UV Absorber 326 (UV-326): Applications, Dosage, Properties and UV Protection Performance

What Is UV Absorber 326?

Outdoor plastics are continuously exposed to sunlight, heat, oxygen and changing weather conditions. Over time, ultraviolet radiation can accelerate polymer degradation and lead to visible and structural problems such as yellowing, color fading, loss of gloss, surface cracking, brittleness and reduced mechanical strength.

UV Absorber 326, commonly called UV-326, is a benzotriazole-type ultraviolet absorber designed to reduce these damaging effects.

Its function is relatively straightforward: UV-326 absorbs part of the high-energy ultraviolet radiation before that radiation can significantly damage the polymer structure. The absorbed energy is then dissipated in a less harmful form.

As a result, UV-326 can help maintain the appearance and physical performance of polymer products exposed to sunlight.

ECOCHEM recommends UV absorbers for applications including plastics, coatings, adhesives, elastomers and films, while its UV-326 product is particularly associated with PP, PE and PVC applications.

Chemical Composition and Physical Properties of UV-326

UV-326 with CAS No. 3896-11-5 is also known as Bumetrizole.

The authoritative chemical identity associated with CAS 3896-11-5 is:

PubChem identifies CAS 3896-11-5 as Bumetrizole with the molecular formula C17H18ClN3O and molecular weight of approximately 315.8 g/mol.

According to ECOCHEM’s UV-326 specification, the product is supplied as a light yellow to pale yellow powder, with an assay of at least 98% and ash content of no more than 0.1%. ECOCHEM also lists solubility data for solvents including acetone, chloroform, ethyl acetate and n-hexane.

A key characteristic of UV-326 is its UV absorption profile. BASF technical information for Tinuvin 326 shows strong absorption in approximately the 300–400 nm region while maintaining minimal absorption in the visible region above 400 nm. This makes this type of UV absorber particularly useful where UV protection needs to be balanced with product appearance.

Main Applications of UV Absorber 326

One of the major advantages of UV-326 is its compatibility with several important polymer applications.

The following are typical product categories where UV protection is especially important.

1. Polypropylene (PP) Products

Polypropylene is one of the most important application areas for UV-326.

PP is widely used because of its low density, chemical resistance, processing flexibility and favorable cost-performance ratio. However, outdoor PP products can gradually lose their original properties when exposed to UV radiation.

Without sufficient light stabilization, long-term sunlight exposure may contribute to:

• discoloration;
• surface fading;
• loss of gloss;
• embrittlement;
• cracking;
• reduced impact strength;
• shorter outdoor service life.

Adding UV-326 to an appropriate stabilization system helps absorb damaging ultraviolet radiation before it causes extensive photodegradation.

Typical PP applications may include outdoor furniture, storage containers, injection-molded components, automotive parts, industrial housings, garden products and outdoor construction components.

2. Automotive Plastic Components

Modern vehicles use increasingly large quantities of polymer materials.

PP and other thermoplastics can be found in dashboards, interior trim, bumpers, pillar components, consoles, door panels, exterior trims and many other molded components.

Typical application example: automotive interior and injection-molded plastic components.

Automotive plastics may experience a combination of UV radiation, elevated temperature and repeated thermal cycling. These factors make long-term light stability especially important.

UV-326 can be considered as part of the stabilization package for suitable automotive polymers where maintaining color, surface quality and mechanical performance is important.

ECOCHEM specifically lists automotive plastics among its industrial application areas and provides polymer additives intended to improve UV stability, durability and heat resistance.

For demanding outdoor or automotive applications, a UV absorber is often used together with a HALS — Hindered Amine Light Stabilizer. The two technologies operate through different stabilization mechanisms and may provide more comprehensive light protection when properly formulated. ECOCHEM also highlights the complementary use of UV absorbers and HALS.

3. Polyethylene and Agricultural Films

Polyethylene is another important polymer for UV stabilization.

Applications include:

greenhouse film, agricultural covering film, packaging film, industrial film, geomembranes and outdoor PE products.

Typical application example: polyethylene greenhouse and agricultural films exposed to direct sunlight.

Agricultural film presents a particularly demanding environment because the polymer is often thin and continuously exposed to sunlight.

UV degradation may gradually reduce tensile strength and flexibility, eventually contributing to film cracking or premature failure.

ECOCHEM identifies agricultural film as one of its key application markets and discusses stabilization packages combining HALS and UV absorbers for longer film durability. Its agricultural film guidance specifically mentions EcoStab 119 being used with UV-326 and other UV absorbers for more demanding durability requirements.

For agricultural applications, formulation must also consider factors beyond sunlight. Greenhouse films may encounter pesticides, sulfur-containing chemicals, heat and humidity, all of which can influence the performance of the stabilization system.

4. PVC Profiles and Outdoor PVC Products

UV-326 can also be used in appropriate polyvinyl chloride (PVC) formulations.

Typical examples may include:

• window and door profiles;
• outdoor PVC profiles;
• decorative panels;
• PVC sheets;
• outdoor extruded products;
• selected flexible PVC products.

Typical application example: extruded PVC window and construction profiles.

Outdoor PVC products often need to maintain color and surface appearance for years while facing sunlight, heat, moisture and temperature variation.

UV-326 can help reduce the impact of UV radiation, but a complete PVC formulation normally contains several other components, including thermal stabilizers, pigments, lubricants, processing aids and, depending on the product, plasticizers.

Therefore, UV-326 dosage should always be evaluated as part of the entire stabilization package rather than as an isolated ingredient.

ECOCHEM lists PP, PE and PVC among the primary plastics for UV-326 applications.

5. WPC Decking and Building Materials

Wood Plastic Composite, or WPC, has become popular in outdoor flooring, decking, wall panels, fencing and landscaping applications.

Because WPC products are used outdoors, resistance to sunlight and weathering is a major performance requirement.

Typical application example: WPC decking and outdoor composite construction products.

UV exposure can contribute to changes in the appearance of polymer-based construction materials, particularly color and surface condition.

A properly selected UV absorber and light stabilizer package may therefore help outdoor composite materials retain their appearance and physical properties for longer periods.

Building and construction is one of ECOCHEM’s stated application markets, and the company specifically identifies WPC flooring as an application for polymer additives.

6. Coatings, Adhesives and Elastomers

The function of UV-326 is not limited to conventional plastic molding.

Benziazole UV absorbers can also be considered for suitable:

industotrrial coatings, protective coatings, adhesives, sealants, elastomers and related polymer systems.

Typical application example: outdoor protective and industrial coating systems.

For coatings, UV radiation may affect not only the coating itself but also pigments and the substrate underneath.

By reducing UV transmission into the system, a UV absorber may help improve color retention and reduce sunlight-induced degradation.

However, coating formulations can differ significantly in resin chemistry, solvent system, curing technology and film thickness. Dosage therefore needs to be determined specifically for each formulation rather than simply copying the loading used for PP or PE.

ECOCHEM lists coatings and elastomers among its industrial markets and describes UV absorbers as additives for plastics, adhesives, coatings and elastomers.

What Is the Difference Before and After Adding UV-326?

The purpose of UV-326 becomes clearer when comparing a polymer formulation with and without an effective UV stabilization system.

It is important to understand that UV-326 does not make a polymer permanently resistant to aging.

Actual performance is affected by many variables, including:

polymer type, product thickness, color, pigment system, processing conditions, outdoor UV intensity, temperature, geographic location, exposure time and other stabilizers in the formulation.

For high-performance outdoor products, the objective should therefore be to design a complete stabilization system, rather than simply maximizing the concentration of one UV absorber.

Recommended UV-326 Dosage

UV absorbers are normally effective at relatively low concentrations.

According to BASF technical information for Tinuvin 326, recommended concentrations are:

Polypropylene (PP)

0.1%–0.5%

Polyethylene (PE)

0.1%–0.4%

BASF also recommends using Tinuvin 326 in combination with a HALS light stabilizer system.

These values should be treated as formulation reference ranges, not universal fixed recipes.

For example:

A short-life indoor PP component may require a different stabilization package from an outdoor automotive component.

A thick injection-molded PE part will behave differently from a thin agricultural film.

A transparent application may have different requirements from a highly pigmented product.

For this reason, manufacturers should verify the final dosage through tests such as:

QUV accelerated weathering, xenon-arc exposure, color difference testing, tensile strength retention, impact testing and visual surface evaluation.

More UV-326 does not automatically mean better performance.

Excessive additive levels can increase formulation cost and may potentially affect compatibility, migration behavior, appearance or other material properties. The optimum concentration is therefore the amount that achieves the required durability while maintaining processing and economic efficiency.

UV-326 + HALS: A More Complete UV Stabilization Strategy

A UV absorber primarily helps by absorbing damaging UV radiation.

HALS light stabilizers operate through a different mechanism by interfering with photo-oxidative degradation reactions.

Combining these technologies can therefore provide complementary protection.

ECOCHEM describes UV absorbers and HALS as a synergistic combination capable of providing both surface and deeper-layer stabilization.

A typical high-performance formulation may therefore involve:

UV absorber + HALS + antioxidant

rather than relying on a single additive.

This approach is particularly relevant for products expected to operate outdoors for extended periods.

Future Application Opportunities for UV Stabilization Technology

Demand for polymer additives is gradually moving from simply making plastics processable toward making materials more durable, more weather-resistant and capable of maintaining performance for longer periods.

Several emerging areas could create additional demand for UV stabilization technologies.

Recycled and PCR Plastics

As manufacturers increase the use of post-consumer recycled polymers, maintaining consistent long-term performance becomes increasingly important.

Recycled polymer streams may have already experienced thermal or environmental exposure during their previous lifecycle.

Stabilization packages containing UV absorbers, HALS and antioxidants may therefore become increasingly important when developing higher-performance recycled plastic products.

Electric Vehicles and Charging Infrastructure

Electric vehicles use a wide range of polymer components, while outdoor charging equipment introduces additional applications for weather-resistant housings, connectors and polymer structural components.

Lightweighting trends can further increase the importance of durable polymer materials.

Smart Outdoor Equipment

Outdoor sensors, telecommunications equipment, smart-home devices, solar-system components, electrical housings and IoT devices all require materials capable of surviving prolonged environmental exposure.

Advanced Agricultural Films

The agricultural industry continues to demand films with longer service life and multiple functions such as light diffusion, anti-fog performance, thermal management and controlled light transmission.

UV stabilization will remain an important part of these multifunctional film systems.

Durable Building Materials

WPC decking, cladding, plastic profiles, fencing, roofing components and outdoor decorative materials increasingly need to retain both appearance and mechanical performance over long service periods.

Regulatory Considerations for UV-326

Regulatory compliance should be evaluated before selecting UV-326 for a new application.

In the European Union, Bumetrizole (UV-326), CAS 3896-11-5, was added to the REACH Candidate List of Substances of Very High Concern on January 23, 2024 because it meets the criteria for a very persistent and very bioaccumulative substance (vPvB).

As of 2026, ECHA’s prioritisation assessment has also proposed UV-326 for recommendation for inclusion in REACH Annex XIV.

Therefore, companies supplying products to the EU or other regulated markets should confirm the latest legal requirements, customer specifications and end-use restrictions before adopting UV-326.

Regulatory suitability should be evaluated separately from technical performance.

Why Choose ECOCHEM for UV-326?

Choosing a UV absorber supplier involves more than purchasing a chemical with the correct CAS number.

Reliable industrial production also depends on consistent quality, technical understanding, formulation flexibility and a stable supply chain.

More Than 10 Years of Polymer Additive Experience

ECOCHEM has served the polymer additives industry since 2014, focusing on anti-aging solutions for polymer materials. Its portfolio includes UV absorbers, HALS light stabilizers, antioxidants, polymerization inhibitors, chemical intermediates and other specialty additives.

More Than 100 Polymer Additives

ECOCHEM states that it offers more than 100 polymer additives, allowing customers to source multiple stabilization technologies through one supplier.

This is particularly useful when a formulation requires more than UV-326 alone.

For example, a customer developing an outdoor PP component may need to evaluate:

UV-326 + HALS + antioxidant

as a complete system.

Samples for Formulation Testing

ECOCHEM provides complimentary small samples for pre-purchase testing, allowing customers to evaluate additives in their own polymer formulations before moving to commercial quantities.

For polymer additives, this is particularly important because the optimum solution depends strongly on the resin, processing method and final application.

Multiple Application Markets

ECOCHEM works with polymer additives for agricultural films, automotive plastics, packaging, artificial grass, building and construction, coatings and elastomers.

This application-focused approach makes it easier to select not only an individual UV absorber but also a more complete anti-aging package.

One-Stop Polymer Additive Supply

For manufacturers using several additive categories, sourcing UV absorbers, HALS, antioxidants and other specialty additives from one supplier can simplify procurement and formulation development.

That is one of the core reasons to choose ECOCHEM as your UV-326 and polymer additive supplier in China.

Conclusion

UV Absorber 326 (UV-326) is a well-established benzotriazole UV absorber used to improve the light stability of polymer materials.

It is particularly suitable for polyolefin applications such as PP and PE, while it may also be considered for appropriate PVC products, automotive plastics, agricultural films, construction materials, coatings and other polymer systems.

Typical reference dosage ranges are approximately:

PP: 0.1%–0.5%

PE: 0.1%–0.4%

When properly formulated, UV-326 can help delay yellowing, fading, gloss loss, embrittlement, cracking and deterioration of mechanical properties caused by UV exposure.

For demanding outdoor applications, combining a UV absorber with HALS and antioxidants can provide a more comprehensive stabilization strategy.

With more than a decade of polymer-additive experience, a broad product portfolio and sample support for formulation testing, ECOCHEM provides UV-326 as part of a complete range of anti-aging solutions for plastics and polymer materials.

Looking for UV-326 for your formulation?

Whether you manufacture PP products, PE films, PVC profiles, automotive plastics, agricultural films, WPC materials or industrial coatings, ECOCHEM can help you evaluate the appropriate UV stabilization solution.

Contact ECOCHEM for UV-326 samples, technical information, pricing and formulation recommendations.

FAQ: UV Absorber 326

What is UV-326 used for?

UV-326 is used to absorb damaging ultraviolet radiation and improve the weathering stability of polymers. Typical applications include polypropylene, polyethylene, selected PVC products, automotive plastics, agricultural films and other outdoor polymer products.

How much UV-326 should be added to PP?

A typical reference dosage for polypropylene is approximately 0.1%–0.5%, although the optimum concentration should be determined according to the resin, product thickness, outdoor exposure and target lifetime.

How much UV-326 should be added to PE?

For polyethylene, a typical reference concentration is approximately 0.1%–0.4%.

Can UV-326 be used with HALS?

Yes. Combining UV-326 with an appropriate HALS can provide complementary stabilization. This approach is often preferable for demanding outdoor applications.

Is UV-326 suitable for the EU market?

UV-326 is currently listed on the EU REACH Candidate List as an SVHC due to its vPvB properties. Companies should therefore verify current REACH obligations, customer requirements and the intended application before use in products for the EU market.