Nanofibrillar green composites of polylactide/polyamide produced in situ due to shear induced crystallization

Abstract

Nowadays, extensive efforts are devoted to develop efficient ways to prepare in-situ fibrillated polymer-polymer nanocomposites which are both strong and ductile. Using entirely bio-sourced polymers is essential to keep a green nature of the obtained nanocomposites. In current work, sustainable in-situ green nanocomposites of polylactide (PLA) and biosourced polyamide (PA) were obtained in one stage of extrusion through applying high shear rate. The critical role of a high shear rate in the possibility of implementing two simultaneous processes, namely, the transition from droplet to fibrillar morphology and the subsequent instantaneous stabilization of the formed fibrillar morphology via the shear induced crystallization of minor phase, is highlighted. It is shown that in the case of PLA/PA blend, both of these processes are activated at a shear rate of 300 s−1 and lead to the formation of nanofibers with nanosized scale (150–550 nm) and aspect ratios of 45. At a low concentration of PA, 5 wt%, this results in the formation of an effective nanofibrillar network, which leads to strong interfacial adhesion between the phases. The Young's modulus, strain at break and impact strength of in situ generated PLA/PA composite undergoes an enhancement nearly 7, 4500, and 90%, respectively, while its tensile strength retains high.