The figure shows DSC cooling (blue) and 2nd heating (green) curves (step: 10 K/min) for a commercial sample supplied as Atactic Polypropylene (APP). The heating curve illustrates two major endotherms at 119.6 and 152.4 oC. However, in the cooling curve, there is only one crystallization peak located at Tc=105.8. How can the two melting peaks be merged in one crystallization peak in the cooling thermogram?

Another point is the two Tm values that as I searched the one at ca 150 corresponds to IPP but I could not identify a source for the one at 119.6. Can this also be related to PP?

I would be much grateful if you could help me with your expertise to get answers to these questions.