Development of nanocomposite films of poly(lactic acid) and bacterial cellulose by common melt processing techniques

BOVI, JIMENA; DOMINICI, FRANCO; BUTTO, MARTÍN; BERNAL, CELINA; FORESTI, MARÍA LAURA; PUGLIA, DEBORA

CABA

Congreso; WORLD CONGRESS OF CHEMICAL ENGINEERING 11; 2023

Asociación Argentina de Ingenieros Químicos

Poly(lactic acid) (PLA)-based composites filled with Kombucha-derived bacterial nanocellulose (BNC) were developed. BNC nanoribbons were isolated from the floating pellicle developed at the air-liquid interface during Kombucha tea production, and purified through a simple alkali treatment previously described [1]. Regarding the incorporation of the filler into the PLA matrix, three strategies were assayed: the direct introduction of oven-dried milled BNC (“PLA/BNC D”); the previous development of a masterbatch by solvent casting with a BNC concentration of 16.7 wt.% (“PLA/BNC MB”); and the elaboration of a masterbatch under the same conditions detailed before but using acetylated BNC (“AcBNC”, degree of substitution (DS)=0,15-0,2) instead of its native counterpart (“PLA/AcBNC MB”). Besides, two different processing techniques were compared: on the one hand, materials were melt compounded using an intensive mixer (Brabender; 170ºC - 50 rpm - 8 min) followed by compression molding (Carver; 170°C with no pressure - 8 min + 170°C - 2 MPa - 5 min) (“IM”); and on the other hand, extrusion in a twin-screw microextruder (DSM Xplore 5 & 15 Micro Compounder; 165-170-175ºC - 90 rpm - 3 min) (“E”) was assayed. In all cases, final filler concentrations were 1, 3, 5 and 7 wt.%.The development of masterbatches by solvent casting was conducted to improve the dispersion of the filler within the PLA matrix, since the oven drying of BNC leads to the irreversible aggregation of the nanoribbons compromising the distinguished properties related to their nanoscale. The surface hydrophobization of BNC nanoribbons through acetylation was also done to improve their compatibility with PLA and thus promote the dispersion of the filler [2]. As shown in Figure 1, “MB” composites exhibited a better dispersion of the nanocellulose than those obtained by direct introduction of the oven-dried BNC powder (“D”), for both processing techniques. Mechanical, optical and barrier properties of the films also highlighted the effects of both, the nanofiller incorporation strategy and the processing technique used.