# Correctness of DSC curve for polyamid or polyester

I did a DSC on a part of an alternator car belt. We already found out that it should by a polyester or a polyamid. But then we got the following DSC curve:

How is it possible that the glass transition temperature is around 39°C for a polyamid or a polyester?

• Did the recording really start at $\pu{-80 ^\circ{}C}$, as the abscissa indicates? Routine DSC I saw so far (Mettler) start their scan at about $\pu{+20 ^\circ{}C}$. And then, your characterisation already stops at $\pu{100 ^\circ{}C}$, a bit early. – Buttonwood May 21 '17 at 21:22