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Polylactic acid (PLA)/linear low density polyethylene (LLDPE) blend nanocomposites based on two different commercial-grade nanoclays, Cloisite® 30B and Cloisite® 15A, were produced via different melt mixing procedures in a counter-rotating twin screw extruder. The effects of mixing sequence and clay type on morphological and rheological behaviors as well as degradation properties of the blends were investigated. The X-ray diffraction (XRD) results showed that generally the level of exfoliation in 30B based nanocomposites was better than 15A based nanocomposites. In addition, due to difference in hydrophilicity and kind of modifiers in these two clays, the effect of 30B on refinement of dispersed phase and enhancement of biodegradability of PLA/LLDPE blend was much more remarkable than that of 15A nanoclay. Unlike the one step mixing process, preparation of nanocomposites via a two steps mixing process improved the morphology. Based on the XRD and TEM (transmission electron microscopic) results, it is found that the mixing sequence has a remarkable influence on dispersion and localization of the major part of 30B nanoclay in the PLA matrix. Owing to the induced selective localization of nanoclays in PLA phase, the nanocomposites prepared through a two steps mixing sequence exhibited extraordinary biodegradability, refiner morphology and better melt elasticity.

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 anddistributive 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%.