Measuring the UV protection factor (UPF) of fabrics and clothing

Significance of the Topic

Ultraviolet radiation from the sun poses health risks such as erythema and skin cancer. The depletion of the ozone layer increases UVB levels reaching the surface. Protective clothing with a defined Ultraviolet Protection Factor (UPF) offers an effective defense by blocking or attenuating harmful UV wavelengths. Reliable laboratory methods for assessing UPF are essential for developing sun-protective textiles and ensuring consumer safety.

Objectives and Study Overview

This study aimed to evaluate the UPF of six textile samples with varied constructions (woven and knitted) and fiber compositions using a spectrophotometric approach. The work aligns with proposed Australian standards for sun-protective clothing and applies a diffuse reflectance accessory to improve measurement safety and accuracy compared to in vivo testing.

Methodology and Instrumentation

An integrating sphere accessory coupled with an Agilent Cary 3E UV-Vis spectrophotometer measured direct and diffuse spectral transmittance from 280 to 390 nm at 1 nm intervals. Each fabric sample was secured close to a Schott UG11 filter before the sphere entrance to eliminate fluorescence artifacts. Measurements were performed on eight sub-samples per fabric (machine and cross-machine directions). UPF calculations were carried out using the Cary UPF Easy Menu software.

Instrumentation Used

• Cary 3E UV-Vis Spectrophotometer
• Cary 1/3E Diffuse Reflectance Accessory (integrating sphere)
• Cary Fabric Holder
• Schott UG #11 filter
• UPF Easy Menu software package

Main Results and Discussion

Textile UPF values ranged from non-rateable (<5) to maximum (>50), with knitted cotton and woven wool fabrics offering the highest protection. Mean UV transmission in the UVB (290–315 nm) and UVA (315–380 nm) regions correlated with UPF ratings. Spectral transmittance curves highlighted wavelength-dependent variations, confirming the need for full-spectrum measurement. The method demonstrated reproducibility (CV <9%) and confidence limits within acceptable bounds.

Benefits and Practical Applications

This spectrophotometric procedure provides a non-invasive, rapid, and accurate assessment of fabric UV protection. It supports quality control in textile manufacturing, garment classification by protective performance, and compliance with emerging standards for sun-protective clothing.

Future Trends and Potential Applications

Advances may include automated high-throughput UPF screening, enhanced spectral models addressing UVA-induced photoaging effects, and integration with wearable UV sensors for real-time monitoring. Research into dynamic UV-blocking smart textiles and novel fabric treatments also represents promising directions.

Conclusion

The use of a diffuse reflectance accessory with dedicated software enables reliable UPF determination across the critical UV spectrum. This laboratory-based approach improves safety over human-subject testing and delivers consistent, reproducible results, facilitating better textile design and consumer protection.

References

• Gies P, Roy C. Ultraviolet radiation, ozone thinning, the environment and UPF testing. SDCANZ Textiles and Sun Protection Conference; 1993. p. 6–24.
• United Nations Environment Programme. Environmental Effects of Ozone Depletion. Nairobi; 1991.
• Welsh C, Diffey B. The protection against solar actinic radiation afforded by common clothing fabrics. Clin Exp Dermatol. 1981;6:77–82.
• CIE Research Note. A reference action spectrum for ultraviolet induced erythema in human skin. CIE J. 1987;6:17–22.
• Menzies S, Lukins P, Greenoak G, Walker PJ, Pailthorpe MT, David SK, Georgouras KE. A comparative study of fabric protection against ultraviolet-induced erythema determined by spectrophotometric and human skin measurements. J Photodermatol Photoimmunol Photomed. 1992;8(4):157–163.