Degradation of polyacrylamide in dilute solution

The degradation of polyacrylamide in aqueous solution was investigated experimentally from the point of view of developing the polymer solution as a drag reducing fluid in district heating systems. Aqueous 200 wppm solutions of polyacrylamide were subjected to turbulent pipe flow to induce degradation. The Reynolds number was between 15 000-35 000 and the temperature was in the range of 15-70°C. To assess the degradation of the polymer, the friction factor vs Reynolds number was monitored. The results show that, in high shear flow, the degradation is caused not only by scission of polymer chains but also by a radical propagation reaction initiated by scission of polymer chains. This was confirmed by adding sodium sulfite, which effectively suppressed the degradation.