To compare the difference of morphological evolution of HDPE micropart and macropart, micropart with 200 mu m thickness and macropart with 2000 mu m thickness were prepared. The PLM images of micropart and macropart exhibited a similar skincore structure, but the micropart showed a much larger fraction of orientation layer. The SEM observation of core layer of micropart featured an unoriented lamellae structure and shear layer of micropart showed a highly oriented shish-kebab structure. The 2D-WAXD patterns of shear layer of macropart indicated twisted oriented shish-kebab (KM-I) structures, however that of micropart indicated untwisted oriented shish-kebab (KM-II) structures which was firstly found in microinjection molding. The diffraction pattern of the micropart exhibited stronger azimuthal dependence than the shear layer of macropart, indicating the most pronounced orientation of HDPE chains within lamellae. (C) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012