Carboxylation of polypropylene by reactive extrusion with functionalized peroxides for use as a compatibilizer in polypropylene/polyamide‐6,6 blends

Abstract Variable quantities of functionalized peroxides bearing carboxylic acid groups were reacted with polypropylene (PP) in a twin‐screw extruder. Systematic variations in the molecular structure of the peroxides were found to significantly affect the grafting efficiency of the carboxylic acid group onto the PP backbone, as well as affect the polymer degradation process. This behavior was attributed to the relative reactivities of the different free radicals generated by thermal decomposition of the peroxides. Furthermore, the functionalized polypropylene (f‐PP) was investigated as a compatibilizing additive for 80/20 PP/PA‐6,6 (polyamide 6,6) blends. With incorporation of the f‐PP into the blends, differential scanning calorimetry (DSC) showed an 80°C decrease in the PA‐6,6 crystallization temperature. A near linear increase in the impact strength of the blends was observed with f‐PP incorporations up to 30% of the PP phase. Moreover, blends containing 30% f‐PP demostrated impact properties approaching that of pure PA‐6,6.