Shedding Some Light on Textile UV Testing

How do you know if UV test results from one vendor to the next give you an accurate comparison? How do you know what the test results mean regarding actual world UV performance? UV testing can be a very confusing area of product formulation and product evaluation. The complexity starts with several different testing processes that can be used to evaluate ultraviolet light exposure.

UV textile testing refers to evaluating and measuring the ultraviolet (UV) protection provided by textiles or fabrics. It is essential to assess the UV protection level of materials, as exposure to harmful UV radiation can cause various health issues, including sunburn, skin aging, and an increased risk of skin cancer.

UV textile testing involves subjecting the fabric to specific laboratory tests to determine its UV protection factor (UPF) or ultraviolet protection factor (UPF). The UPF indicates the fabric's ability to block or absorb UV radiation and prevent it from reaching the skin.

Here are some standard methods used for UV textile testing:

• Spectrophotometric analysis: This method involves using a spectrophotometer to measure the transmission of UV radiation through the fabric. The fabric sample is exposed to UV radiation and the amount of transmitted and absorbed UV radiation is measured. The UPF is calculated based on the ratio of the radiation transmitted through the fabric to the radiation transmitted through a reference material.
• Standardized testing protocols: Various international standards and guidelines exist for UV textile testing. For example, the American Association of Textile Chemists and Colorists (AATCC) and the International Organization for Standardization (ISO) have established specific test methods and requirements for determining UPF values.
• Aging tests: Fabrics may undergo accelerated aging tests to assess the durability and longevity of their UV protection. These tests simulate long-term exposure to sunlight and evaluate how the fabric's UV protection performance changes over time.
• Certification and labeling: Once a fabric has been tested and assigned a UPF, it may be eligible for certification or labeling. Specific organizations or programs provide certification or labeling to textiles that meet specific UV protection criteria. These labels inform consumers about the fabric's UV protection level and help them make informed choices.

Some specific types of accelerated weathering testing are:

• QUV (A & B)
• Xenon Arc
• Accelerated Outdoor Exposure
• Actual Outdoor Exposure

Within these different testing methods, other variations can impact the results.

In each case, the hours of exposure is the measure that is used to determine fading, plastisol migration, and reduction of core fabric strength. Several specimens are put into the testing device simultaneously, with a control sample set aside for comparison purposes. Examples are taken from the testing equipment at measured intervals and compared to the control. At the end of the testing process, 4 to 10 specimens would be compared to the power to see the degradation caused by exposure to the test method over some time. Pretty simple. Wrong.

Different testing devices require different levels of exposure because of the light source.

Exposure Time

Each test method requires different levels of exposure to represent a period in a natural world environment. As a rule, the following hours of exposure represent one year in a Florida-like environment, assuming the testing equipment has a moisture cycle to simulate humidity.

Each light source has a unique impact on the fabric specimen.  Generally speaking, Xenon Arc is a better testing method for color fading, but QUV is better for strength evaluations.

Proper exposure to "real world" exposure is not the same as lab testing because actual fabric degradation is influenced in varying degrees by three factors:

• Light
• Humidity
• Temperature

Even under the best circumstances, a lab cannot accurately replicate these factors to give you exact "real world" performance. Every climate and every year of exposure are different when testing material outdoors.

Now back to the real world that we live in:

We need more than one testing apparatus, and several, to determine the expected UV life of your products. How do you make the best decision on fabric choice related to UV? Different manufacturers can provide UV results using the same test method or have a lab test compare products simultaneously using the same testing devices and procedures.

At a minimum, you should ask a manufacturer for their UV resistance test results, understand their test method, and use the table above to compare the performance.  

Finally, the best UV resistance indicator is experience. Because of the nature of different climates, the best way to be sure that the suitable fabric will work for you in your application is proven performance.  Has the material worked successfully in the past? Does the manufacturer have a track record of proven performance with the outdoor color fastness and product strength? All of the test methods we have discussed will help you understand the different techniques, but real-world exposure is the best answer to the question of future UV performance.