Rheological Properties and Processing of Polymer Blends with Micro- and Nanofibrillated Cellulose

Abstract

Recently, scientists have a high interest in using micro- and nanofibrillated cellulose (MFC/NFC) fibers as reinforcing components in nanocomposites together with a biopolymer matrix. This interest is abstracted from the abundant availability of cellulose in nature and the need for renewable resources. Besides chemical aspects, however, the successful formulation of polymer blends with nanocellulose additives requires a good understanding of the physical compounding and mixing properties. Therefore, the rheological features of aqueous MFC and NFC suspensions play an important role for the further development of industrial applications. Generally, the MFC/NFC suspensions show nonlinear behavior in the form of a pseudoplastic or dilatant fluid at higher shear rates. There are different parameters affecting their rheological behavior including processing parameters, such as degree of fibrillation and concentration, and rheometrical parameters, such as shear rate, temperature, rheometer geometry (gap), wall slip, and flocculation. Controlling these parameters is very important before and after the processing of MFC or NFC due to the direct or indirect effects on the viscosity of the suspension. The aggregation of fibrillated cellulose is a conventional barrier to obtain suitable dispersive mixing and an important reason for the loss of mechanical properties of nanocomposites. As outlined in this chapter, better physical understanding of the rheological behavior of MFC or NFC is helpful for further processing of polymer blends by melt extrusion, injection molding, or electrospinning. A better rheological insight helps to control the processing of nanocomposites and avoid the named issues.