Analysis of The Causes of Fabric Yellowing And Corresponding Measures

White or light-colored textiles made of nylon and elastane fibers and their blends are particularly susceptible to yellowing, which can occur during the dyeing and finishing process, in storage or hanging in store windows, oreven at home. There are many possible causes of yellowing, such as the fibers themselves, which are susceptible to yellowing (material-related), or the chemicals used on the fabric, such as residues of oils and softeners(chemical-related).

Often further analysis is required to determine the cause of yellowing, how the processing conditions are set up, which chemicals should be used or only which ones, what influences interact to cause yellowing, how the fabric is packaged and stored, etc.

Causes of fabric yellowing:

Gas fading

--NOx fumes from sizing machines

--NOx fumes from storage

--Ozone exposure

Temperature:

--High heat molding

--High temperature molding

--Softener and high temperature treatmen

Packaging & Storage:

--Phenol and amine related yellowing (Light):

--Fading of dyes and fluorescent essences.

--Degradation of fibers

Micro-organisms:

--Damage by bacteria and mold

Miscellaneous:

--Interrelationship between softeners and fluorescents.

Analysis of the source of the problem or countermeasures

Molding machine

There are several different types of styling machines used in the textile industry, either directly heated by burning gas and oil or indirectly heated by hot oil. Combustion-heated stylers produce more harmful NOx because the heated air is in direct contact with the combustion gas and fuel oil, while oil-heated stylers do not mix the combustion gas with the hot air used to set the fabric.

Avoiding the excess NOx created by directly heated stylers during high temperature styling can often be eliminated by using our SPANSCOUR.

Smoke discoloration and storage

Certain fibers and packaging materials, such as plastics, foam, and recycled paper, are processed with phenolic antioxidants, such as BHT (Butylated Hydroxy Toluene), which reacts with NOx fumes in stores and warehouses, which are caused by air pollution (e.g., including air pollution caused by traffic). These NOx fumes come from air pollution (including, for example, from traffic).

This problem can be avoided by avoiding the use of BHT-containing packaging materials and by keeping the pH value of the fabrics below 6 (by using fiber-neutralizing acids). The problem of phenol yellowing can be avoided by applying anti-phenol yellowing treatment during the dyeing and finishing process.

Ozone discoloration

Ozone discoloration is mainly a problem in the garment industry because some softeners can cause yellowing of fabrics due to ozone, and special ozone-resistant softeners can minimize this problem.

In particular, cationic amino-aliphatic softeners and some amine-modified silicone softeners (high nitrogen content) are very sensitive to high temperature oxidation, thus causing yellowing. The choice of softener and the required end result must be carefully considered together with the drying and finishing conditions in order to reduce the chance of yellowing.

High temperature

Exposure of textiles to high temperatures can cause yellowing due to oxidation of the fibers, fiber and spinning lubricants, and impurities on the fibers. Other yellowing problems can occur when synthetic fabrics are press-molded, especially for women's intimate apparel (e.g. PA/EL bras). Some anti-yellowing products are extremely helpful in overcoming such problems.

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