Abstract: The effect of injection speed on the crystallization properties of polypropylene (PP) was studied. Plotting crystallinity vs. injection velocity a “Λ” shaped curve was obtained. The orientation and lattice distortion increased, while the crystallite dimension decreased with increasing injection speed. The order of the parameters sensitive to injection speed was crystallite dimension, crystallinity, lattice distortion, orientation, crystal form.

Key words: injection speed, crystal type, orientation, lattice distortion, crystallite dimension.