Molecular weight degradation and rheological properties of schizophyllan under ultrasonic treatment

•Average molecular weight of SPG decreased significantly after ultrasonic treatments.•SPG and USPG fractions had pseudoplastic and near-Newtonian flow behaviors, respectively. Molecular weight degradation effects of schizophyllan (SPG) under ultrasonic treatments were investigated in this study. The degradation product was treated by alcohol fractional precipitation technology, and the molecular weight and rheological properties of ultrasonic-treated SPG (USPG) fractions were evaluated. Average molecular weight of SPG decreased significantly after ultrasonic treatments, and degradation product had more narrow distribution of molecular weight. The molecular weight degradation kinetics of SPG is adequately described by a second-order reaction. USPG fractions with different molecular weight were obtained by fractional precipitation for final alcohol concentration fractions 0–40%, 40–60% and 60–80%, respectively. USPG fractions had near-Newtonian flow behaviors, and USPG80% exhibited viscous responses over the entire accessible frequency range. Therefore, ultrasonic treatment is a viable modification technology for SPG and other polymer materials with high molecular weight.