In-situ (Nano) fibrillation of biopolymer blends based on poly(butylene-adipate-co-terephtalate)/poly(lactic acid) (PBAT/PLA) : effect of ethan-1-aminium ionic liquids on rheological, mechanical and barrier properties
Résumé
The ionic liquids based on ethan-1-aminium salts associated with inorganic (perchlorate (ClO4−), tetrafluoroborate (BF4−) and dicyanamide (Dca)) anions have been used as new compatibilizers of biopolymer blends based on poly(butylene-adipate-co-terephtalate)/poly(lactic acid) (PBAT/PLA). To highlight the effect of the nature of the anions, 2wt% of ionic liquids (ILs) have been introduced within a PBAT/PLA blend (60/40 wt%) and the corresponding compositions have been processed in melt by twin-screw extrusion and injection molding at a processing temperature which was above the melting temperature of the PBAT matrix and below the peak melting temperature of the PLA dispersed phase. Under these conditions, the PBAT matrix remained as a melt, whereas the dispersed phase with the higher melting temperature (PLA phase) could deform into fibrous structure under the elongational flow. The thermal, rheological, mechanical and barrier properties of PBAT/PLA/ILs were systematically investigated to elucidate structure–rheology–properties relationships. Transmission electron microscopy (TEM) analyses revealed the presence of stable nanofibrillar morphology in the case of PBAT/PLA/ILs blends. The aspect ratio of PLA fibrils increased when ILs were used, especially with the presence of BF4– and Dca anions. The latter resulted in the greatest improvement of the rheological response of the blends due to their high aspect ratios and the ionic liquids induced network structure [1]. The mechanical properties analyses showed that the use of ethan-1-aminium ILs in PLA/PBAT blends induced a self-reinforcing effect with an excellent compromise between stiffness (Young's modulus) and ability to sustain large deformation (strain at break), especially for BF4– and dCa based anions. More interestingly, the addition of 2 wt% of ethan-1-aminium-based ILs induced a high decrease in water vapor permeability of self-reinforced PBAT/PLA/ILs nanofibrillar composites with a reduction factor of 10 in the case of BF4– anions. On the other hand, the oxygen permeability values were reduced in all PBSA/PLA/ILs blends, reaching reduction rates between 35 and 73 %. The results found in the present study highlight the potential role of ethan-1-aminium ILs as compatibilizers of polyester-based blends allowing to design PBAT/PLA blends displaying improved gaz barrier, rheological and mechanical performances, i.e. combining the intrinsic properties of PBAT and PLA coexisting phases. References [1] M. Yousfi, S. Livi, J. Duchet-Rumeau, Ionic liquids: A new way for the compatibilization of thermoplastic blends. 255 (2014) 1391–1398. https://doi.org/10.1016/j.cej.2014.06.080.