Influence of ultrasonic parameters on degradation of acrylic acid/acrylamide copolymer based superabsorbent hydrogels cross-linked with NMBA

Continuous exposure to high-energy ultrasonic waves depolymerizes macromolecules in solutions and produces a permanent reduction in viscosity. Different factors affect the efficiency of this process. In this study, ultrasonic degradation of one commercially important hydrogel based on acrylic acid and acrylamide cross-linked with N,N-methylenebisacrylamide (NMBA) was carried out in aqueous solution at room temperature (25?°C). The purpose of this study was to present new experimental data for this ultrasonic degradation. In this respect, the effect of sonication parameters (power and pulse) on the rate of degradation was investigated. Granule disintegration was determined using a method to measure the swelling power of hydrogel. A method of viscometry was used to study the degradation behavior of the hydrogel and a first-order kinetic equation was employed to calculate the degradation rate constants. The experimental results indicated that the rate of ultrasonic degradation increased with increasing ultrasonic power and pulse. FTIR and UV spectrometry measurements confirmed that the degradation proceeded by mechanical forces. A detailed degradation mechanism has been proposed including chain scission. The present study has enabled us to understand the role of the ultrasonic parameters in deciding the extent of viscosity reduction in hydrogel systems.