چكيده لاتين :
The ultrasonic degradation of polyethylene oxide (PEa) solutions was carried out
in water at 20, 25, 30, 35 and 40°C to investigate the effect of temperature and
solution concentration on the rate of degradation. Kinetics of degradation was
studied by viscometry. The obtained limiting molecular weights indicate that under the
conditions of increased temperature and solution concentration the degradation rate
of PEa solutions decreases. The obtained limiting molecular weights were correlated
in terms of concentration and temperature. The calculated rate constants also indicate
that degradation rate of PEa solutions decreases as the temperature and solution
concentration are increased. The calculated rate constants were correlated in terms of
concentration, temperature, and molecular weight of polymer. This degradation behaviour
was interpreted in terms of vapour pressure of water, viscosity, and concentration
of polymer solutions. With increasing temperature, the vapour pressure of solvent
increases and as this vapour enters inside the growing cavitation bubbles there is a
reduction in collapsing shock due to the developed cushioning effect. As a result, the
rate of degradation decreases. As the solution concentration increases, the viscosity
increases, leading to reduced cavitation efficiency and therefore the rate of degradation
decreases.
