Tailoring the properties of PP/PA6 nanostructured blends by the addition of nanosilica and compatibilizer agents

The effectiveness of combining silica nanoparticles (NS) and polypropylene grafted with maleic anhydride (PPgMA) to stabilize the morphology and improve the properties of an immiscible PP/Nylon 6 blend was investigated. Blends of 80% polypropylene (PP) and 20% polyamide 6 (PA6) with a fixed amount of PPgMA and decreasing NS content were prepared by melt mixing. Two PPgMA compatibilizing agents with different grafting level and two modified NS, one hydrophilic and other hydrophobic, were employed. Used together, PPgMA and 4.0% of NS nanoparticles strongly reduced the PA6 droplet size, as a result of the preferential location of the NS at the interface avoiding drop coalescence. The effect was more remarkable when hydrophobic NS was added. Owing to the reduced droplet size, a fractioned crystallization of the PA6 dispersed phase was observed by DSC measurements, and self-nucleation experiments were carried out to elucidate the nature of the phenomenon. Despite the PA6 reduced size, the blends exhibited unsatisfactory mechanical performance. Thus, the NS content was decreased. In the end, a PP/PA6 blend stabilized with 1.6% hydrophobic NS and compatibilized with high grafting level PPgMA exhibited a fine-tuned morphology with enhanced ductility and barrier properties. NS nanoparticles act as outstanding stabilizers but do not promote interfacial adhesion between the phases. Therefore, the use of an optimal content of NS along with a compatibilizer yields a synergistic effect on the PP/PA6 blend. (C) 2016 Elsevier Ltd. All rights reserved.