Characterization of spray-dried nanofibrillated cellulose and effect of different homogenization methods on the stability and rheological properties of the reconstituted suspension

Abstract

In the present study, a suspension of nanofibrillated cellulose from eucalyptus was spray-dried in order to obtain a powdered material that could be easily transported and stored. The original suspension and the dried material were characterized for their physical, morphological and thermal properties. An increase in crystallinity and reduction in thermal stability were observed after drying. In addition, the fibrils size passed from nano to micro scale The powder obtained was rehydrated and homogenized by two methods: rotor-stator homogenization (5000, 10,000 and 15,000 rpm) and ultrasound (10, 30 and 50% maximum amplitude), during 3 and 5 min, in order to verify the possibility of obtaining a stable reconstituted suspension comparable to the original one. Higher treatment intensities resulted in suspensions with higher viscosity and stability. The suspension homogenized by ultrasound at 50% amplitude for 5 minutes was the most stable one and restored the nano dimensions of the original suspension. Both the original and the reconstituted suspensions showed a shear thinning and “gel-like” behavior. Higher Ultra-Turrax speed and ultrasound amplitude resulted in higher viscoelastic modulus (G′ and G″), although these values were lower than those found in the initial nanocellulose suspension.