Respected All,
Mostly, thermal properties (e.g. Tg or Tm) of organic composites are not known very well. Therefore there will be, always remains uncertainties in the maximum selected temperature range upto which the DSC measure. Some time molted polymer composite may damage the instrument.
It is a general rule to carry out TGA analysis to understand the degration begavior. This will give you the safe temperature range for selection. If TGA machine is not available, you must know the Tg or Tm of the polymer used in composite. Minimum temperature you must start is at least 20 degreeC below thermal transition and minimum temperature above should be similarly 20 degree higher. You may take wider range but never smaller.
In some case at high temperature there is reagreegation of segments etc. If known allow it for that also.
Dr. Samui,
Dr. that is I want to tell you or better says ask you, that if polymer composite (which will not studied more) I use for thermal properties (especially Tg or Tm) not calibrated very well, than higher temperature range selection will be quite difficult. Than what are the parameters of selection of higher limit of temperature ?
Dear Rinkesh
You need not to use any sophisticated instrument to find out melting temperature. This can be measured easily simply by using a calibrated thermocouple. This will set highest limit of temperature up to which you can go in DSC. If you do not know glass transition temperature, no problem. you can start with the minimum temperature available in your DSC instrument. On heating, first you will get glass transition then crystallization and finally melting temperature.
I agree with Prof Samui, TGA should be done first before doing any DSC measurement to give a safety range of temperature when using DSC/DTA. TGA will give information of degradation temperature of the sample in which should be avoid when using DSC. For example: PVA degraded mainly at 270C as shown by TGA, then i will do DSC measument in the range of room temperature up to 200 C. In case of polymer composite, generally the degradation temperature of polymer will increase depending on the type, concentration, method of mixing with the filler.
I like to add that if the specific data is not available with you and you might be having instrument availability problem, consider general polymer nature. You try DSC up to 250 or if possible up to 300 degree C.
you can use burning test before the DSC or TG test and estimate the tg and tm approximatlly
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