Crystallization of poly(vinylidene fluoride) during ultra-fast cooling

Melt-crystallization of polyvinylidene fluoride (PVDF) was investigated in non-isothermal mode at ultra-high cooling rates ranging between 30-3000 K/s as well as at constant temperatures after quenching at 6000 K/s. An increase of the cooling rate above 150 K/s leads to the formation of P phase manifested by a low temperature shoulder of crystallization exotherm in addition to the a modification. At the cooling rates above 2000 K/s there is only low temperature exothermic peak that is attributed to the crystallization of pure beta modification. Isothermal crystallization was possible to realize at 110 degrees C as the lowest, resulting in alpha form. Much higher crystallization rate in submicrogram samples, as compared to standard DSC experiments, is also reported. (C) 2007 Elsevier B.V. All rights reserved.