Yellow Resistance Testing Service

Yellow Resistance Testing Service – Comprehensive Evaluation of Colour Stability and Anti‑Yellowing Performance for Materials, Coatings and Finished Products

As an ISO/IEC 17025 accredited independent testing laboratory, we offer specialised yellow resistance testing services to manufacturers, quality assurance teams, and regulatory bodies across the plastics, coatings, textiles, footwear, automotive, construction, and consumer goods sectors. Yellowing – the gradual development of a yellowish discolouration on the surface or throughout the bulk of a material – is a common and often irreversible degradation phenomenon caused by exposure to ultraviolet (UV) light, heat, oxygen, chemical agents, or the combination of these environmental factors. This aesthetic and functional defect can significantly reduce the perceived quality, market value, and service life of products ranging from white or light‑coloured plastics and paints to transparent films, adhesives, and textiles. Our yellow resistance test protocols simulate the most common yellowing mechanisms – including UV‑induced photo‑oxidation, thermal oxidation, and chemical stain yellowing – to quantify the colour change and to predict the long‑term colour stability of your materials. All methods are aligned with ISO, ASTM, EN, and GB standards, including ISO 105‑B02 (Colour fastness to artificial light), ASTM D1925 (Standard Test Method for Yellowness Index of Plastics), ASTM E313 (Standard Practice for Calculating Yellowness and Whiteness Indices), ISO 4892‑3 (Plastics – Exposure to laboratory light sources), ASTM D1148 (Standard Test Method for Rubber Deterioration – Discoloration from UV and Heat), and GB/T 2409 (Plastics – Determination of yellowness index). Our inspection and test reports are recognised by the National Medical Products Administration (NMPA), the State Administration for Market Regulation (SAMR), the Ministry of Industry and Information Technology (MIIT), and international certification bodies for product registration, type approval, and quality assurance.

Materials and Products We Regularly Test

Our yellow resistance testing facilities accommodate a wide range of material types and finished products. Typical test articles include:

• Plastics and polymer materials – thermoplastics (ABS, PC, PA, PP, PE, PS, PVC), thermosets (epoxy, phenolic, polyurethane), and engineering plastics for automotive, electronics, and construction applications
• Coatings, paints and varnishes – architectural coatings, automotive clearcoats, industrial finishes, powder coatings, and wood coatings
• Textiles and leather – apparel fabrics, upholstery, automotive interior textiles, synthetic leather, and natural leather
• Elastomers and rubbers – natural rubber, synthetic rubber (SBR, NBR, EPDM), silicone rubber, and polyurethane elastomers
• Adhesives and sealants – structural adhesives, sealants, and pressure‑sensitive adhesives (PSAs)
• Packaging materials – transparent films, labels, flexible packaging, and rigid containers
• Footwear and shoe materials – outsoles, midsoles, upper materials, and adhesives
• Paper and paperboard – packaging papers, printing papers, and decorative papers
• Transparent and translucent materials – glass, optical plastics, and transparent films

Yellowing Mechanisms – Understanding the Causes of Discolouration

• UV‑induced yellowing (photo‑oxidation) – the most common mechanism – Exposure to ultraviolet (UV) radiation (especially UVA and UVB) from sunlight or artificial light sources causes the formation of chromophores (colour‑producing groups) in the polymer matrix. This occurs through photo‑oxidation of the polymer chains, which leads to the formation of carbonyl groups, conjugated double bonds, and other light‑absorbing structures. UV‑induced yellowing is the primary cause of colour change in outdoor and indoor applications (e.g., automotive interiors, building facades, and outdoor furniture).
• Thermal yellowing (heat‑induced oxidation) – due to high‑temperature exposure – Exposure to high temperatures (typically > 80 °C) accelerates the oxidation of polymers and other organic materials, leading to the formation of chromophores. Thermal yellowing is common in applications involving high‑temperature processing (e.g., injection moulding, extrusion), as well as in high‑temperature service environments (e.g., engine compartments, cookware).
• Chemical yellowing – due to contact with reactive chemicals – Contact with certain chemicals (e.g., nitrogen oxides (NOx), ozone, phenols, amines, or acid gases) can cause chemical reactions that lead to yellowing. This is common in packaging (where the package contents or the printing inks can cause yellowing), in textiles (where perspiration or bleaching agents can cause yellowing), and in coatings (where exposure to industrial atmospheres can cause yellowing).
• Synergistic yellowing – the combined effect of UV, heat, moisture and chemicals – In many real‑world service environments, materials are exposed to a combination of UV radiation, heat, moisture, and chemical agents. The combined effect can be more severe than the sum of the individual effects, leading to accelerated yellowing and degradation.

Yellow Resistance Test Methods – Simulating Environmental Exposure

• Accelerated UV ageing (xenon‑arc and UV fluorescent) – ISO 105‑B02 / ISO 4892‑3 / ASTM G154 / ASTM G155 – We use xenon‑arc chambers (which simulate full‑spectrum sunlight) and UV fluorescent chambers (UVA‑340 and UVB‑313 lamps, which emit high‑intensity UV radiation) to accelerate the yellowing process. The specimens are exposed to a controlled cycle of UV exposure, condensation, and temperature (typically 50‑75 °C) for a specified number of hours (e.g., 100, 250, 500, 1 000, 2 000 hours). The test parameters are selected to match the specific service environment (outdoor, indoor, or accelerated).
• Thermal ageing (oven ageing) – ASTM D1148 / ISO 188 – for heat‑induced yellowing – We place the test specimens in a temperature‑controlled oven (or an environmental chamber) at a specified temperature (e.g., 70 °C, 100 °C, 125 °C) for a specified period (e.g., 24, 48, 72, 168 hours, or up to 1 000 hours). The specimens are then removed and cooled, and the colour change is measured. The test is used to simulate the yellowing caused by high‑temperature processing (e.g., injection moulding, extrusion) and by high‑temperature service conditions.
• Heat‑UV combined ageing – for simulating outdoor and accelerated outdoor conditions – We combine UV exposure (using a xenon‑arc or UV fluorescent chamber) with thermal ageing (by heating the chamber to a specified temperature) to simulate the combined effect of sunlight and heat. The test is performed under a controlled humidity level (typically 50‑95 % RH) to simulate the effect of moisture.
• Chemical yellowing resistance – ISO 105‑X12 / ASTM D2244 / GB/T 3920 – for assessing resistance to staining agents – We apply a specified chemical agent (e.g., a staining agent, a bleach solution, or a perspiration solution) to the specimen and assess the yellowing after a specified exposure time (typically 24‑72 hours). The test is used to evaluate the resistance of textiles, leather, and packaging materials to yellowing caused by contact with chemicals.
• Real‑time yellowing test – for natural outdoor exposure – ASTM G7 / ISO 877 – For the most realistic assessment, we offer natural outdoor yellowing tests by exposing the specimens to sunlight (at a specified exposure angle, typically 45° south‑facing) for 3, 6, 12, or 24 months. The specimens are inspected and measured periodically for yellowing.

Yellowing Measurement – Quantifying Colour Change and Yellowing Intensity

• Yellowness index (YI) – ASTM D1925 / ASTM E313 / GB/T 2409 – the primary parameter for yellowing assessment – The yellowness index (YI) is a single number that describes the degree of yellowing of a material. It is calculated from the tristimulus values (X, Y, Z) measured using a spectrophotometer (with a D65 illuminant and a 10° observer). The YI is defined as: YI = (100 × (Cx × X – Cz × Z)) / Y, where Cx and Cz are constants (Cx = 1.301, Cz = 1.149 for ASTM D1925). A higher YI indicates a greater degree of yellowing. We report the YI of the specimen before and after exposure, and the ΔYI (the change in yellowness index) is calculated. A ΔYI of ≤ 2.0 is generally considered acceptable for most aesthetic applications; for premium applications, a ΔYI of ≤ 1.0 may be required.
• Colour coordinates and colour difference (ΔE*) – CIELAB (L*, a*, b*) – ISO 11664 / ASTM D2244 – We measure the colour coordinates (L*, a*, b*) before and after exposure using a calibrated spectrophotometer. The colour difference (ΔE*) is calculated using the CIELAB colour difference formula (or the CIE94, CMC, or CIEDE2000 formula, as specified). The ΔE* value is used to assess the overall colour change, and it is compared to the specified acceptance criterion (e.g., ΔE* ≤ 2.0).
• Whiteness index (WI) – ASTM E313 / ISO 11476 – for assessing the loss of whiteness – For white materials, we measure the whiteness index (WI) before and after exposure. The loss of whiteness (ΔWI) is calculated and used as an indicator of yellowing. A ΔWI of ≥ 2.0 is considered a significant loss of whiteness.
• Visual assessment and grey scale rating – ISO 105‑A02 / ASTM D1729 / GB/T 250 – We perform a visual assessment of the colour change using the ISO grey scale (1‑5, where 5 = no change, 1 = severe change) under controlled viewing conditions (D65 illuminant, 10° observer). The grey scale rating is used as a quick and practical measure of the yellowing severity.
• Surface gloss change – ISO 2813 / ASTM D523 – for assessing the loss of gloss due to yellowing – For coated surfaces, we measure the 60° gloss before and after exposure. A significant reduction in gloss (e.g., > 20 %) often accompanies yellowing and is reported as an additional indicator of surface degradation.

Material‑Specific Yellowing Mechanisms – Plastics, Coatings, Textiles and Elastomers

• Yellowing of plastics – due to photo‑oxidation and thermal oxidation – For plastics (especially white and light‑coloured plastics), yellowing is caused by the formation of conjugated double bonds and carbonyl groups in the polymer backbone. We test plastics for yellow resistance under UV and thermal exposure, and we provide the ΔYI and ΔE* values for the material.
• Yellowing of coatings and paints – due to degradation of the binder and the pigment – For coatings and paints, yellowing can be caused by the degradation of the resin binder (e.g., alkyd, epoxy, polyurethane) or by the breakdown of the pigments. We test coatings using UV, thermal, and chemical exposure, and we evaluate the yellowing, gloss loss, and chalking.
• Yellowing of textiles and leather – due to photo‑oxidation and chemical staining – For textiles and leather, yellowing can be caused by UV exposure (photo‑oxidation of the fibres), by exposure to atmospheric pollutants (NOx), or by contact with staining agents. We test textiles and leather for yellowing using UV exposure, thermal ageing, and chemical staining tests.
• Yellowing of elastomers and rubbers – due to photo‑oxidation and ozone attack – For elastomers and rubbers, yellowing is often caused by the photo‑oxidation of the polymer and the degradation of the anti‑oxidants and anti‑ozonants. We test elastomers using UV exposure, ozone exposure, and thermal ageing.

Regulatory Compliance and Product Certification – Supporting Industry Standards

Our yellow resistance testing services are performed in accordance with a wide range of national and international standards. The most commonly requested include:

• ASTM D1925 – Standard Test Method for Yellowness Index of Plastics – the primary standard for measuring the yellowness index of plastics
• ASTM E313 – Standard Practice for Calculating Yellowness and Whiteness Indices from Instrumentally Measured Colour Coordinates – for calculating the yellowness and whiteness indices
• ISO 105‑B02 – Colour fastness to artificial light – for colour fastness to xenon‑arc light
• ISO 4892‑3 – Plastics – Exposure to laboratory light sources – Part 3: Fluorescent UV lamps – for accelerated UV exposure
• ASTM G154 – Standard Practice for Operating Fluorescent Ultraviolet (UV) Lamp Apparatus for Exposure of Nonmetallic Materials – for UV exposure
• ASTM D1148 – Standard Test Method for Rubber Deterioration – Discoloration from Ultraviolet (UV) and Heat Exposure – for elastomers
• GB/T 2409 – Plastics – Determination of yellowness index – the Chinese national standard for yellowness index
• ISO 11476 – Paper and board – Determination of whiteness – CIE whiteness index – for paper and board

Report Acceptance and Regulatory Recognition

All yellow resistance tests are conducted under our ISO/IEC 17025 accreditation, using calibrated spectrophotometers, colourimeters, weathering chambers, and environmental chambers, all traceable to national and international reference standards. Our final test reports include: a complete description of the test article (material, dimensions, manufacturer), the test method and conditions (exposure type, temperature, duration, intensity), the measured parameters (yellowness index YI, ΔYI, colour coordinates L*a*b*, ΔE*, whiteness index WI, ΔWI, grey scale rating), the statistical summary (mean, standard deviation, coefficient of variation), and a clear pass/fail verdict against your specified acceptance criteria. These reports are accepted by the National Medical Products Administration (NMPA), the State Administration for Market Regulation (SAMR), the Ministry of Industry and Information Technology (MIIT), and international certification bodies for product registration, type approval, and quality assurance. Bilingual (Chinese/English) versions are available to facilitate submissions to domestic and international authorities and to support your global market access.