Effect of Capillary Diameter on the Rate of Radiation Induced Polymerization of Acrylamide in Saline Solutions Containing Dissolved Phosphorus-32.

Abstract

Radiation induced solution polymerization of acrylamide was studied at 80(DEGREES)C in tubes with diameters of 6, 2.29, 0.89 and 0.38 mm. The tubes were filled with aqueous solutions of 3% acrylamide, 10% NaCl and sufficient neutralized orthophosphoric acid to produce a specific radioactivity of 1 mCi/ml. of dissolved ('32)P. Distinctly higher initial rates of increase of solution viscosity were observed with increasing tube diameter. Kinetic studies were done also with 3% acrylamide in 0, 5 and 10% salt solutions at 81.5(DEGREES)C and 28(DEGREES)C; the reaction induced by external irradiation from ('60)Co. Other systems studied were 1 and 1.5% acrylamide in 0, 5 and 10% salt and 2% acrylamide at 28(DEGREES)C also under ('60)Co. The solutions at higher temperatures initially decreased in viscosity and then degraded as irradiation continued. No significant decrease in the solution viscosities with reaction time was observed in the solution polymerization of acrylamide initiated with K(,2)S(,2)O(,8) at 80(DEGREES)C, although the presence of salt reduced the maximum viscosity attained. The viscosities of the solutions irradiated at 28(DEGREES)C first increased with the absorbed dose, then stayed constant or decreased slightly, and if the initial monomer concentration were above a critical value, i.e. 1.5 2/v %, finally crosslinked. Pseudo-phase separation was observed during polymerization; the polymer tended to accumulate in the bottom phase. The presence of salt increased the rate of reaction and reduced the total dose needed for crosslinking. The relative viscosity vs. dose curves at 28(DEGREES)C for different salt contents coincided when plotted as relative viscosity vs. conversion. Solutions of polyacrylamide (0.2, 0.4, 0.6 and 1.0% in water and 0.1, 0.5 and 1.0% in 10% saline water) were also irradiated at 28(DEGREES)C with ('60)Co. A rapid decrease in viscosity of the samples was observed prior to gelation. The presence of salt delayed gelation. An expression for the extent of reaction as a function of dose (or time) and the size of the capillary containing the radioactive fluid was derived from the energy transfer characteristics of (beta) particles. It was also shown that conversion (x) vs. time (t) data for reactions in viscous media may be linearized on a -ln(l-x) vs. ln t plot. The applicability of the diameter dependence of reaction rate to selectively plug large channels in oil reservoirs was briefly discussed.