Thinking about Rheology and DMA

As we mentioned, we recently attended the U. Mass Amherst Rheology Course, run by Dr. Winters and Dr. Wagner. It ran from the very practical to the esoteric and was easily worth the cost (400 USD) for four half days online. About 35 people ranging from academics to engineers to analytical chemists attended. Even one poor soul from marketing.

One thing that struck me again was how successful certain unnamed instrument companies have been at separating the DMA instruments from rheology, which is where it developed. The method - applying an oscillatory force/distortion to a sample - is the same. Same approach to the analysis, same kinds of data. Just axial force instead of torsional. DMA samples tend to be solids, while rheometer samples tend to me melts, liquids, suspensions, or emulsions. Note the “tend.” Both instruments will run both sets of samples. Really, separating them makes as much sense as deciding grilling hot dogs is a different cooking method as grilling burgers.

I do admit that the data analysis for DMA may seem simpler. After all, Henning’s class starts with generating mastercurves, which DMA uses generally call TTS (time temperature superposition). For DMA this is an advanced technique. BUT, and this is a big but, most rheometer users don’t either. They measure shear or shear rate or frequency behavior. They look at temperature dependence.

So, over the next months, we are going to be looking at rheologic applications to various materials. As we do, keep in mind that the instrumental distinction is, to a very large degree, artificial.