I am performing a temperature sweep from -100 to 100C at a 3deg/min rate to determine Tg of elastomer samples using the DMA 850 model. The data doesn't begin collecting at -100C (attached data here doesn't start until -40C) and it doesn't collect continuously until after the glass transition temperature. This behavior is consistent with other elastomers of different formulas. Is there an error in sample loading? Does anyone have advice to get smoother data collection? I don't know if I can trust this data.
I've never used a DMA 850, more of a PerkinElmer DMA 8000 user, but they are quite similar in capability so there should be no problem with this type of test. A couple of things I can think of are, firstly, do you re-clamp the samples after cooling to the glassy state? Rubbers shrink considerably more than the metal clamps, becoming loose meaning data cannot be collected.
The other possibility is the dynamic force required to meet the programmed strain exceeds the capability of the instrument, ensuring it will operate in constant stress (force) mode rather than constant strain. Not sure how the DMA 850 copes with this situation, but if it is happening, try a softer geometry.
Hope that helps.
First of all, I recommend listening to Mike Hale's advices. Also, looking at the curves of your graphs, I can assume that you have too infrequent measurements set. I.e. you should set more number of the measurements per minute in advance
Wishing you success,
P.
- Badges
- Science topic
- Similar topics
- Filing