UV Absorption Testing

Ultraviolet (UV) absorption testing mainly conducts scientific testing and analysis on items including the ultraviolet protection factor, UVA transmittance and protection grade, UVB transmittance and sun protection factor, UV absorption rate determination at specific wavelengths, UV blocking durability testing, and material light stability and anti-aging performance evaluation, objectively assessing the product quality grade and issuing a detailed test report, providing a basis for the production enterprise quality control and downstream user product acceptance.

Testing items

Ultraviolet protection factor (UPF) determination: The UPF value is a key indicator for evaluating the overall protection capability of products such as textiles and sunscreens against ultraviolet radiation (especially UVA and UVB). In the test, the transmission amount of ultraviolet radiation under the sample-covered and uncovered states is compared, and the UPF value is calculated; for example, UPF 50 means that only 1/50 of the ultraviolet rays can penetrate the material, which is the core basis for judging the effectiveness of sun-protective products.

UVA transmittance and protection grade (PA) evaluation: This item specially determines the blocking capability of products against long-wave ultraviolet radiation (UVA, wavelength 315-400 nm). By measuring the UVA transmittance at specific wavelengths, the PA protection grade (such as PA+, PA++ and PA+++) can be converted and evaluated. UVA has strong penetration ability and is the main factor causing skin photoaging and pigmentation; therefore, this test is of vital importance to sun-protective cosmetics and anti-aging materials.

UVB transmittance and sun protection factor (SPF) correlation test: This item mainly evaluates the shielding effect of samples against medium-wave ultraviolet radiation (UVB, wavelength 280-315 nm). UVB is the main cause of immediate sunburn and erythema of the skin. In the laboratory, the UVB transmittance spectrum is determined by the in vitro method, and the data can serve as the basis for calculating the in vitro SPF value, which is used for the rapid screening and evaluation of the sunburn protection potential of sun-protective products.

UV absorption rate determination at specific wavelengths: This test aims to precisely measure the light absorption performance of materials at specific wavelengths in the ultraviolet band (such as 370 nm UVA and 310 nm UVB). Through scanning with a UV-Vis spectrophotometer, the absorption spectrum is obtained, which can directly reflect the ultraviolet absorption characteristics of materials (such as polymer materials, UV absorbers and coatings), and is used for formulation development and quality control.

UV blocking durability testing: Evaluate the retention rate of the ultraviolet protection performance of products after simulated use environments (such as water immersion, perspiration, rubbing and light exposure). For example, test whether the UPF value of sun-protective clothing decays after multiple washes, or carry out water-resistance tests on sunscreens. This item is directly related to the actual use effectiveness and service life of products, and is an important link in evaluating their quality reliability.

Material light stability and anti-aging performance evaluation: By placing materials under strong ultraviolet radiation environments for accelerated aging tests, monitor the changes in the contents of ultraviolet absorbers, mechanical properties (such as tensile strength), color and surface morphology. This test is widely used in fields such as plastics, coatings, rubber and automotive interior materials, and is used to predict the durability of materials during long-term outdoor use.

Testing scope

Textiles and garments: Mainly include sun-protective clothing, beach wear, outdoor sportswear, hats, parasols and tents. The testing focus is the ultraviolet protection factor (UPF) of fabrics, evaluating the influences of factors such as the weaving density, fiber type, color and whether anti-ultraviolet finishing agents are used on the protection effect.

Cosmetics and personal care products: The core testing objects are sunscreens, sunscreen sprays, lip balms, foundations and day creams with sun-protective functions. The tests need to be carried out in accordance with relevant regulations (such as the Safety and Technical Standards for Cosmetics of China), determining the SPF value, PFA value (long-wave ultraviolet protection index), critical wavelength and broad-spectrum sun protection performance, to ensure that the claimed sun protection effects are true and effective.

Polymer materials and plastic products: Cover outdoor plastic building materials (such as PC sheets and PVC profiles), automotive parts, packaging films and agricultural greenhouse films. The tests mainly focus on the effectiveness of the ultraviolet absorbers and light stabilizers added to materials, and evaluate the anti-yellowing and anti-embrittlement capabilities through ultraviolet transmittance and accelerated aging tests.

Coatings and paint films: Include exterior wall architectural coatings, automotive topcoats, wood coatings and functional sun-protective coatings. The testing purpose is to evaluate the ultraviolet shielding and protection effect of coatings on substrates, as well as the changes in the gloss, color and adhesion of the coatings themselves under ultraviolet irradiation, ensuring that their decorative and protective properties are durable.

Glass and optical materials: Involve automotive windshields, architectural curtain wall glass, sunglass lenses and optical lenses. The testing focus is to measure their transmittance in the UVA and UVB bands; in particular, sunglasses need to comply with relevant standards (such as GB/T 10810.3), so as to ensure effective blocking of harmful ultraviolet rays and protect eye health.

Other functional products: The scope extends to automotive window films, outdoor advertising materials, cultural relic protection coatings, and certain UV-sensitive pharmaceutical and food packaging. The tests aim to verify the capability of these products to prevent the degradation and deterioration of contents caused by ultraviolet irradiation under specific use environments.

Testing methods

In vitro instrumental test method (spectrophotometric method): This is the most core and commonly used method. A UV-Vis spectrophotometer equipped with an integrating sphere is used to directly measure the transmittance spectrum of samples in the ultraviolet band (usually 280-400 nm). By calculating the weighted average of the transmittance, key parameters such as the UPF value and the UVA/UVB transmittances can be obtained, with the advantages of being fast, objective and highly repeatable.

In vitro sun protection factor determination method (in vitro SPF method): Based on the spectrophotometric principle, a UV light source and detector at specific wavelengths are used to simulate a human skin model (such as a polymethyl methacrylate plate or collagen film); after applying the sunscreen sample, the ultraviolet transmittance is determined, and the in vitro SPF value is calculated through a preset formula. This method is often used for the rapid screening in the product development stage.

In vivo human test method (in vivo SPF method): Recognized as the gold standard for determining the SPF value of sun-protective cosmetics. A quantitative amount of sunscreen product is applied to the non-sun-exposed skin of the backs of volunteers, and a simulated solar ultraviolet light source is used for irradiation with increasing doses; the ultraviolet dose required to produce minimal erythema is determined, and the SPF value is calculated by comparison with unprotected skin. The results of this method are closest to the actual use effect, but the cost is high and the time consumption is long.

Accelerated aging test method: The samples are placed in an artificial weathering aging chamber or a xenon lamp aging test chamber, and under the controlled temperature, humidity and water spray conditions, they receive strong ultraviolet irradiation for accelerated aging. Samples are taken periodically, and the attenuation of their ultraviolet absorption performance is evaluated by the spectrophotometric method or other physical performance tests, so as to predict the outdoor service life of products.

Chemical analysis method: Through instruments such as high-performance liquid chromatography (HPLC), quantitatively analyze the original contents of specific ultraviolet absorbers in materials (such as benzophenone-type and benzotriazole-type absorbers) and their residual amounts after photoaging. This method is direct and effective, and is often used to verify the formulation contents and study the migration and loss mechanisms of absorbers.

Standard lining method (for textiles): In accordance with standards (such as GB/T 18830 and AS/NZS 4399), the textile specimen is closely covered on a UV sensor or a standard UV transmittance plate, and under a specified UV light source, the ultraviolet radiation intensities with and without the specimen are respectively measured; the UPF value and the UVA and UVB transmittances are calculated.

Testing standards

Domestic standards:

1. GB/T 18830, Textiles - Evaluation of ultraviolet protection performance

2. GB/T 10810.3-2025, Uncut finished spectacle lenses - Part 3: Transmittance test methods

3. Safety and Technical Standards for Cosmetics (China)

4. GB/T 6682-2008, Water for analytical laboratory use - Specification and test methods

5. GB/T 602, Chemical reagent - Preparations of standard solutions for impurity determination

6. GB/T 603, Chemical reagent - Preparations of reagent solutions for use in test methods

International standards:

1. AS/NZS 4399:2017, Sun protective clothing - Evaluation and classification

2. ISO 24444:2019, Cosmetics - Sun protection test methods - In vivo determination of the sun protection factor (SPF)

3. ISO 3696, Water for analytical laboratory use - Specification and test methods

Note: The applicable standard can be selected according to the product use and customer trade requirements; standards agreed in the contract take precedence over general standards.

Testing Instruments and Equipment

UV-Vis spectrophotometer (with integrating sphere): This is the core equipment for ultraviolet absorption testing. The integrating sphere is used to collect all the light scattered and transmitted by the sample, ensuring the accuracy of the measurement results. The equipment needs to have a wavelength scanning function covering the ultraviolet band of 290-400 nm, and can automatically calculate parameters such as the UPF value and transmittance; it is the standard configuration of laboratories.

Ultraviolet radiation sources and sun protection factor determination instruments: Specially used for the SPF value testing of sun-protective products. They include xenon lamps or multi-port UV light sources simulating the solar spectrum, monochromator or filter systems, and highly sensitive ultraviolet radiation detectors. The in vivo testing instruments also need to be equipped with precise dose control systems and erythema observation equipment.

Artificial weathering aging test chambers: Mainly used for the durability testing of materials. The common types are xenon arc lamp aging chambers and ultraviolet fluorescent lamp aging chambers (such as UVA-340 and UVB-313 lamps). They can simulate and strengthen the ultraviolet radiation in sunlight, and controllably superimpose environmental factors such as temperature, humidity and rain spray, so as to realize accelerated aging.

Standard UV transmittance testing instruments: Portable or desktop instruments specially designed for textiles, films and other materials. They usually have built-in UV light sources and detectors at specific spectral lines, can directly and quickly read the UPF value and the ultraviolet transmittance, and are simple to operate; they are often used for the online quality control of factories and the market supervision sampling inspections.

High-performance liquid chromatograph (HPLC): Used for the qualitative and quantitative analysis of organic ultraviolet absorbers in materials. By being combined with UV detectors or mass spectrometry detectors, it can precisely determine the contents of specific UV absorbers in various complex formulations, as well as their stability changes during product storage or use.

Sample preparation and processing equipment: Include precise sample cutters, coating preparation devices (such as wire bar coaters), constant temperature and humidity chambers, and standard washing and rubbing testing machines. These auxiliary equipment ensure the standardization and consistency of the test sample preparation, and are the basis for obtaining reliable and comparable test results.