Halogen-free Flame Retardant Modified Materials in The Construction Industry - Textiles

Halogen-free Flame Retardant Modified Materials in The Construction Industry - Textiles

1. Textiles and fire safety

In general, textiles are lightweight and contribute less fuel in a fire (“fire load”) than other organic materials. However, most textiles pose other fire risks, e.g., they catch fire easily, can spread flames, and are particularly capable of melting and producing dripping material. Essentially, the burning properties of textiles depend on the chemical composition of the fibers (natural or synthetic). Consequently, the burning properties of textiles not treated with flame retardants vary considerably when exposed to an ignition source (Tables 1 and 2).

Fiber-based materials may have inherent flame retardancy (e.g., PTFE fibers) or, alternatively, flame retardancy may be obtained by

1. Adding reactive flame retardants to the fibers.

2. Apraying a flame retardant onto the fibers.

3. Blending flame retardant additives into the fibers by melting.

Table 1: Fire performance of various fibers

Table 2: Polymer Flammability Index

2. Textiles for the Building and Construction Industry Overview

Textiles are used for decorative and/or functional purposes, and Table 3 summarizes the most common applications for textiles.

Table 3: Overview of textiles for the building and construction industry

3. Washing resistance of textile flame retardants and textile flame retardant treatments

Different textiles may need to be washed under different conditions, depending on the end use of the product. Flame retardants can achieve different degrees of wash resistance (as opposed to permanence of the flame retardant treatment):

• Non-durable: the flame retardant does not resist washing at all

• Semi-durable: textiles lose their flame retardancy after a limited number of washes or soaks

• Durable: textiles remain flame retardant after at least 50 washes in boiling water.

Different degrees of durability can be achieved by applying flame retardants in different ways.

• Non-durable flame retardant treatment

In a continuous process, textiles are immersed in a water bath containing a flame retardant solution and then, under controlled pressure, the textiles are squeezed between two rollers. This process deposits a predetermined amount of flame retardant onto the textile. The amount of flame retardant deposited must be sufficient to meet the fire performance requirements. The continuous process is then continued by drying the textile at a temperature range of 100°C to 160°C, depending on the material.

• Semi-durable flame retardant treatment

The treatment can be carried out in two ways:

- Weak cross-linking between special flame retardant salts and fibers: This method is usually limited to a few combinations of textile fibers with flame retardants, e.g. cross-linking of cotton fibers with specific flame retardants. After impregnation, the fabric is dried and the polymer cured.

- Application of the flame retardant in the back coating: In general, this method is suitable for all textiles and is only restricted if the surface structure of the textile is sensitive and the surface may be damaged during the flame retardant treatment. The flame retardant paste or foam as well as the bonding agent can be applied to the back side of the textile by means of an applicator roller or doctor blade system at a thickness that ensures that the required fire performance is achieved. The coating is then dried and the bonding agent undergoes a cross-linking reaction to give the flame-retardant coating the necessary durability, which essentially depends on the type and properties of the bonding agent.

• Durable Flame Retardant Treatment

Durable flame retardant treatments can be achieved by the following six techniques and processes:

- Cross-linking of reactants:

A stable chemical cross-linking is achieved between the substrate and the flame retardant, e.g. flame retardant treatment of cellulose fibers. In the treatment process, the flame retardant is first applied in solution form, followed by drying and curing. Before the final drying of the fabric, unreacted molecules are neutralized and then washed.

- Self-crosslinking:

Polymerization or polycondensation of the flame retardant on the substrate, e.g. flame retardant treatment of knitted or woven fabrics.

- Thermal fixation: the flame retardant is deposited within the fiber, e.g., post-treatment of polyester fibers.

- Transfer coating:

Flame retardant is coated on the surface of the paper to form a polymer film containing the flame retardant. The polymer film is laminated to the fabric prior to curing in a drying room. The flame retardant is permanently encapsulated within the polymer and is not removed by washing. When using this process, other features can be added within the textile (e.g., water repellency) or surface properties can be altered, e.g., in the manufacture of artificial leather.

- Ionic crosslinking:

Negatively charged complexes are bonded to positively charged alkaline groups, e.g., flame-retardant treatment of wool.

A flame retardant is supplied from a large bath ratio acidification masterbatch so that the flame retardant is ionically exchanged with the fibers. As a result, the negatively charged complexes flow out and adhere to the positively charged alkaline groups, culminating in ionic crosslinking.

- Production of fibers with inherent flame retardancy:

Such fibers are produced by:

I. Adding a flame retardant copolymer monomer during the polymerization reaction to produce flame retardant fibers, e.g., polyester fibers.

II. Designing polymer backbones with high heat resistance and high flame retardancy, e.g., based on poly(phenylidene-isophthalimide), polyamide-imide, poly(phenylene-terephthalamide) phenylterephthalimide, polytetrafluoroethylene (PTFE), and a few other polymers as polyarylamide fibers.

The techniques described above in relation to inherently flame-retardant fibers are more accurately described as polymer chemistry than as textile flame-retardant treatments.

Flame Retardant Additives by Melt Blending.

The addition of flame retardant additives to polymers (either alone or via masterbatch) prior to melt spinning is a well known technique for improving the fire resistance of textile materials.

4. Phosphorus and Nitrogen Inorganic Flame Retardants for Textiles

Table 4 below lists the most commonly used flame retardants in textiles for construction. With a few exceptions, different flame retardants must be used in combination in order to fulfill various requirements, including combustion performance requirements, as well as other performance requirements, such as functionality, wash resistance, hand feel (soft, hard) of the flame retardant-treated textiles.

Table 4: Flame retardants for textiles

5. Conclusion

YINSU Flame Retardant offers textile flame retardants that incorporate highly effective flame retardant additives evenly into fibers through advanced melt blending technology. This innovative approach not only enhances the flame retardant properties of textiles, but also ensures that the flame retardant effect is long-lasting and not easily degraded by washing or daily use.

YINSU's line of flame retardants includes non-halogenated flame retardants and red phosphorus flame retardant masterbatches. These products, such as PET-55D and PPET-70B White Flame Retardant Masterbatches, are known for their excellent flame retardant efficiency. They enable textiles to achieve the stringent V0 flame retardant rating, an important measure of a material's flame retardancy, at less than 10% addition. The homogeneous blend of these flame retardants with polyester raw materials is transformed into finished textile products with durable flame retardant properties through a fine drawing process.