Rheological properties of microfibrillated cellulose and hydroxypropyl methylcellulose blends in ethanol/water solvent systems

Abstract Microfibrillated cellulose (MFC) and hydroxypropyl methylcellulose (HPMC) were synergistically employed as gelling agents in hydroalcoholic solutions. To investigate their collaborative effect, phase diagrams were constructed varying the concentration of the constituent elements, where phase formation was verified, as well as liquid-like and gel-like properties were identified through oscillatory rheometric measurements. Amplitude, frequency, viscosity and temperature scans were performed. Furthermore, aerogels were made with and without ethanol for microscopic analysis. It was demonstrated that ethanol has a great influence on the rheological characteristics of MFC and MFC + HPMC dispersions, resulting in an increase in the elastic modulus (G'), decreasing thixotropic behavior and increasing stability. HPMC promoted an increase in viscosity, a decrease in thixotropy as well as increased system stability. Tests were also carried out with urea, a strongly chaotropic agent, which provided evidence of the types of interactions that govern the systems, demonstrating that intermolecular hydrogen bond interactions play a preponderant role in the systems.