Thermodynamic activation and ultrasound‑induced degradation dynamics of carboxymethyl cellulose (CMC)

Abstract

The research determined thermodynamic activation parameters for carboxymethyl cellulose (CMC) in water-based NaCl solutions through analysis of original high-molecular-weight CMC and its low-molecular-weight counterpart which resulted from ultrasound-induced degradation. The research team measured relative viscosity (ηr) of dilute solutions by testing different solution concentrations and temperature ranges. The research findings demonstrated that viscosity values experienced substantial changes when scientists altered solution concentrations and temperature levels. Scientists used Moore's technique which Arrhenius and Eyring equations helped them transform relative viscosity data into activation parameters which included the pre-exponential factor (A) and activation enthalpy (ΔH) and activation entropy (ΔS). The three parameters showed strong dependency on polymer concentration and solution viscosity and molecular weight. The high-molecular-weight CMC showed activation enthalpy and pre-exponential factor values which were higher than low-molecular-weight CMC but its activation entropy value was lower which means it resists flow better than low-molecular-weight CMC. The ultrasound-degraded CMC demonstrated better flow properties because its energetic obstacles became less difficult to overcome. The rising temperature caused viscosity to change in a non-linear pattern which also changed the activation parameters. The research team discovered how CMC flow behavior results from enthalpic and entropic factors while they showed ultrasound degradation effects on polymer solution behavior based on temperature and polymer concentration and molecule size