Many clients express concerns about the safety of flame retardant finishes and their impact on garment durability when selecting protective workwear. This article provides a detailed explanation of whether flame retardant fabrics contain formaldehyde, the chemical properties of formaldehyde, and its effects on fabrics and finished workwear. It also offers guidance on how to choose high-quality products.
We previously received an inquiry from a customer who reported that the buttons on workwear made from flame-retardant fabric they had sourced were rusting. They asked why this problem occurred and how to solve it. After a brief communication, we quickly identified the cause and provided a solution.
First, let’s address some key questions about flame retardant fabrics:
1.Does After-Treated Flame Retardant Fabric Contain Formaldehyde?
The answer is: It might, but not necessarily. It depends on the type of flame retardant used and the finishing process.
Formaldehyde-Containing Flame Retardants:
Some durable flame retardant finishing processes (especially for cellulosic fibers like cotton or viscose) use nitrogen-phosphorus-based flame retardants. During the synthesis or cross-linking curing process of these retardants,
formaldehyde may be used as a reactant. Consequently, if the treated fabric is not thoroughly washed, it may retain a certain amount of free formaldehyde.
[Formaldehyde-Free Flame Retardants:]
[With stricter environmental regulations (such as EU REACH, OEKO-TEX standards) and technological advancements, a significant number of formaldehyde-free flame retardants have emerged on the market. For example:]
[Eco-friendly flame retardants based on phosphorus and nitrogen elements.]
[Many flame retardants designed for synthetic fibers (like polyester) are inherently formaldehyde-free.]
[Some physical after-treatments, like coating, may also use formaldehyde-free coating agents.]
[In summary: It cannot be generalized. Flame retardant fabrics compliant with international eco-standards (e.g., OEKO-TEX Standard 100) have their formaldehyde content strictly controlled at very low levels (e.g., <75mg/kg, or <20mg/kg for infantswear),]
[making them safe for humans. However, low-end or non-compliant flame retardant fabrics may carry a risk of excessive formaldehyde.]
2.Chemical Properties of Formaldehyde
(1) Strong Reducibility: Easily oxidized, can reduce silver ions, copper ions, etc.
(2) Electrophilicity/Addition Reactions: The carbonyl carbon exhibits electrophilicity, prone to addition reactions with nucleophiles (water, alcohols).
(3) Polymerizability: Gaseous formaldehyde readily polymerizes into a trimer or solid paraformaldehyde.
(4) Reaction with Nitrogen Compounds: Easily undergoes polycondensation reactions with urea, melamine, etc.
(5) Cross-linking with Proteins: Reacts with amino groups, thiol groups, etc., in protein molecules, forming stable methylene bridges, causing denaturation and solidification.
[It was historically used as anti-wrinkle and anti-shrinkage finishing agents for textiles (e.g., “non-iron” shirts) to maintain crispness.]
Next, let’s understand the impact of formaldehyde present in fabrics on the fabrics themselves and on finished FR workwear.
Impact on the Fabric Itself:
1.Strength Damage:
Excessive formaldehyde, particularly under acidic conditions, can catalyze the hydrolysis of fibers (especially cellulosic fibers like cotton or viscose), leading to decreased fabric strength and increased breakage rates. Garments might tear after minimal wear.
2.Yellowing:
Formaldehyde resin finishing agents or their decomposition products can cause white or light-colored fabrics to yellow, affecting appearance.
3.Impact on Sewing Thread:
Sewing thread (especially cotton thread) is also susceptible to hydrolysis by formaldehyde, leading to a significant decrease in thread strength. This is a very hidden yet critical hazard—the fabric and buttons might seem fine, but the seams could suddenly split and break.
4.Impact on Accessories:
Hook-and-Loop Fasteners (e.g., Velcro): Nylon-based fasteners can become brittle due to formaldehyde, leading to reduced grip or breakage.
Prints or Coatings: Excessive formaldehyde can cause chemical reactions, leading to cracking, peeling of prints, or stickiness/hardening of coatings.
5.Corrosion of Metals (e.g., Iron, Copper, Zinc Alloys):
Due to its strong reducibility, especially under specific conditions (high temperature, high humidity), water vapor in the air can form a thin film on metal surfaces.
>This water film absorbs and dissolves formaldehyde gas, forming a weakly acidic formaldehyde solution directly on the material’s surface.
>Once the water film forms, formaldehyde acts as an oxidant (reducing agent) within it, participating in the anodic oxidation process of the metal.
Using iron as an example:
Anodic reaction: Fe → Fe²⁺ + 2e⁻ (iron loses electrons and dissolves)
Cathodic reaction: 2H⁺ + 2e⁻ → H₂↑ or O₂ + 2H₂O + 4e⁻ → 4OH⁻ (formaldehyde participates in or promotes these reactions, consuming electrons)Formaldehyde’s reducibility disrupts the stability of the metal surface, continuously “pulling away” electrons, thereby accelerating metal dissolution (corrosion).
>This leads to rusting of iron fixtures, stubborn rust stains; oxidation, blackening, and loss of shine on copper or alloy zippers; and corrosion peeling of electroplated layers.
>It affects aesthetics, stains clothing, and can cause zippers to jam, malfunction, or even fail completely, significantly shortening the garment’s lifespan.
Without this water film, the corrosion process by formaldehyde gas is very slow or even negligible. In dry environments, the direct corrosion risk from formaldehyde to most materials is low.
6.Impact on Certain Plastics and Polymers:
Swelling and Aging:For some plastics (like ABS, certain polyurethanes, nylon), formaldehyde acts not through electrochemical corrosion but as a chemical solvent or reactive substance. It has a “solvent effect” on plastics like ABS or nylon, permeating the polymer chains. Long-term exposure can destroy the polymer chain structure, causing the plastic to become brittle, lose gloss, develop cracks, or even fracture—a phenomenon often called “environmental stress cracking.”
7.Impact on Storage and Packaging:
Inside packaging (especially sealed plastic bags), volatilized formaldehyde cannot dissipate, creating a high-concentration gaseous environment.
This greatly accelerates the corrosion and aging process of all components, including the fabric itself.
From communication with the customer, we learned their workwear was sold for use in coastal Southeast Asian countries, where temperature and humidity are high. We suspect the primary reason for the issue was high residual free formaldehyde content in the previously sourced flame-retardant fabric. When stored or used in highly humid environments, formaldehyde combines with moisture to form an acidic environment, corroding the metal buttons.
Based on the customer’s situation, we provided phased improvement suggestions for production and recommendations for post-production garment storage:
1.Production Phase:
We can control the factory production process to significantly reduce the formaldehyde content in the fabric, even down to <20mg/kg, making improvements right from the fabric stage. After fabric production, thorough washing can remove most free formaldehyde.
2. Buyer’s Choice of Accessories:
Recommend buyers choose buttons made of stainless steel, high-quality aluminum alloy, or buttons with dense, high-quality plating (e.g., heavy gold electroplating).
Choose plastic materials with good chemical stability, such as PP (polypropylene) or PE (polyethylene). Prioritize high-quality nylon zippers or stainless steel zippers for their stronger chemical corrosion resistance. Use 100% polyester flame-retardant filament sewing thread, which offers better acid and alkali resistance than cotton thread and is less prone to degradation by formaldehyde.
3.Controlled Storage Environment:
When storing textiles or items containing formaldehyde, ensure the environment is dry (humidity controlled below 50%), cool, and well-ventilated. Using desiccants and dehumidifiers is very effective.
If you encounter other issues with flame retardant fabrics or workwear, please feel free to contact us. We hope to find a solution for you and are happy to be of service.
Keywords: Formaldehyde, Flame Retardant Fabric, FR Fabric, Workwear, Corrosion, Metal Buttons, Zippers, Sewing Thread, Fabric Strength, Yellowing, Storage, OEKO-TEX.
