Blending of Immiscible Polymers in a Mixing Zone of a Twin Screw Extruder- Effects of Compatibilization

The dependence of the morphology development of physical as well as of reactivecompatibilized polypropylene/polyamide 6 (PP /PA6) blends in a mixing zone of aco-rotating twin screw extruder on blend composition and screw rotational speedwas investigated. A special process analytical set-up based on a co-rotating twinscrew extruder was used, which allowed melt sampling from different positionsalong the operating extruder in time periods less than 10 seconds. It has beenshown that the disperse particle sizes in physical blends depend crucially on theblend composition because of the increasing influence of coalescence with an increasingconcentration of the disperse phase. Furthermore, the morphology ofphysical PP/PA6 blends depends strongly on their rheological properties. In contrast,the influence of the screw rotational speed on the morphology is minor. Theresulting particle size in a mixing zone is achieved already after a short screwlength. The particle size of compatibilized blends is significantly smaller than inphysical blends because of the better conditions for drop break-up and the suppressionof coalescence effects. Due to this, compatibilization has a stronger influenceon the blend morphology than a variation of process or rheological conditionswith physical blends. Furthermore, the compatibilization leads to a concurrentcrystallization of the PA6 phase with the PP phase