Effect of the Addition of Hydroxypropyl Methylcellulose and Hydroxyethyl Cellulose on the Rheological Properties and Thermogravimetric Kinetics of Dried and Redispersed Microfibrillated Cellulose

Abstract

Hydroxypropyl Methylcellulose (HPMC) and Hydroxyethyl Cellulose (HEC) were added in variable amounts (5–30% w/w) to microfibrillated cellulose (MFC) and after homogenization the blends were dried by spray drying and redispersed by sonication. The dispersions were characterized through oscillatory rheometric measurements, where amplitude, frequency and viscosity sweeps were performed. For redispersed blend samples, when compared to redispersed MFC and never-dried blends, the addition of HPMC and HEC resulted in an increase in storage and loss moduli, an increase in apparent viscosity and thixotropy, as well as greater stability. The use of sonication also showed significant effects for never-dried MFC suspensions and their blends, with increased moduli and viscosity. Furthermore, the dry blends in a ratio of 70:30 were studied for thermal stability and thermogravimetric kinetics, where interactions between the polymers were confirmed. The results showed a decrease in thermal stability and activation energy of the blends, which is probably a result of the decrease in cellulose intrachain and interchain hydrogen bonds.