The influence of annealing temperature on the kinetics of polymorphic changes and mechanical properties within the time in isotactic poly(1-butene) (PB-1) has been investigated by wide-angle X-ray scattering and tensile testing. Extruded tapes of PB-1 have been exposed to several annealing temperatures: -22, +5, +22, +40 and +60 degrees C. The evolution of content of Phase I for various annealing temperatures upon time shows predominantly S-shaped trend. Annealing temperature considerably affects the overall rate of transformation in PB-1. On the other hand, the resulting mechanical properties are solely controlled by the polymorphic composition. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012