Anti-UV Flame Retardant Fabrics and Textiles

Abstract. This article mainly introduces the importance of UV resistant fabrics, the principles and production processes of UV resistance, as well as the methods and indicators for evaluating the UV resistance performance of fabrics. BEGOODTEX combines UV protection technology into flame-retardant fabrics.

1. Overview

Classification and function of ultraviolet radiation

Apart from what we can see as light in the solar spectrum it also consists of ultraviolet and infrared light that cannot be seen with the naked eye. Ultraviolet light is a type of wave that has a shorter wavelength than visible light making up around 6 percent of the spectrum. The wavelength range for radiation falls, between 200 to 400 nanometers. Based on the wavelength and various biological impacts of radiation. It is categorized into three bands; UV A for 320 to 400 light waves; UV B for 290 to 320nm wavelength range; and UV C, for the range of 200 to 290nm.

The atmosphere’s protective layer known as the ozone layer is depleting due to the release of chlorofluorocarbons like Freon from human activities and daily routines in recent years. This thinning of the ozone layer has led to a rise in radiation reaching the Earth’s surface resulting in an increase in illnesses caused by excessive exposure, to UV rays. Typically regular clothing materials offer 50% protection against ultraviolet rays, which falls short of the necessary protective standards. Moreover prolonged exposure, to radiation can lead to fading and aging of fabrics. As a result,t it becomes essential to apply UV treatments to textiles.

Considerations for UV resistance of textiles

When sunlight hits the surface of a fabric; some bounces off it while some gets soaked in and the rest goes through the fabric itself. Fabrics consist of types of fibers and possess intricate surface patterns that can soak up and scatter UV rays to lessen their transmission. The ways in which UV rays scatter and reflect differ based on the unique surface shapes of individual fibers as well, as the fabric’s structure and color intensity. Henceforth‌‌ ‌when‌ ‌examining‌ ‌the‌ ‌effectiveness‌ ‌of‌ ‌textiles‌ ‌against‌ ‌harmful‌ ‌UV rays it’s crucial to take into account a range of aspects thoroughly.

Fiber type

Different types of fibers exhibit varying degrees of absorption. Diffuse reflection of ultraviolet rays due to factors such as their composition and structure at the molecular level as well as surface characteristics and cross-sectional shapes they possess. Even if made from the material fibers with different cross sections reflect ultraviolet rays differently with absorption capabilities influenced by the contact surface area. In comparison, to cross-section synthetic fabrics, flat and irregular fiber synthetic fabrics demonstrate better performance in this regard. Fabrics with fibers offer more protection against UV rays compared to fabrics with long fibers while silk products that are processed outperform raw silk products made from synthetic fibers and finer fabrics are preferable, to rougher ones.

Treatment fabric

Fabrics that have been treated with finishes like coating or water and oil repellent may see an improvement in their UV protection properties as a result of the process. This enhancement can be attributed to the increased thickness and reduced porosity of the fabric, after treatment well as the inherent UV shielding capabilities of the finishing agent itself.

2. Anti UV Finishing Mechanism and Anti UV Finishing Agents

Mechanism of UV resistant finishing

When light hits an object optically it reflects off some of the surface gets absorbed by the object in part and passes through the object for the rest. Typically speaking the sum of transmittance minus reflectance plus absorbance equals 100%. The idea, behind ultraviolet processing involves using ultraviolet shielding agents to treat fibers or fabrics. When sunlight hits the fabric surface only a small portion penetrates through the openings in the material; most of it gets reflected back or absorbed by the ultraviolet protection compound and transformed into lower energy before being emitted again. Effectively thwarting ultraviolet rays. In essence, textiles shield against radiation, through two main methods; reflecting light off and absorbing it.

UV resistant finishing agent

There are two categories of finishing agents commonly used for UV resistance, inorganic and organic options.

1. Inorganic UV resistant finishing agents:

Most of the employed inorganic UV-resistant finishers consist of metals and metal oxides along with their salts referred to as UV protective agents in the field of materials science and engineering. These inorganic substances equipped with UV protection capabilities exhibit characteristics such as being harmless to humans and animals despite lacking any odor or irritation upon contact with skin; showcasing thermal stability without decomposing or evaporating easily; and demonstrating effective shielding against harmful ultraviolet rays. They are known to serve as secure protective agents, against UV rays while also possessing the added benefits of inhibiting the proliferation of bacteria and fungi and ward off unpleasant odors.

2. Organic UV resistant finishing agents:

Organic UV resistant shielding agents are specifically classified as follows:

Benzone compounds.

Benzotriazole class.

Salicylic acid compounds.

Organic nickel polymer.

Triazine class.

Replace acrylonitrile.

Cinnamate esters

Aminobenzoic acid and its esters.

3. Production of UV resistant fibers and textiles

UV resistant fiber

Lately, in China, there has been advancement in creating anti-UV fibers with a particular focus on developing polyester materials that offer UV protection. These include types like polyester staple fiber, polyester POI, FDV, UDF, and DTU. Certain polyester fibers have been able to block as much, as 94 to 98% of UV rays.

There are methods to create fibers that resist UV rays effectively and these can be categorized into the following four types.

Post implantation method

After completing the production process of fibers like cotton fibers with UV resistance in mind through methods such, as immersion and dye baths or printing techniques to embed anti-UV finishing agents into the fibers.

Copolymerization spinning method

The copolymerization spinning method first copolymerizes ultraviolet absorbers with monomers of fiber-forming polymers and then produces polymers with anti-ultraviolet function. Then, conventional spinning methods are used to produce anti-ultraviolet fibers. This method is mainly used to produce polyester synthetic fibers with anti-ultraviolet function. These fibers have good anti-ultraviolet properties and can effectively absorb ultraviolet rays with wavelengths of 280-340nm.

Blended spinning

Blended yarn can be categorized as blended yarn and sliced blended yarns are available in the market for synthetic fiber varieties that are spun directly; one can enhance these fibers UV protection by incorporating anti UV finishing agents in either the spinning fluid (spinning melt or spinning solution) or directly, into the polymer material itself.

Composite spinning method

The fibers produced through spinning typically exhibit a skin core structure wherein the core layer is infused with UV resistant finishing agents and the outer layer is composed of traditional polymer materials.

UV resistant textiles

UV resistant textiles are created through textile finishing processes that focus on using agents to resist UV radiation and preparing liquids for finishing applications while choosing appropriate finishing methods.

Surface coating method

Applying a UV finishing agent to the coating agent and then using a coating machine to create a film on the fabric surface through drying and heat treatment is how the surface coating method achieves UV protection and sun protection functions effectively on various types of fibers at a low cost without the need, for advanced application techniques or equipment requirements. The texture and characteristics of the items treated using this technique may experience some changes in terms of their look. How well they absorb water and allow air to pass through them. This method is typically employed when working with materials, like work attire sunshades and tents.

Immersion method

(1) Dyeing in the same bath method. Polyester UV absorbers have hydrophobicity and a certain affinity for polyester, so high-temperature and high-pressure dyeing processes can be used to achieve UV resistant finishing and dyeing in the same bath.

(2) Separate immersion method. Water soluble UV absorbers, due to their sulfonic acid groups, can be used in the same bath with anionic dyes such as acid dyes and metal complex dyes for dyeing wool, silk, and nylon. This method is suitable for wool, silk, nylon, and cotton fabrics, but not very suitable for polyester fabrics due to high costs and unsatisfactory results.

Printing Law

To enhance the color durability of printed fabrics against light exposure betterment is achieved by including UV absorbers in the printing paste along with dyes often utilized for interior decorative fabrics that demand high lightfastness levels; hence foreign countries commonly opt for UV absorbers and dyes with superior light resistance for co printing purposes, on their textiles.

Immersion rolling method

The immersion rolling technique works well with types of fabrics; water soluble UV absorbers can bind to hydrophilic fibers and insoluble UV absorbers can bind to hydrophobic fibers when exposed to high temperatures, similar to the process of hot melt dyeing, with dispersed dyes.

Microcapsule processing

Creating microcapsules through microcapsule processing includes the fabrication of capsules containing ultraviolet absorbers that are enveloped by high molecular weight polymers using a technique that combines polymerization and microencapsulation simultaneously. Encapsulating absorbers, within the core of the capsule and subsequently attaching the microcapsules to fabric using adhesives and crosslinking agents yields textiles with ultraviolet protection exceeding 85%.

4. Evaluation of Fabric UV Resistance Performance

There are many standards for measuring the UV resistance of fabrics, such as AS/NZS 4399-1996 in Australia and New Zealand, GB/T 18830-2009 in China, AATCC183-2014, ASTM D6603-2012, ASTM D6544-2012 in the United States, etc.

Evaluation method for UV resistance performance

Standard testing method

The Chinese standard GB/T 18830-2009 “Evaluation of UV Protection Performance of Textiles” specifies the test methods for UV protection performance of textiles, as well as the evaluation and expression methods for protection level. This standard stipulates that when the UPF value of the sample is greater than 40 and the T (UV-A) is less than 5%, it can be called a UV resistant product.

Other testing methods

(1) Ultraviolet spectrophotometer method. Using a UV spectrophotometer as the radiation source, a certain wavelength range (280-400nm) of ultraviolet light is generated and irradiated onto the fabric. Then, an integrating sphere is used to collect the radiation flux passing through the fabric in various directions, and the UV transmittance is calculated. The smaller the UV transmittance, the better the fabric’s ability to shield UV rays.

(2) UV intensity accumulation method. Using ultraviolet (UV) light to irradiate a fabric placed on a UV intensity accumulator, irradiate it for a given time, measure the cumulative amount of UV light passing through the fabric, and then calculate it. The smaller the cumulative amount of ultraviolet radiation through the fabric, the better.

(3) Illuminometer method. Using a UV lamp as the light source and adding UV transparent glass to the illuminance meter, measure the cumulative amount of Q8 passing through the sample and the cumulative amount of irradiation without placing the sample.

(4) Fading method. Cover the sample on the light fastness standard card, 50cm away from the sample, and irradiate it with ultraviolet light to determine the time for the light fastness standard card to change color to level 1. The longer the time used, the better the shielding effect.

Indicators for evaluating UV resistance performance

UV transmittance ratio

UV transmittance is the measurement of UV radiation passing through a sample compared to UV radiation passing through without a sample present. Using transmittance helps assess the UV protection provided by fabrics and allows for calculations to determine if a fabric’s UV transmittance is below the acceptable level to prevent skin damage from UV rays, in certain situations.

UV shielding rate

The rate of UV protection is a measure that helps consumers understand how well a product blocks UV rays in a straightforward manner that resonates with them easily. Though UV transmittance and UV shielding rate may be explained differently based on varying viewpoints they essentially convey the meaning to the average person.

Sun protection factor (SP). Ultraviolet ray shielding level (URSL).

SPFs are common in cosmetics while UPFs are prevalent in textiles for UV protection purposes. The UPFs gauge the UV resistance level of fabrics. Are crucial for evaluating their performance, against UV rays.

Penetration rate

In national standards, UPF value and UV-A transmittance are used together as indicators to evaluate UV resistance performance, with UPF value greater than 30 and UV-A transmittance not exceeding 5%.

5. Exploring BEGOODTEX Anti-UV Flame–retardant Technology

BEGOODTEX offers anti-UV flame retardant fabrics for safety and durability in both commercial and residential settings. Our application in protective clothing and interior decoration materials demonstrates the versatility and effectiveness of these high-performance textiles.