Rheology of PLA/regenerated cellulose nanocomposites prepared by the pickering emulsion process: Network formation and modeling

Abstract

PLA/regenerated cellulose (RC) nanocomposites containing 0.5, 1.0, 1.5, 2.0, 3.0 and 5.0 wt% cellulose were prepared by the Pickering emulsion process. The structure and the rheological properties of the composites were characterized by microscopy, the measurement of melt flow rate and oscillatory rheometry. Viscosity was modelled with the modified Carreau-Yasuda and the modified Cross models, and a new model was proposed as well. The results show that RC is a suitable reinforcement for PLA and the Pickering emulsion process produces homogeneous material. Good dispersion and the relatively large aspect ratio of the cellulose nanofiller leads to the formation of a network structure already at small cellulose content. Viscosity increases rapidly with increasing cellulose concentration and a yield stress appears already at 0.5 wt% RC content. Modeling helps the quantitative analysis of the experimental results and offers additional information about the structure and properties of the composites studied. All three models predict yield stress well, but only the new model gives reasonable values for the power law exponent. Other parameters and their composition dependence are difficult to interpret.

Keywords

• Melt rheology
• Oscillatory measurements
• Cellulose nanofibers
• Aggregation
• Carreau-Yasuda model
• Cross model