What do the chemical and physical criteria mean and how does the chemistry work on stain-resistant carpet? Simply put, high pH levels (alkaline), high temperatures and/or cationic (positively-charged) cleaning chemicals can affect the integrity of stain-resistant treatments. And, high residual moisture levels may make it easier for the stain-protection system to be compromised. A brief look at how fibers and dyes work will help explain this further.
Stain-resistant chemicals are polymers – large molecules made up of colorless, carpet cleaning chemicals dye-like monomers; thus, polymers are larger than dye molecules. Fibers are made of nylon polymer chains that open and expand in the presence of hear and/or water.
Small water and dye molecules can enter the fiber easily, but the large molecules of stain-resistant chemicals have more difficulty 
penetrating the nylon. Thus, dyes penetrate far into the fiber, while the stain-resistant chemicals stay just inside the fiber’s surface.
Stain-resistant molecules are negatively-charged (anionic) particles; if positively charged, particles are called cations. Two particles of the same charge repel one another, but an anion and cation attract and neutralize one another.
Cleaners Must Be Anionic
When a stain molecule, which is an anionic dye, meets the anionic stain-resistance in carpet, it is repelled. On the other hand, if a large concentration of cations, such as a cleaner or topical treatment, comes in contact with the carpet, it is attracted to the stain resistance, neutralizes it, and the carpet loses its ability to repel the anionic stains it was warranted against.
Low Temperatures Required
Since water and heat are necessary to open up nylon fiber, so that dyes and stain-protection treatments can enter, excessive use of water and heat also can cause the escape of the treatments. The higher the temperature (heat), and the higher the amount of water left after cleaning, the more the fiber enlarges; stain-resistant molecules then can escape. The lower the temperature and the residual moisture, the less the potential for compromising the stain protection.
The pH Threshold
The pH of a solution, whether it’s the dyebath at the mill or a professional cleaner’s cleaning solution, can cause both dye and stain-resistant molecules to go in or out of fiber. These molecules, when in a low-pH (acid) solution, are pushed into the fiber. When the solution is alkaline (high pH), stain-resistant chemicals are drawn out of the fiber and into the solution. Research demonstrates that the upper limit of a cleaning chemical’s pH should be nine.
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