With the development of the clothing industry, the new materials, new techniques as well as the washing process and post-treatment of the ready-to-wear products have witnessed increasing diversification.

You may have experienced the discoloration of the teeth and slider of the metal zipper (red copper, brass & copper-nickel-zinc alloy) or dye transfer of the fabrics during the washing or post-treatment process.

In this post, we will analyze the causes of the problems as well as the precautions that can be taken to eliminate or prevent the problems.

Discoloration Occurs With The Metal

As is known to all, the copper alloy will react with such chemicals as the acid, alkali, oxidizing agent, reducing agent and sulfide, which will result in the discoloration. Chemical reactions will take place easily between such chemicals or residues contained in the fabrics or introduced in the washing process and the metal parts of the teeth, slider, top & bottom stops and retaining box & pin, which will lead to the discoloration.

These reactions will take place easily in the high temperature and damp environment.  They will occur easily if the products are packed in the plastic bags immediately following sewing, washing and steam ironing, and stored in the bags for a long time. Chemical reactions will take place easily between the fabrics that involve reactive dyes and the copper alloy.

Discoloration Occurs With The Wool And Cotton Products Due To The Washing Process

Discoloration will occur if the zipper that contains copper alloy is attached to the wool fabrics which have been bleached.

Generally speaking, the following three methods can be applied to the bleaching of the wool.

• Processing using the oxidative bleaching agent (For example, Hydrogen Peroxide)
• Processing using the reductive bleaching agent (For example, dithionite)
• Chlorine treatment applied to the shrinkproof processing of the finished products (chlorinating agent in the chlorine group)

Chemical gases(for example, chlorine) will be introduced if the chemicals involved in the above-mentioned treatment methods (the second and the third methods in particular) are not fully cleansed or neutralized. In addition, the chemicals will react with the zipper surface in the damp environment. Discoloration will occur with the teeth, slider, top & bottom stops and retaining box & pin of the zipper that contains copper alloy due to the chemicals and gas volatilization if the finished products are packed in the bags immediately after ironing.

Tips

• The fabrics used should be fully cleansed and dried.
• The chemicals involved in the washing process should be fully cleansed and neutralized.
• Packing should be not performed immediately after ironing.

Discoloration Occurs With The Leather Products                                                            

Discoloration occurs due to the residues which result from the tanning agents and acids used in the tanning process of the leather.

Various tanning agents are involved in the tanning process of the leather, such as the mineral acid (for example, sulphuric acid), the tannic acid that contains chromium compound, the aldehyde compound, etc.

The leather is mainly composed of animal protein, whose liquids cannot be disposed of easily after the treatment. The contact between the residues and metal zipper will result in the discoloration of the metal due to the time and humidity factors.

Experiment Review
The contact between the genuine leather and zipper leads to the discoloration of the zipper teeth under the following conditions.
Temperature: 60℃
Humidity: 90%
Time: 72 hours

Tips

• The leathers used should be fully cleansed and neutralized after the tanning process.
• The clothing should be stored in the well-ventilated and dry environment.

Discoloration Resulting From The Sulfide

Sulphur dyes refer to the dyes which can be dissolved in sodium sulfide. They are mainly applied to the dyeing of cotton fiber and the blended textiles of cotton & fiber at a low cost. The sulphur black which is the main type of sulphur dye will react with the zipper teeth that contains copper alloy in the high-temperature and damp environment, resulting in the formation of copper(II) sulfide (black) and copper(II) oxide (brown).

Based on the test, it can be concluded that the discoloration results from the sulphur dyes involved in the fabrics.

Tips

• Attention should be paid to such factors as the temperature, testing time, PH value and the dosage of chemical agents.
• The clothing should be fully cleansed and dried immediately after the treatment.

Decolorization & Discoloration Occur With The Sewn Products Due To The Reactive Dyes Used

The reactive dyes applied to the dyeing of the cotton and hemp products contain metal ions. Reduction reaction will take place between the dyes and the copper alloy, which will result in the decolorization or discoloration of the fabrics. Discoloration will also occur with the zipper that contains copper alloy due to the reactive dyes involved.

Tips

• The clothing should be fully cleansed and dried immediately after the treatment. A strip of cloth could also be used to separate the zipper from the fabric.

Corrosion & Discoloration Resulting From The Application Of The Industrial Cleaning Pen

The industrial cleaning pen has witnessed wide application in the clothing industry, which is mainly used to dispose of the oil stain introduced in the sewing process. However, due to the strong acidity of the industrial cleaning pen, its contact with the zipper that contains copper alloy will result in the corrosion & discoloration of the latter.

Corrosion & Discoloration Resulting from The Dyeing/Bleaching Of The Ready-to-wear Products

On the one hand, dyeing is not applicable to the ready-to-wear products in the zipper industry as corrosion will occur with the metal parts including the zipper teeth, slider, retaining box & pin, etc. due to the chemicals involved. On the other hand, the bleaching treatment applied will also result in the corrosion of the fabrics and metal zippers.

Attention should be paid to the concentration of the bleaching agent. Besides, the temperature should be kept below 60° C.

Tips

• Sample dyeing should be carried out prior to the dyeing of the ready-to-wear products.
• The clothing should be fully cleansed and dried immediately after dyeing.

Conclusion

SBS zipper is currently working on better solutions to the above-mentioned issues. Please follow the tips below and consult with us if you have any questions.

• The products should be fully cleansed, dried timely and stored in the well-ventilated and dry environment.
• Sample tests should be carried out prior to the dyeing and bleaching of the ready-to-wear products.
• Investigations should be carried out into the discoloration and dye transfer of the zippers.