FAQ on Light Stabilizers and UV Absorbers

FAQ on Light Stabilizers and UV Absorbers

FAQ Overview

As a professional additive supplier with over three decades of expertise in polymer anti-ageing, Beijing Tiangang Auxiliary Co., Ltd. is committed to providing customers with end-to-end support from product selection to technical implementation. This page compiles the high-frequency questions raised by procurement staff and technical engineers regarding light stabilizers and UV absorbers, as well as their application and business cooperation, helping you quickly find the information you need.

I. Basic FAQ

Q1: What is the difference between a light stabilizer and a UV absorber?

A: They cover different stages. A UV absorber takes in 280–400 nm radiation and dissipates it as heat, acting as a filter layer at the surface. A light stabilizer (HALS) traps the radicals formed during photo-oxidation and regenerates in the process. Formulations usually combine the two: the absorber blocks incoming light, the HALS scavenges radicals already formed. Either one alone rarely covers a long outdoor service life.

Q2: What do the numbers in grade names (944, 770, 622, 2020) mean?

A: Most of them follow long-standing industry codes and indicate neither molecular weight nor content. 944 and 622 are generic codes for polymeric HALS, 770 is a monomeric sebacate type, and 2020 refers to a triazine-based polymeric structure. Note that molecular-weight distribution, purity and residual monomer differ between suppliers for the same code, so matching numbers is not a basis for drop-in substitution at equal loading.

Q3: Why does the same HALS work well in PE but poorly in PVC?

A: Acidity, mainly. PVC contains chlorine and releases hydrogen chloride during processing and ageing, so the system turns acidic. The secondary-amine centre of a conventional HALS is protonated and loses its radical-scavenging ability — the familiar deactivation. Such systems call for a low-basicity grade or a NOR-structured acid-resistant product. Melt temperature and residence time also affect how the additive distributes in the matrix.

Q4: What loading is typical, and what happens if it is too high?

A: By part form: 0.1–0.5% for film and tape, 0.3–1.0% for moulded and thick-wall parts, 0.3–0.8% for fibre (as HALS); UV absorbers typically 0.2–0.5%; masterbatches are let down at 2–5% depending on active content. Beyond the compatibility limit the additive blooms to the surface — wasted material, worse appearance and print adhesion, and no linear gain in protection. The actual figure comes from a loading ladder on the real formulation.

Q5: Masterbatch or powder — how to choose?

A: A masterbatch gives uniform dispersion, no dust and accurate weighing; it suits thin parts and lines running many grades in small batches. Powder is cheaper and more flexible for large single-grade runs. With masterbatches, confirm the carrier matches the matrix — PE carrier in PE, PET carrier in PET. A carrier mismatch causes poor dispersion, interfacial defects or haze, and it is the most common mistake with masterbatches.

Q6: How does sampling and technical support work?

A: Selection usually starts from three inputs: the base resin, the wall thickness and design life, and the acidity or basicity of the other additives in the system. Our application team works from those three to propose a grade and a loading, then verifies dispersion and surface appearance on a small batch before any volume discussion. Timing depends on the project and is confirmed with sales rather than quoted as a standard figure.

Q7: Can it be used in food-contact or medical applications?

A: The precondition is that the grade appears on the relevant regulatory positive list (for example food-contact material lists) and that migration stays within the limits. Tiangang supplies compliance documents per grade. Whether a given grade fits a specific use depends on the contact conditions of the finished article — temperature, time, contacting medium — and on the regulations of the destination country. It cannot be inferred from the fact that a similar product has been used elsewhere.

Q8: What documents are needed for export?

A: SDS and a batch COA ship with the goods as standard. Compliance status under REACH, TSCA and other regional schemes is confirmed grade by grade, and some products require registration or pre-registration first. Tell sales the destination country and end use before shipment so the regulatory status of the specific grade can be checked rather than covered by a general statement.

II. Technical FAQ

Q9: How to scientifically evaluate the weathering performance of polymer materials?

A: Weathering evaluation of materials typically adopts a dual-track validation system of "laboratory accelerated ageing + outdoor natural exposure." For laboratory accelerated ageing, QUV testers simulate UV irradiation with condensation cycles, suitable for rapid screening; xenon-arc testers simulate full-spectrum solar radiation with controlled temperature and humidity, closer to real outdoor conditions. For outdoor natural exposure, Tiangang operates a "Polymer Anti-Ageing Technology R&D Center" in Beijing and an outdoor natural-exposure test site in Guangzhou. Evaluation metrics include: colour difference ΔE (characterising colour change), tensile-strength retention (characterising mechanical-property decay), and surface chalking/crazing grade (characterising appearance degradation). Tiangang's "China Plastics Weathering Technology Laboratory" can provide customers with a complete weathering technical evaluation report.

Q10: What is the difference between QUV and xenon-arc testing, and how to choose?

A: The difference between the two tests is mainly reflected in spectral distribution and application scenarios. QUV testing uses fluorescent UV lamps (UVA-340 or UVB-313), with spectra concentrated in the 280–400 nm UV band, suitable for rapid screening of light-stabilizer performance. Xenon-arc testing uses a xenon-arc lamp to simulate full-spectrum solar radiation, combined with a spray system to simulate rain erosion, better suited to simulating the combined effects of real outdoor environments. Tiangang recommends: at the early product-development stage, QUV can be used for rapid screening; at the formula finalisation stage, xenon-arc testing should be used for verification; at the final validation stage, outdoor-exposure data should be combined for comprehensive judgement. Tiangang's laboratory is equipped with complete QUV and xenon-arc facilities and can assist customers in developing test plans.

Q11: What is the principle of the synergistic use of light stabilizers and antioxidants?

A: The synergy between light stabilizers and antioxidants is based on staged interception of oxidative degradation. Polymer ageing is a free-radical chain reaction: thermal processing or UV irradiation generates initial free radicals, which then form hydroperoxides, accelerating ageing in a cycle. Antioxidants capture free radicals and decompose hydroperoxides during thermal processing, suppressing thermal oxidation. Light stabilizers (HALS) continuously capture free radicals during the light-exposure stage, and their regenerative mechanism gives them long-term effectiveness. The synergy of the two achieves full-lifecycle protection of "no degradation during processing, ageing resistance in service." Tiangang's synergistic blended products (e.g. HS-962/783, T-70/78/81) pre-mix the two types of additives in optimal ratios.

Q12: Why do hindered-amine light stabilizers (HALS) fail in acidic environments, and how to solve it?

A: The active centre of conventional HALS (e.g. HS-944, HS-770) is a secondary-amine structure, which is easily protonated in acidic environments (e.g. sulfur-containing pesticides, halogenated flame retardants, acidic fillers), losing its ability to capture free radicals and causing "deactivation." There are mainly three solutions: (1) Use low-basicity or acid-resistant HALS — such as Tiangang® HS-625 (low-basicity polymeric HALS), HS-765, HS-112 (NOR-structured liquid acid-resistant HALS). (2) Use blended acid-resistant products — such as Tiangang® T-68 (blended light stabilizer dedicated to acid-resistant environments), T-66/T-69 (agricultural-film-specific pesticide-resistant light-stabilizer additive packages). (3) Process isolation — in formula design, avoid direct contact between HALS and acidic components, or adopt a masterbatch pre-dispersion process. Tiangang's technical team can provide customised solutions for customers' specific acidic environments.

Q13: After 5000 hours of QUV accelerated ageing, what does ΔE < 3 mean?

A: ΔE (colour-difference value) is the core indicator for evaluating material colour stability; ΔE < 3 means the colour change is barely perceptible to the naked eye, representing an excellent weathering grade. In QUV accelerated ageing tests, 5000 hours of QUV ≈ about 3–5 years of outdoor exposure (the exact conversion factor varies with regional climate). For example, in real Tiangang customer applications: PP bumper materials with Tiangang® T-78 (light-stabilizer additive package for automotive modification) added show ΔE < 3 and tensile-strength retention > 85% after 5000 hours of QUV testing, meeting the 8-year weathering requirements of mainstream automakers for exterior parts; PE agricultural film with HS-362 added shows elongation-at-break retention > 70% after 5000 hours of QUV testing, corresponding to more than 3 years of field use. Tiangang's Application Technology Center can provide customers with full-chain weathering verification services from accelerated ageing to outdoor exposure.

Related Resources

• Product Center — Browse Tiangang's full product range
• Application Industries — Learn about light stabilizer application solutions across industries
• R&D and Innovation — Explore Tiangang's technical strength and R&D achievements
• Contact Us — Get one-to-one professional consultation

*Document last updated: 9 July 2026. Tiangang reserves the right to update and revise the above content; please refer to the official website for the latest version.*

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