Lo Re Giada (1)*, Cailloux J. (2), Raquez J.M. (3), Santana O. (2), Dubois P. (3), Maspoch M. Li (2)
(1) Chalmers University of Technology - Gothenburg - Sweden, (2) Universitat Politecnica de Catalunya Barcelona Tech - Terrassa - Spain, (3) University of Mons - Mons - Belgium
The present study intended to demonstrate the viability of the physical adsorption of PEG onto the surface of hydrophilic cellulose nanofibrils (CNFs), to enhance their dispersion within a hydrophobic PLA matrix through melt blending. For this purpose, CNF-reinforced PLA nanocomposites were manufactured via extrusion and injection moulding using an organic solvent-free PEG/CNF masterbatch approach, already successfully reported for macromolecular water-borne surfactants [1]. Here, it has been demonstrated that PEG adsorption onto the filler surface may serve as an effective way to protect CNFs against self-agglomeration during drying. In fact, both microscopy and rheology characterization techniques clearly evidenced a progressive refinement of the CNF dispersion within PLA upon increasing the PEG dosage in the initial aqueous PEG/CNF dispersion, [2]. With adding 20 wt.% of PEG, linear viscoelastic data at low frequencies revealed the formation of a rheological percolated network (yield stress in |*| and plateau region in G’), indicative of a successful CNF dispersion. All these led to a gradual increase in the PLA melt elasticity, which suggest a better processability in specific operations where it is the dominant factor (i.e. film blowing/casting, foaming). Thermo-mechanical characterization of the PLA/PEG/CNF samples revealed an effective reinforcement effect of the CNFs in the glassy as much as in the rubbery state. Finally, this simple and physical method constitutes an approach of choice for developing CNF-reinforced PLA nanocomposites through melt processing at the industrial scale.
Figure 1: Evolution of the minimum E’ value in the rubbery plateau for PLA samples () and PLA/enz-CNF bio-composites () as a function of the PEG content.
References
1. Lo Re, G.; Engstrom, J.; Wu, Q.; Malmström, E.; Gedde, U. W.; Olsson, R. T.; Berglund, L. A., Improved cellulose nanofibril dispersion in melt-processed polycaprolactone nanocomposites by a latex-mediated interphase and wet feeding as LDPE alternative. ACS Applied Nano Materials 2018.