There is a lot of variation in crystallinity calculation of polymer using DSC data inegration. To calculate % crystallinity , one needs to calculate 1st the enthalpy of fusion by intigrating peak region. Choosing wrong integration limits gives you results which you are not sure, so is there any criteria to choose integration limits?
In my opinion there is nothing to add to Johans text. In combination with the picture i think everything is pretty clear.
regards
Matthias
Hi, there is a physical interpretation or the integration limits.
These limits should identify "equilibrium states". The lower limit is just above the Tg while the upper limit is just above the rigth end tail of the melting region. (these two points reflect the "equilibrium" liquid state of the amorphous polymer. Thus, what occurs in between is only debited to the melting process)
Even if the thermogram is quite flat above Tg the method I suggest is unmistakeble.
Thanks very much Alberto D'Amore ,Well , I have PEO(polyethylene samples and data is gradually decreasing in the beggining so the 1st limit is really have an impacton actual ingetaion when calculating enthalpy of fusion. As you said, the lower limit is just above the Tg, so how could we know that point if data is not flat enough but a gradual decrease?
Imran, the reported thermograms are not clear. At first glance your calculations are wrong. You should clearly identify the glass transition temperature, that , to my knowledge is around -25°C (250 K). Thus , in order to obtain a good baseline (connecting the integration limits) I suggest starting the heating run at least from 200 K.
I agree,
you need more data on the low temperature side.
At the moment it is just a guess where to put the lower boundary.
If you have several samples and can not do new experiments (for which cause however) you could also take always the same lower boundary and get a relative information about your samples but this procedure is not recommended.
regards
Matthias
@ Alberto D'Amore and Matthias Jaunich......Bundle of thanks for comments. Alberto , I think you hit the nail, but the system which we are using is not able to go towards too lower temperature , -10 even, So, what i did to take two fixed inegration limits for all my samples as also suggested by Matthias Jaunich. My study is concentration dependent and i have scaned nearly 10 samples.
Good luck.
However, you probably will observe a change in melting temperature peak as a function of concentration. In this case, given that the procedure is absolutely not recommended, I suggest moving the lower limit of the same amount in the same direction. This will help to minimize the errors between the different samples.
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