I am new to Differential Scanning Calorimetry and have been running some tests on a co-polymer filled with particles. I have run into some strange graph shapes that a couple of hours on Google couldn't help me decode.
This is my procedure:
And my plot:
Here are the parts that I don't understand:
I would appreciate any input or any resources on the subject. So far, I have only been able to find basic explanations of DSC graphs with the standard glass transition, crystallization peaks, and melting peaks.
Note: I have repeated this trial, and continue to get similar results.
For the first issue, It would a quite an generic explanation without knowing the materials you are using. What you would want to look at is the behavior you sample with additives with respect to samples with additives i.e study the influence of the additive on your system.The hypothesis you can presented can be proved true by couple of investigative experiments.. Also, when you plot the Heat vs time when sample is held at 220C, is it a straight line?
For the second issue you are facing: The first cycle is the release of stress due to the fabrication process. One of the ways to overcome this is thermally treat your material (inside the DSC system, say isothermal at 50 C for 10 mins or scan RT to 100 at 10C/min) and then start the experiments.
Do let me know if this has been of any help
Hello, first you have to indicate the exothermal way (up or down ?) If you can cool down below 0°C you could have a flat baseline before the first peak. I think it would help. And you can also heat/cool slower to try to separate the 2 peaks. Maybe you have a glass transition followed by melting.
Thanks for the information - it seems like the thermal stresses might be the cause. I ran a full DSC run as you suggested and found no clear transition below what I was looking at, and found a melting point at around 450C. Additionally, with this run I found some surprising asymmetry in the plot.
Upon further investigation, I found that each polymer component has a glass transition below 0oC so it is a bit surprising to me that the combined Tg would be so high. I know that fillers can increase the Tg, but can it increase it this much?
As for the "softening", when I heat the polymer outside of the DSC, I can observe that it becomes much more soft and flexible around 80C. I know this can occur for a variety of reasons that may or may not include the glass transition, but you're right I don't think they would show up on the DSC plot. Does this, coupled with my plots mean then that I can conclude that this is the glass transition or should I run additional tests?
Steven Rich , Can you please explain why there's such a huge gap between heating and cooling cycle? It seems heat flow varies from -2.5 mW to 2.5 mW.
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