Effect of capillary diameter on the rate of radiation induced polymerization of acrylamide in saline solutions containing dissolved 32P

Radiation induced solution polymerization of acrylamide was studied at 800C 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 32P. 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 81.50C and 280C; the reaction induced by external irradiation from 60Co. Other systems studied were 1 and 1.5% acrylamide in 0, 5 and 10% salt and 2% acrylamide at 280C also under 60Co. 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 K2S2O8 at 800C, although the presence of salt reduced the maximum viscosity attained. The viscosities of the solutions irradiated at 280C first increased with the absorbed dose, then stayed constant or decreased slightly, and if the initial monomer concentration was 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 280C for different salt contents coincided when plotted as relative viscosity vs. conversion. The applicability of the diameter dependence of reaction rate to selectively plug large channels in oil reservoirs was briefly discussed