Reaction of Polyacrylamide with Commonly Used Additives
Authors: Burcik Emil J. , Thankur Ganesh C. 
Published: December 2007

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In the past, several investigators have added formaldehyde as a bactericide to "pusher type" mobility control solutions. These investigators probably observed a decrease in resistance factor with time and attributed it to bacterial degradation. A more recent paper claims that formaldehyde acts as an effective paper claims that formaldehyde acts as an effective oxygen scavenger in polyacrylamide solutions. It states that low concentrations of HCHO are effective as a combination oxygen inhibitor and biocide, the oxygen inhibition being attributed solely to a reaction between HCHO and oxygen so that the latter is effectively removed from the system. The purpose of this note is to show that formaldehyde is a poor oxygen scavenger but that it probably reacts with the Pusher solution to form products that have properties quite different from the original proven Consequently, if formaldehyde is added to proven Consequently, if formaldehyde is added to a Pusher solution the behavior of the resulting system is not representative of the original polymer. This fact must be recognized if experimental results are to be interpreted intelligently. The following experiment clearly shows that a reaction occurs between formaldehyde and a typical Dow Chemical Co. Pusher. Two identical 500-ppm solutions of Pusher (700 type) were prepared in 2 percent NaCl. To one of them. 0.4 percent percent NaCl. To one of them. 0.4 percent formaldehyde (37 percent) was added immediately. After about 1 day of hydration at room temperature with intermittent slow stirring, the viscosity (Ostwald), the screen factor. and the pH were determined. These results are presented in the following table.

Pusher Pusher (0.4% (no formaldehyde) formaldehyde)

u(75deg. F), cp 1.90 1.92 Screen factor 12.40 12.70 pH 9.09 8.93

Each solution was also allowed to flow through a saturated, fine fritted glass filter disc (51, pore size) under a constant head, and the cumulative flow was measured as a function of time. The cumulative-flow vs time curves are shown in Fig. 1. where it can be seen that the solution containing formaldehyde completely plugged the fritted glass disc after the passage of about 19 cc. The other solution containing no formaldehyde propagated through the disc quite well. In other words, because of surface plugging the resistance factor exhibited by the polymer containing formaldehyde increased steadily from an initial value of 2.21 and eventually became infinite. The resistance factor of the polymer without formaldehyde was essentially constant (2.14 to 3.08) with throughput. It should be mentioned that both solutions were clear to the naked eye and no precipitate was apparent in the solution containing HCHO. Data for the same polymer solution containing only 0.1 percent polymer solution containing only 0.1 percent formaldehyde (therefore 370 ppm HCHO) are also shown in Fig. 1. The distinct curvature of the cumulative-flow vs time curve indicates a definite plugging action, but the effect is not nearly so plugging action, but the effect is not nearly so pronounced as in the case of the polymer containing pronounced as in the case of the polymer containing 0.4 percent HCHO.

P. 1137