UV Stabilizers
Chemical safety testing.
UV stabilizers are used to protect textiles and plastics intended for outdoor applications from the effects of UV radiation from sunlight. They can also be useful in curtains behind glass or in textiles used for car interiors. Until recently, due to the cost of UV stabilizers and their added value to the final product, manufacturers and customers were primarily interested in the concentration present.
UVA and REACH / POPs
Several UV stabilizers are added to the REACH SVHC (Substances of Very High Concern) list.
These are benzotriazole-type UV stabilizers, also known as UVA stabilizers, as they function through UV absorption.
| Substance | CAS number |
|---|---|
| 2-benzotriazol-2-yl-4,6-di-tert-butylphenol (UV-320) | 3846-71-7 |
| Bumetrizole (UV-326) | 3896-11-5 |
| 2,4-di-tert-butyl-6-(5-chlorobenzotriazol-2-yl)phenol (UV-327) | 3864-99-1 |
| 2-(2H-benzotriazol-2-yl)-4,6-ditertpentylphenol (UV-328) | 25973-55-1 |
| 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol (UV-329) | 3147-75-9 |
| 2-(2H-benzotriazol-2-yl)-4-(tert-butyl)-6-(sec-butyl)phenol (UV-350) | 36437-37-3 |
POPs Regulation Limits use of UV-328
To strengthen the application and enforcement within the Union of Article 3(1) of Regulation (EU) 2019/1021, a limit value should be set for UV-328 occurring as an unintentional trace contamination in substances, mixtures or articles.
To enable laboratories to improve the accuracy of the relevant analytical methods and to ensure their uniform and adequate application, the limit value for unintentional trace contamination should be set at 100 mg/kg upon entry into force of this Regulation, at 10 mg/kg two years after its entry into force, and at 1 mg/kg four years after its entry into force.
- 05/05/25: 100 mg/kg in substances, mixtures and articles
- 05/05/27: 10 mg/kg in substances, mixtures and articles
- 05/05/29: 1 mg/kg in substances, mixtures and articles
Screening and Quantification by Centexbel
Centexbel screens for the presence of these substances using an LC-MS method. A general extract is prepared to determine whether these UV stabilizers are present in significant amounts. Additionally, the presence of other SVHC substances is checked, such as:
- Nonylphenols and nonylphenol ethoxylates
- PFOA
- Azodicarbonamide (chemical blowing agent)
- Several direct dyes
For each of these substances, a quantitative method is also available.
For benzotriazole UV stabilizers, a quantitative solvent extraction is followed by HPLC analysis. Due to the UV activity of these substances, a UV or DAD detector can be used. However, Centexbel uses MS detection for its enhanced information output (e.g., in case of overlapping peaks).
Other commonly used UVA stabilizers of this type include Tinuvin P (drometrizole) and Tinuvin 326. In addition to benzotriazoles, benzophenones are also classified as UV-absorbing stabilizers.
HALS (Hindered Amine Light Stabilizers)
Besides benzotriazoles, HALS compounds form another important class of UV stabilizers. Traditionally, nitrogen determination was used for detection, but this method lacks specificity. Thanks to the availability of triple quadrupole MS detectors, LC-MS analysis is now also possible for HALS types. Centexbel is currently developing methods to determine a range of HALS stabilizers. Since many HALS types are polymeric stabilizers, chromatographic analysis is more complex.
Hindered Phenol Stabilizers
Another group of stabilizers are antioxidants. For example, in polyolefins, hindered phenol structures are often used to prevent thermal degradation of the polymer during extrusion. This group includes BHT (butylated hydroxy toluene), which is often responsible for yellowing in clothing and can be a significant parameter in VOC emissions.
The structure and mass spectrum of BHT show that the –OH group of phenol is shielded by tertiary butyl groups.
Centexbel has an HPLC method for analyzing this group of antioxidants. In addition to BHT, the following are also determined:
- Irgafos 168
- Irganox 1010
- Irganox 1076
- Irganox 3114
- The anti-slip agent Erucamide