Yellowing of waterproof nylon fabric mainly occurs in garment industry, because some softeners will cause yellowing of fabric due to ozone, and special anti-ozone softeners can reduce this problem.
In particular, cationic amino aliphatic softeners and some amine-modified silicon softeners (high nitrogen content) are very sensitive to high temperature oxidation, resulting in yellowing. The choice of softening agent and the required results must be carefully considered with the drying and finishing conditions to reduce the incidence of yellowing.
When exposed to high temperature, waterproof nylon fabric will turn yellow due to fiber oxidation, fiber and spinning lubricant, and impurities on fiber. Other yellowing problems may occur during the compression molding of synthetic fiber fabrics, and some anti-yellowing products are of great help to overcome these problems.
Generally speaking, fluorescent whitening agents have low sunlight fastness, and fluorescent whitening fabrics will gradually turn yellow if exposed to sunlight for too long. It is suggested that fluorescent whitening agents with high sunlight fastness should be used for fabrics with high quality requirements. Sunlight, as an energy source, will degrade fibers; Glass cannot filter all ultraviolet rays (only light waves below 320 nm can be filtered). Waterproof nylon fabric is very easy to yellow, especially semi-gloss or matte fiber containing pigment. This kind of photo-oxidation will cause yellowing and strength loss. If the fiber contains high water content, the problem will be more serious.
Cationic softeners will interact with anionic fluorescent brighteners, and reduce the whiteness of fabrics. The rate of reduction is related to the type of softeners and the chance of contacting nitrogen atoms. The influence of PH value is also very important, but the condition of strong acid should be avoided. If the PH of fabric is lower than PH 5.0, the hue of fluorescent whitening agent will turn green. If the fabric must be in acidic condition to avoid yellowing of phenol, the appropriate fluorescent brightener must be selected.