Evolution of Co-continuous Morphology along the Screw Length in a Co-rotating Twin-screw Extruder and Its Effect on Impact Strength of Compatibilized PA6/ABS Blend
An ultra-glide twin screw extruder is employed to allow the quick and easy removal of the screws from the fixed processing section within few seconds, probing the current degree of the melting state, the dispersive and distributive processing steps and finally the level of morphology development along extruder screws. For morphological studies the molten samples, collected from different points along the screw length, were quickly frozen in liquid nitrogen and observed under a scanning electron microscope. The morphology development along screws was studied for the compatibilized PA6/ABS blends with different ABS contents. It was observed that the co-continuous morphology was formed in an initial stage of mixing, which then transformed into a refined co-continuous structure and developed along the extruder. The level of co-continuity decreased at higher ABS content. In addition the effect of processing condition on morphology development was studied. In view of the mechanical properties, the effect of morphology on the impact strength could be elucidated. It was found that not only the co-continuous morphology but also the level of co-continuity plays an important role in determination of ultimate impact properties. The impact strength was lowered to 35 kJ/m2 from initial value of 47 kJ/m2 by increasing the ABS content from 60 to 70 wt%.