Isothermal ultra-cooling crystallization tests were conducted on three blown film grade bimodal HDPE resins using an ultrafast scanning calorimeter, the Flash DSC. Isothermal tests were performed to study the regime transition, the thermal nucleation and the spherulitical growth using the Hoffman-Lauritzen theory in a range between 90 degrees C and 116 degrees C. Temperature profile estimations using such data were in good agreement with actual blown film process data. (C) 2016 Wiley Periodicals, Inc.