Review articleEffect of multiple extrusions and influence of PP contamination on the thermal characteristics of bottle grade recycled PET

The 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 Tc, the enthalpy of crystallization ΔHc and the degree of crystallinity Xc 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 Zt 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.