a b s t r a c tThe thermal characteristics of bottle grade recycled PET pellets contaminated with 5% PP prepared by multiple extrusions were studied by differential scanning calorimetry (DSC) at constant heating rate of 10 C/min for various extrusion cycles. The peak temperature of crystallization T c , the enthalpy of crystallization DH c and the degree of crystallinity X c were found to be dependent on the number of extrusion cycles. From the dependence on extrusion cycles, the analysis of the crystallization mechanism by Avrami model has been determined, the Avrami exponent n and the rate constant Z t were calculated and the influence of the 5% PP on the bottle grade recycled PET matrix during multiple extrusions and its effect on crystallinity was thoroughly discussed.