Xanthan Stability at Elevated Temperatures

This paper examines xanthan stability to define the polymer’s temperature limitations as a mobility-control agent. Experiments probed the relative importance of hydrolysis, oxidation, and helix-coil transitions in xanthan degradation. In the absence of dissolved oxygen, free-radical oxidation/reduction reactions are not the dominant degradation mechanism. Depending on pH, acid-catalyzed hydrolysis and base-catalyzed fragmentation reactions may play important roles. Using Arrhenius calculations, under ideal conditions — no dissolved oxygen, pH 7–8, and moderate-to-high salinities — xanthan is estimated to maintain at least half its original viscosity for 5 years if temperature does not exceed 75–80°C. Above this temperature, new polymers are needed for chemical floods requiring mobility control.