TEMPO-CNF suspensions in the viscoelastic regime: capturing the effect of morphology and surface charge with a rheological parameter

TEMPO cellulose nanofibril (TEMPO-CNF) suspensions in the viscoelastic regime are often used as rheological modifiers and additives to prepare composites and hydrogels. Therefore, understanding their rheology is important, including the role of morphology and surface charge. The viscosity of TEMPO-CNF suspensions decreases with higher homogenization pressure or number of homogenization passes, and higher surface charges. To compare the effects of morphology and surface charge more robustly, a rheological flow index parameter is developed. Zero-shear viscosity eta(0) is first determined from the Cross model, and the flow index k is defined through the scaling relation log(10)(eta(0))=k center dot c-log(10)(eta(water)), c being concentration and eta(water) the viscosity of pure water. The flow index decreases with higher homogenization energy and higher surface charge. The flow index condenses many viscosity points into a single parameter, establishing a clear and concise one-to-one relationship between TEMPO-CNF rheology and fibril characteristics, which can be used for quality control and/or benchmarking. [GRAPHICS] .

Automated summary

The viscosity of TEMPO-CNF suspensions decreases with higher homogenization pressure or number of homogenization passes, and higher surface charges. By developing a rheological flow index parameter, a clear and concise one-to-one relationship can be established between TEMPO-CNF rheology and fibril characteristics, which can be used for quality control and benchmarking.