PLA/PA Bio-Blends: Induced Morphology by Extrusion

The effect of processing conditions on the final morphology of Poly(Lactic Acid) (PLA) with bio-based Polyamide 10.10 (PA) 70/30 blends is analyzed in this paper. Two types of PLA were used: Commercial (neat PLA) and a rheologically modified PLA (PLA(REx)), with higher melt elasticity produced by reactive extrusion. To evaluate the ability of in situ micro-fibrillation (μf) of PA phase during blend compounding by twin-screw extrusion, two processing parameters were varied: (i) Screw speed rotation (rpm); and (ii) take-up velocity, to induce a hot stretching with different Draw Ratios (DR). The potential ability of PA-μf in both bio-blends was evaluated by the viscosity (p) and elasticity (k’) ratios determined from the rheological tests of pristine polymers. When PLA(REx) was used, the requirements for PA-μf was fulfilled in the shear rate range observed at the extrusion die. Scanning electron microscopy (SEM) observations revealed that, unlike neat PLA, PLA(REx) promoted PA-μf without hot stretching and the aspect ratio increased as DR increased. For neat PLA-based blends, PA-μf was promoted during the hot stretching stage. DMTA analysis revealed that the use of PLA(REx) PLA(REx) resulted in a better mechanical performance in the rubbery region (T > Tg (PLA-phase)) due to the PA-μf morphology obtained.