CHNSpec UPF-660 Testing Method: Benchmarking Fabric Ultraviolet Protection Factor (UPF) Standards to Empower Professional Testing Procedures

1. Method Application Scope
 

This testing method is used to accurately evaluate the ability of ultraviolet radiation-resistant textiles to block and transmit UV radiation. It benchmarks the fabric ultraviolet protection factor (UPF) testing standards — AATCC 183, AS/NZS 4399, and ISO 13758 — providing a reliable basis for the quantitative assessment of textile UV protection performance.
 

This method is designed to match the performance characteristics of the CHNSpec UPF-660 Analyzer, capable of testing textile samples under both dry and wet conditions, meeting the testing requirements for UV protection performance in various usage scenarios.
 

2. Standard Testing Principle
 

Using the high-precision spectrophotometric detection system built into the CHNSpec UPF-660 Ultraviolet Protection Analyzer, the transmission of ultraviolet radiation (UV-R, wavelength range 280–400 nm) through the textile sample is measured.
 

The analyzer accurately captures the transmission data of different UV wavelengths, providing the foundation for subsequent calculations. The calculation of the ultraviolet protection factor (UPF) is based on comparing the average UV-R radiation effect passing through air with the average UV-R radiation effect passing through the sample. The ratio of these two values gives the sample’s UPF value. At the same time, the analyzer can simultaneously test and calculate the percentage blocking rate of UV-A (315–400 nm) and UV-B (280–315 nm) radiation, providing a comprehensive reflection of the sample’s UV protection performance.
 

3. Testing Instruments
 

Core Instrument: CHNSpec UPF-660 Ultraviolet Protection Analyzer. The instrument integrates an advanced optical system and data processing module, featuring high stability and accuracy, enabling rapid and precise testing of textile UV protection performance.
 

Auxiliary Optical Filter: Schott Class UG11 filter, used to optimize the UV detection light path and ensure wavelength accuracy, improving test data reliability.
 

Materials for Wet-State Testing: Clean plastic food wrap: used to protect the instrument’s observation port during wet-state testing, preventing moisture ingress that could affect performance while maintaining a stable testing environment. AATCC absorbent paper: used to adjust the moisture content of wet samples, ensuring consistency of testing conditions.
 

4. Instrument Calibration
 

4.1 Overall Calibration
 

Strictly follow the operating instructions provided by CHNSpec for the UPF-660 Analyzer to perform comprehensive calibration. To ensure the accuracy of spectral transmittance measurements, it is recommended to verify the instrument using physical standard samples certified by an authoritative organization. When testing wet samples, cover the instrument’s observation port with plastic film and recalibrate to eliminate any interference the film might introduce to the test results.
 

4.2 Transmission Ratio Calibration
 

When no sample is placed in the optical path, set the instrument’s transmittance ratio to 100% as the reference relative to air. Then completely block the optical path using an opaque material and set the transmittance ratio to 0%. To verify linearity, use neutral filters or calibration mesh plates provided by CHNSpec or accredited laboratories to ensure that the instrument’s transmittance linearity across the full wavelength range meets testing requirements.
 

5. Sample Preparation
 

5.1 Sample Quantity and Dimensions
 

From each fabric to be tested, cut at least two samples, used respectively for dry-state and wet-state testing. Each sample must be at least 50 mm × 50 mm, or a circular sample with a 50 mm diameter, ensuring full coverage of the testing area. Avoid twisting, stretching, or damaging samples during cutting and handling to preserve original structure and UV protection properties.
 

If the fabric contains different colors or weave structures, prepare separate samples for each color and structure type. Each sample must be large enough to fully cover the testing aperture to accurately reflect UV protection performance across various regions.

5.2 Special Sample Handling
 

For samples exhibiting fluorescent characteristics, since fluorescent dyes or optical brighteners in the fabric may interfere with spectral transmission measurements and cause inflated readings, the test report must clearly indicate that the sample contains fluorescence and note any potential bias in results for reference during data interpretation.
 

6. Sample Conditioning
 

For dry-state testing, precondition samples according to ASTM D1776. Place each dry-state test sample in a standard atmosphere with a temperature of 21 °C ± 1 °C and relative humidity of 65% ± 2% for at least 4 hours. During conditioning, place each sample individually on a perforated rack or dedicated frame to ensure full exposure to the atmosphere and stable moisture equilibrium.
 

7. Testing Method
 

7.1 Dry-State Testing
 

Place the conditioned dry sample flat on the sample transmission port of the CHNSpec UPF-660 integrating sphere, ensuring full contact without wrinkles or air bubbles.
 

First, conduct the initial test in any orientation and record data. Then rotate the sample 45° about its center axis for a second test, recording data again. Finally, rotate another 45° (total 90° from initial) and perform the third test, recording the results.
 

If multiple color regions exist, conduct a preliminary scan to locate the area with the highest UV transmittance, then perform three tests as above in that region to obtain the sample’s worst-case UV protection performance.
 

7.2 Wet-State Testing
 

Completely immerse the test sample in distilled water for 30 minutes, gently squeezing intermittently to ensure uniform moisture absorption.
 

After soaking, remove the sample and place it between two sheets of AATCC absorbent paper, then use a padder or similar pressure device to press it, adjusting the pressure so that the sample’s moisture content is 150% ± 5%.
 

Before testing, cover the UPF-660 analyzer’s observation port with clean plastic film to prevent moisture from entering the instrument. Then, place the conditioned wet sample flat on the integrating sphere’s sample port and conduct three tests following the same rotation procedure as the dry test, recording all results.
 

8. Calculations
 

8.1 Average Spectral Transmittance
 

Using the three spectral transmittance measurements of each sample obtained by the CHNSpec UPF-660 Analyzer, calculate the average spectral transmittance as the basis for subsequent computations.
 

8.2 Ultraviolet Protection Factor (UPF) Calculation
 

The UPF of each sample is calculated using the following formula:

(Formula placeholder as in the original document)

8.3 Average UV-A Transmittance Calculation

8.4 Average UV-B Transmittance Calculation

8.5 UV-A and UV-B Blocking Rate Calculation

9. Reporting
 

After testing, generate a detailed test report including at least the following information:
 

• Basic sample information (sample name, specification, manufacturer, batch number, etc.);
• Instrument model used (CHNSpec UPF-660 Ultraviolet Protection Analyzer) and calibration details;
• Sample’s UPF value;
• Sample’s UV-A transmittance;
• Sample’s UV-B transmittance;
• Sample’s UV-A blocking rate;
• Sample’s UV-B blocking rate;
• For wet samples with actual moisture content exceeding 150%, the exact value must be clearly stated in the report.