Formaldehyde in Textiles:Detailed Analysis

Date: 2025/01/10 By: Zoe Zhu
What is formaldehyde?
The formaldehyde in textiles usually refers to the total amount of formaldehyde present in textiles, including formaldehyde, hydrolyzed formaldehyde and free formaldehyde. These formaldehydes may come from certain auxiliaries used in the production process of textiles, such as anti-wrinkle finishing agents, color fixatives, softeners, etc. The formaldehyde in these auxiliaries may be combined with fibers through chemical reactions, or exist in textiles in a free form. Excessive formaldehyde content may have adverse effects on human health. Therefore, different countries and regions have strict restrictions on the formaldehyde content in textiles.

Hazards of formaldehyde
1. Irritation: Formaldehyde is a very irritating gas. Long-term exposure to formaldehyde will cause conjunctival irritation, eye pain, conjunctival congestion, tearing, etc., and may also cause blindness in the long term.
2. Sensitization: Direct contact of the skin with formaldehyde can cause allergic dermatitis, pigmentation, necrosis, and inhalation of high concentrations of formaldehyde can induce bronchial asthma.
3. Mutagenic effect: High concentrations of formaldehyde are also a genotoxic substance. Inhalation of high concentrations can cause nasopharyngeal tumors.
4. Inhibition of bone marrow hematopoietic function. Formaldehyde can be absorbed into the bone marrow through the skin, gastrointestinal mucosa, etc., and inhibit the hematopoietic function of the bone marrow. In the long run, it may cause damage to the bone marrow function and even cause leukemia.

Sources of formaldehyde
In the textile processing process, formaldehyde mainly comes from the following seven aspects:
1 Anti-wrinkle finishing
Cross-linking agents containing formaldehyde are widely used in anti-wrinkle, anti-wrinkle and non-ironing finishing. In order to maintain the balance of formaldehyde, a certain amount of free formaldehyde will always be maintained in the finished product, otherwise it will affect the anti-wrinkle effect. Therefore, textiles and clothing that have been anti-wrinkle finished, whether they contain formaldehyde, low formaldehyde or ultra-low formaldehyde finishing agents, will always have a certain amount of residual formaldehyde on the cloth surface. Improper use will cause its concentration to exceed the allowable range.
2 Improve color fastness
formaldehyde in textiles can make the color of textiles bright and beautiful, and maintain the durability of printing and dyeing. The formaldehyde in children’s clothing mainly comes from dyes and auxiliary products that keep the colors of children’s clothing bright and beautiful, as well as adhesives used in clothing printing. Therefore, brightly printed clothing generally has a high formaldehyde content, while plain clothing without printed patterns has a lower formaldehyde content.

3 Dispersants
Disperse dyes and vat dyes are poorly soluble in water and are almost insoluble in water. Commercial disperse dyes contain a large amount of dispersants. The dispersants in disperse dyes can stably suspend the dye particles in the dye solution without sedimentation and agglomeration, and also have the effect of leveling. Diffusers are often used when dyeing with disperse dyes, such as diffuser NNO and diffuser N. Dispersants and diffusers are condensation products of naphthalenesulfonic acid or naphthalenesulfonic acid derivatives and formaldehyde. During the high-temperature and high-pressure dyeing process of disperse dyes, some formaldehyde will be released and remain on the fabric.
4 Pigment printing
In the pigment printing process, in order to improve color fastness, crosslinkers containing formaldehyde are often used, and the catalysts used in pigment printing often further increase the release of free formaldehyde. Even if high-quality formaldehyde-containing crosslinkers are used in the pigment printing process, it is almost impossible to meet the limit of 75mg/kg.
5 Stripping or bleaching reaction
Since Rongalite can make the dyed color disappear, it can generally be used as a resist for resist printing in the textile industry, and can also be used as a discharge agent. Textiles need to be steamed during the printing production process, and the steaming temperature is far above 60°C. If the printing auxiliary contains Rongalite, harmful gases such as formaldehyde will be released during steaming.
6 Waterproof and water-repellent finishing
A more durable waterproof effect is obtained by reacting unreacted hydroxy ether with cellulose or performing self-condensation. This compound requires a large amount of formaldehyde during the manufacturing process. Therefore, there will be a large amount of formaldehyde in textiles.

How is formaldehyde released?
The release of formaldehyde in textiles is mainly divided into three stages: free release, barrier release and chemical release.
Free release
In the early stage of release, the formaldehyde concentration on the surface of textiles is high, and free formaldehyde evaporates freely as gas at a fast rate.
Barrier release
As the release time increases, the formaldehyde in textiles concentration on the surface gradually decreases, and the formaldehyde physically deposited in the textiles or combined with the intermolecular force of the fiber gradually overcomes the resistance and diffuses outward, but this release is affected by the resistance and force of the textiles, and the diffusion rate is slow, and the volatilization amount gradually decreases.

Chemical release
It is mainly that the finishing agent fixed on the fiber undergoes a reversible reaction under certain conditions by cross-linking with the fiber, and releases formaldehyde in textiles to a limited extent until equilibrium is reached.
Prevention of formaldehyde
(1) Control by manufacturers. Currently, the formaldehyde content of non-ironing trousers, non-ironing shirts, paint-printed pajamas, etc. sold on the market exceeds the standard. In order to effectively control the excessive formaldehyde content in textiles and clothing, printing and dyeing factories producing fabrics are required to use green and environmentally friendly non-ironing finishing agents – formaldehyde-free finishing agents for non-ironing finishing as much as possible.
(2) Control of dyeing and chemical auxiliaries. Domestic auxiliaries manufacturers are required to speed up the development of environmentally friendly non-ironing finishing agents, which can improve the non-ironing effect and eliminate formaldehyde in textiles and clothing.

(3) Fabric manufacturers and clothing manufacturers should strengthen the washing process and post-treatment process before the products are shipped after anti-wrinkle finishing, so that the formaldehyde remaining on the fabric can be removed by water washing.
(4) Distributors should place the unpackaged textiles and clothing that have been non-ironing finished in a well-ventilated place to allow them to evaporate.
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