Two processes of α-phase formation in polypropylene at high supercooling

• An additional crystallization process of polypropylene is obtained the first time.
• This process occurs in the temperature range between 45 °C and 75 °C.
• In this temperature range α-phase crystals are formed.
• We interpret this process as differently nucleated α-phase crystallization.

The non-isothermal and isothermal crystallization of different types of commercial polypropylenes (PP) are investigated by fast scanning calorimetry and wide-angle X-ray scattering. Typically, PP shows two different crystallization processes: below 55 °C the mesophase formation and at higher temperatures the α-phase formation. Here we report the first observation of an additional crystallization process in some PP-types. It is observed between 45 °C and 75 °C, and is understood as a consequence of an additional nucleation of α-phase crystals.

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