DMA Testing : Our Areas of Expertise
John G has been using this DMA/DMTA technique since 1981, and helped develop the Polymer Labs DMTA and then the Triton DMA (which is now the Perkin Elmer 8000 system). Also the powder material pockets which mean that a small irregular sliver of paint, or 2 to 20 milli-grammes of powder can be run in this very sensitive DMA. (This I still find quite remarkable since 2 milligrammes of powder in 700 milligrammes of stainless steel (which is 100 times stiffer than plastic) can still show up a change in modulus through the glassy state and of course change dramatically at the glass transition, Tg. So the sample sizes are from a few milligrammes of powder, through very thin fibres of 10 micron or greater diameter - such as a human hair, up to a bar of 5 or 6mm x 10mm x 50mm - which can be as stiff as a CF composite or even a metal with a very thin coating on it.
DMA comes in two forms - the very large apparatus for measuring rubbers in shear of compression at up to 5 Mega Newtons for earthquake foundations etc. where the samples are large so equilibration at each set Temperature T is necessary before a strain or frequency sweep is performed. Then there is the much smaller systems which we use where the sample size allows for thermal scanning at up to 5°C per minute. So we can vibrate at say 3 different frequencies (multiplexing) whilst scanning at say 2°C/min and obtain very good data showing the difference between Tm and Tg for example on unknown co-polymers or even where there is just a few % resin in a composite material which some DMAs and the DSC cannot see at all.
Sensitivity of coatings on metal of 0.5 to 1mm thickness is microns of thickness to see Tg. As well as my old, but well looked-after Triton DMA we can use the TA Instruments DMA too.