ORGANIC ADDITIVES

    The primary group of organics tested were the cationic quaternary ammonium bromides, "QAB's" - particularly those with aliphatic chain-lengths of 12, 14 (cetrimide) and 16 (cetavlon). Also tested were the common anionic detergent, (sodium) dodecylsulfate, "SDS", and, as a comparison, the cationic antibiotic streptomycin (sulfate). Our focus was centered upon detergents since they would dissolve in both water-based and "oil"-based paints and varnishes.

    The detergents were first dissolved in isopropanol and then mixed into the liquid coatings. (The dry powders of these do not dissolve rapidly in the coatings themselves; thus the need for pre-dissolving them in a volatile base.)

    These were all given timed tests for a range of concentrations.

    RESULTS: Effectiveness was judged as being able to produce a sterile surface within 15 minutes of dampening with silty water. Streptomycin and SDS were found completely ineffective. QAB-12 was found to be about 5-times more rapidly effective than cetrimide (one fifth the concentration (w/v) was necessary to produce a sterile surface in 15 minutes). However, QAB-12 is much more than 5-times the price of cetrimide, thus it is not viable economically. Cetrimide was about twice as effective (w/v) than cetavlon, and their prices are about the same. Thus we find cetrimide the best product tested in all the various coatings. It's minimum effective concentration was 0.25% (w/v). Figure 6 shows the results of cetavlon.

    As shown on the touchable display sample at the poster site (Fig. 8; not shown here), cetavlon had little effect on color or texture of clear polyurethane on white PVC pipe.

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