Transition Temperature and other Transitions

1 Measurement of Glass Transition Temperature and other Transitions 

DMTA is sensitive enough to detect even weak secondary transitions such as alpha and beta transitions in the resin matrix of a highly filled composite. In fact, all properties measured by this technique generate strong, well-defined signals that are not clonded by background noise or other interferences. 

Ruvola-Filho and Teixeira [6] observed a shifting of the a-transition in amorphous glass polyether imide films at higher temperatures around the glass transition temperature by using DMTA. These are due to the antiplasticiser effects of dichloromethane solvent on the elastic modulus of the polyether imide matrix. 

Schmaljohann and co-workers [7] showed that in aromatic hyperbranched polyesters with an increasing length of the alkyl chain, the Tg increases due to intermolecular hydrogen bonding and a low temperature thermal transition and base separation occur. 

Sircar and co-workers [8] compared experimental and data from the literature for the Tg of some common elastomers determined by different thermal analysis techniques, including DSC, TMTA, DMTA, dielectric analysis and thermally stimulated current methods. Elastomers examined include natural rubber, styrene-butadiene rubber, polyisoprene, polybutadiene, polychloroprene, nitrile rubber, ethylene-propylene diene terpolymer and butyl rubber. Tg values obtained by DSC, TMA and DMTA were compared. Experimental variables and sample details, which should be included along with Tg data were described, and the use of Tg as an indication of low temperature properties was discussed. 

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