Study on Optimization of Method for Measuring the Content of Potassium Salt of Polyacrylamide in Drilling Fluids

The potassium salt of polyacrylamide (PAM) is a widely used anionic polymer. In examining the quality of this polymer in accordance with the standard SY/T 5946—2002, several factors affect the final results, for example, the purity of the polymer is affected by inorganic salts existed in the process of examination, sodium nitrate used to measure the intrinsic viscosity is a kind of easy-to-explode substance and requires high level of control, and there is a big error in the determined chloride ions concentration. The procedure of examining the quality of the potassium salt of PAM was modified in our laboratory experiment. In measuring the purity of the polymer in laboratory, ethanol and hydrochloric acid as the washing liquid. The temperature and time for residue ignition were optimized. Sodium chloride was used to replace the sodium nitrate in measuring the intrinsic viscosity. In measuring the chloride ions content, the treatment of the sample was optimized and the pH of the sample was measured with titration method. All these measures helped improve the accuracy of the examination. It was found in the experiment that by adding 1.5% hydrochloric acid in the pure washing liquid, the solubility of the inorganic salt in the sample was increased, and the parting rate of the purity of the sample was thus increased by 40%. The residue of the sample was ignited at 800 ℃ for 3 hours, in so doing the real effective content of the sample can be measured. When using NaCl to replace NaNO₃ in the measurement of the intrinsic viscosity, the range of variation of the results was (00.40)/100 mL/g. In the measurement of chloride ions concentration, the sample was ignited at elevated temperatures and the pH value of the titration solution was adjusted, thus the variation of the results between parallel measurements was reduced from 1.02% - 1.73% to 0.0018%. These optimization measures help improve the accuracy and precision of the measurement, providing an effective base for examining the product quality of the potassium salt of PAM.