The effect of the interfacial assembly of nano-silica in poly(lactic acid)/poly(butylene adipate-co-terephthalate) blends on morphology, rheology and mechanical properties

This work studies the effect of the interfacial assembly of spherical nano-silica particles on the morphology, rheology and mechanical properties of heterophase poly(lactic acid), PLA, and poly(butylene adipate-co-terephthalate), PBAT, blends. Through a controlled mixing strategy, nano-silica particles could be assembled in a stable fashion at the PLA-PBAT interface. Rheological analysis indicates that the interfacial assembly of nano-silica significantly diminishes the relaxation of the dispersed PBAT phase and 3 wt.% of nano-silica particles shifts the co-continuity region to a tower PBAT volume fraction. At co-continuity, the assembly of nano-silica at the interface changes the rheological behaviour of the co continuous PLA/PBAT from a liquid-like to a gel-like behaviour. The interfacial assembly of nano-silica reduces the co-continuous phase size but maintains co-continuity. The results of thermal annealing indicate a remarkable stabilization effect of interfacially assembled nano-silica on the co-continuous morphology. A conceptual model is proposed to explain the observed effects of interfacially assembled nano-silica on the morphology which emphasizes the critical role of nano-silica content, the relaxation time of the dispersed phase and the migration time of nano-silica to the interface. The mechanical properties of the PLA/PBAT blends are clearly influenced by the observed shift in co-continuity in the presence of nano-silica. Most importantly, the mechanical properties of co continuous PLA/PBAT are very sensitive to annealing due to morphological coarsening. Interfacially assembled nano-silica has the effect of completely stabilizing the co continuous morphology without any diminishing of the mechanical properties. These results clearly indicate the significant potential of the interfacial assembly of nano particles as a promising strategy toward achieving polymer blends with highly robust and stable co-continuous morphologies. (C) 2016 Elsevier Ltd. All rights reserved.