I made solutions of Guar, PEO, and PAM in distilled water and then recorded the apparent viscosity over time for 40 days, to get an idea of how quickly the solutions degrade. For each polymer I made one solution with 0.02% Propyl Paraben and one without. Propyl paraben is used as a food preservative and considered effective against bacteria, yeasts, and fungi, over the pH range of these solutions. I speculated that it could prolong the effective life of the polymer mixes.

The Guar was at 6 g/L, the PEO (WSR-301) at 4 g/L, and the PAM at 1 g/L. The Guar and PEO were slurried using 10mL of denatured alcohol per gram of polymer, and all the solutions were mixed using a relatively low shear rate paint mixer. Apparent viscosity was measured as the drainage time (seconds) through a Ford #4 viscosity cup at approximately 1 hr, 2hr, 12 hr, and 24 hr after mixing each solution, then daily, then every 2 days. PEO and PAM are self siphoning and cannot be poured so I used a syringe to fill the viscosity cup - see photo. PAM hydrates very slowly so it was not possible to get a meaningful reading until after about 4 hours. All solutions were stored, tightly covered, at a fairly constant temperature of 21-22 degrees C (70-72 F).

The first graph uses the same scales on the y-axis and the second one uses exaggerated scales so variations stand out more and has smooth curves fitted. Within a week the Guar mixes had degraded, but Edward pointed out that bubble juices made using guar can keep for longer than a few days, so I started a new Guar mix at the same 6 g/L but with 15% Dawn by volume to see if the detergent prolonged the life of the guar - which does appear to b the case. The size of the error bars is a good indication of the uniformity of the mixes and they do suggest that it may not be possible to get a uniform mix at this concentration with the PAM using a low shear rate stirrer.

For those of you who are interested, the code to generate the graphs was written in 'R' using the package 'ggplot2'. A loess fit was used for the smooth curves.

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