Manipulating the morphology of fully bio-based polymer blends through nanoparticles-heat resistant formulation based on poly(lacti acid)

A fully bio-based blend with Poly(lactic acid) (PLA) as the dominant component with improved high temperature creep resistance has been designed. The poor mechanical properties of amorphous PLA above its glass transition (~55°C) have been corrected by blending it with Polyamide 11 (PA11), a semicrystalline bio-based polymer, and promoting the continuity of the latter phase through the addition of small amounts of organo-modified montmorillonite (OMMT). The selective positioning of the filler inside the PA11 and at the PLA-PA11 interface has been exploited to convert the drop-matrix morphology of a blend at 70 wt.% of PLA into a stable co-continuous one. In such a way, a remarkable improvement of the high temperature mechanical performances has been achieved owing to the OMMT-rich PA11 framework, which interpenetrates the PLA and contribute to bear stresses up to ~160°C. The diverging relaxation times of the filled PA11 is believed to play the key-role in preserving the interpenetrated morphology attained during melt mixing [1]. Looking for optimized formulations, we have found that lowering the PA11 content results in the loss of the high temperature creep resistance, whereas increasing the OMMT content in the blend at 70 wt.% of PLA may bring about an excessive material embrittlement at room temperature.