Rheological characterization of high concentrated MFC gel from kenaf unbleached pulp

Abstract

Microfibrillated Cellulose (MFC) was isolated from unbleached kraft pulp derived from kenaf bast fiber. MFC gels with different concentrations were manufactured from pulp with varying initial consistencies. The MFC was diluted to a consistency of around one percent using distilled water and was further homogenized by passing through a microfluidizer. In order to gain an understanding of the relative changes in behavior of the resulting MFC gels, their rheological properties were characterized. Results show that all of the gels exhibit a shear-thinning behavior. It was also determined that the rheological characteristics improved with increasing gel concentration, which was achieved by using higher pulp suspension consistencies. Diluted MFC that was derived from highly concentrated MFC had more variable modulus under the same strain and frequency compared to poorly concentrated MFC. But such a strong effect was not observed for viscosity. Additionally, the value of G′, ranging from 76 to 5325 Pa under the studied concentrations, was found to be fourfold the value of G″. In the low frequency range, G′ was almost independent of frequency, but was dependent on gel consistency with a coefficient of 3, indicating that MFC gels are elastic. These results show that it is possible to produce MFC gels with good rheological properties from high consistency kenaf pulp suspensions.