The state of carboxymethylated nanofibrils after homogenization-aided dilution from concentrated suspensions: a rheological perspective
2014 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 21, no 4, 2357-2368 p.Article in journal (Refereed) Published
The rheological properties of a carboxymethylated (D. S. & 0.1) nanofibrillated cellulose (NFC) were investigated at different solid contents. The critical overlap concentration was determined to be in the range between 0.04 and 0.07 % (w/w) using shear stress versus shear rate measurements. From the critical overlap concentration using the simple Mason excluded volume formalism, the apparent aspect ratio was estimated to be 75 [ at a critical overlap concentration of 0.04 % (w/w)]. The aspect ratio of the NFC system was also estimated by using the EinsteinSimha equation together with the intrinsic viscosity value of the system (corrected for the electroviscous effects). The obtained value was found to be around 80, which is in good agreement with the value obtained from the excluded volume calculation. Further, by combining oscillatory measurements and the equation of Shankar et al. the apparent fibril length was determined to be 4 mu m. As the production of NFC through homogenization occurs at concentrations far above the critical overlap concentration an NFC-gel is constituted by a severely entangled structure. The disentanglement of the fibrils is therefore difficult and the employed dilution method was found not to lead to fully liberated nanofibrils, which was also indicated by atomic force microscopy-imaging.
Place, publisher, year, edition, pages
2014. Vol. 21, no 4, 2357-2368 p.
Nanofibrillated cellulose (NFC), Carboxymethylation, Rheology, Homogenizer, Atomic force microscopy (AFM)
Polymer Technologies Materials Engineering
IdentifiersURN: urn:nbn:se:kth:diva-153272DOI: 10.1007/s10570-014-0329-9ISI: 000341490200014ScopusID: 2-s2.0-84904309327OAI: oai:DiVA.org:kth-153272DiVA: diva2:752980
QC 201410062014-10-062014-10-032014-10-06Bibliographically approved