UV-Resistant Plastics: Which Polymers Need UV Stabilizers, 12 Polymers Compared

A UV-resistant plastic is a plastic that keeps its mechanical strength, its colour and its surface gloss in sunlight, and of the 12 polymer families used outdoors only 3 manage it without a light stabilizer: PMMA, ASA and the fluoropolymers. The other 9 need an additive package, which raises the two questions this page answers: how sensitive is each polymer, and what does it take to make it resistant?

Sunlight at the Earth's surface starts at 280 to 290 nm, while aliphatic polyolefins absorb nothing above about 250 nm, so photo-oxidation never begins with the polymer backbone. It begins at the chromophores every commercial resin carries: hydroperoxides, carbonyl groups and titanium and iron catalyst residues. About 70 % of the world's light stabilizers go into polyolefins, which are about 50 % of plastics production, which is why polypropylene and polyethylene dominate this group of plastic additives.

This page separates "UV resistant" as a material property from "UV stabilized" as a formulation fact, ranks the 12 polymer families by UV sensitivity, sets out the 5 additive routes and the loading range in wt%, explains the weathering tests and the four properties that prove the claim, and closes with the food-contact limits and the producers behind the compounds.

Four figures that set the scale of the UV question

• 280 to 290 nm: the shortest sunlight wavelength that reaches the Earth's surface.
• 0.05 to 1.4 wt%: the usual light-stabilizer loading in plastics, from thick sections to polypropylene fibres.
• 3 of 12: polymer families that resist sunlight without an additive, counted from the ranking below.
• About 70 %: share of the world's light-stabilizer production that goes into polyolefins.

What Does "UV Resistant" Mean for a Plastic?#

UV resistance is a plastic's ability to keep its mechanical strength, colour and surface gloss under sunlight, measured as the change in elongation, yellowness index and gloss after a defined radiant dose. The properties that move are always the same seven: chalking, surface crazing, gloss loss, yellowing, colour difference, embrittlement and loss of elongation at break. The industry buys that resistance with 5 classes of UV stabilizers, namely UV absorbers, hindered amine light stabilizers, excited-state quenchers, hindered benzoates and UV screeners. Construction specifications call the same additive a UV inhibitor.

Is that resistance a property of the polymer or of the formulation? It is both. The classes, mechanisms and grades of UV stabilizers for plastics are compared on the family hub, while this page stays with the host polymer and asks which resins need them.

UV Resistant vs UV Stabilized: What Is the Difference?#

"UV resistant" describes how a material behaves in sunlight, while "UV stabilized" states that light stabilizers were compounded into it, so a UV-stabilized polypropylene is resistant only because of its hindered amine package and an unstabilized one is not resistant at all. "Light stabilizer" is the umbrella term in the BASF and Syensqo catalogues, "UV stabilizer" is the dominant trade and search term, and a European datasheet that reads "UV stabilised" is making the same formulation claim in British spelling. Only one of the two can be verified from the polymer alone: ASA is weatherable because its saturated acrylate rubber carries no double bonds, and PMMA is inherently UV-stable, so neither claim depends on an additive.

Table 1. "UV resistant" and "UV stabilized" compared

For a buyer the practical consequence sits in the second column. A datasheet that says "UV stabilized" should be read together with the stabilizer class, the loading and the weathering data, because the phrase on its own says only that something was added. A datasheet that says "UV resistant" with neither a test method nor a retained property is not a specification at all.

Why Is No Plastic Completely UV Resistant?#

No plastic is completely UV resistant because every commercial resin carries chromophores that the pure polymer does not have: hydroperoxides, carbonyl groups and titanium and iron catalyst residues absorb the 280 to 290 nm sunlight that reaches the ground and start a radical chain reaction with oxygen. Light is one of three routes to polymer degradation, next to heat and shear, and the only one that needs an absorbing species first. Aliphatic polyolefins absorb only below about 250 nm, so a pure polyethylene chain in sunlight would be inert.

The photo-oxidation cycle runs in 4 steps.

1. An alkyl radical reacts with oxygen to form a peroxy radical (R• + O2 → ROO•).
2. The peroxy radical abstracts hydrogen from the chain, giving a hydroperoxide and a new alkyl radical (ROO• + RH → ROOH + R•).
3. The hydroperoxide splits under light into an alkoxy and a hydroxyl radical (ROOH + hv → RO• + •OH).
4. The alkoxy radical beta-scissions into a ketone and a macroradical, and the ketone photolyses by Norrish type II scission at ambient temperature.

The effect of temperature on photo-oxidation is often greater than the effect of UV dose, in the Arrhenius sense, so the same radiant dose does more damage on a hot black surface than on a cool white one. The full chemistry of photodegradation of plastics is set out polymer by polymer on its own page.

How Do You Tell That a Plastic Is Failing in Sunlight?#

A plastic failing in sunlight shows 7 signs: chalking, surface crazing, gloss loss, yellowing, colour change, embrittlement and loss of elongation at break.

• Chalking: a loose powdery layer of degraded polymer and exposed pigment at the surface.
• Surface crazing: a network of fine cracks in the outer skin, before any bulk failure.
• Gloss loss: a drop in specular reflectance as the surface roughens.
• Yellowing: a rise in yellowness index, measured to ASTM E313-20.
• Colour change: a colour difference against the unexposed reference, to ASTM D2244-25.
• Embrittlement: brittle fracture at loads the unexposed part carried.
• Loss of elongation at break: the property that falls first in films, tapes and fibres.

Two further signals never show on the surface. Melt flow rate rises in polymers that chain-scission, polypropylene above all, while polyethylene crosslinks instead and forms gels. Yellowing has causes other than sunlight, and why plastics turn yellow separates photo-oxidation from phenolic gas fading, titanium-driven pinking and overheating in the extruder.

Is a UV-Resistant Plastic Also a UV Blocker?#

No: a UV-resistant plastic survives sunlight, while a UV-blocking plastic stops sunlight from passing through it, and the two are different jobs solved with different additives. One protects the polymer; the other protects the contents.

Blocking is a Beer-Lambert problem, which means the UV stopped grows with concentration multiplied by path length. A formulator solves it with UV absorbers at high loading, with a UV-screening pigment, or with a thicker wall: benzotriazoles cover 300 to 400 nm and the hydroxyphenyl triazine Tinuvin 1577 covers 280 to 350 nm, carbon black absorbs across the whole solar spectrum, and rutile titanium dioxide screens UV while making the part opaque. The familiar examples are UV-barrier PET and polycarbonate packaging and white titanium-dioxide-pigmented PET dairy bottles. PMMA shows the distinction at its clearest: acrylic transmits 92 % of visible light at 3 mm and takes UV absorbers mainly to protect whatever sits behind the sheet.

Which Plastics Need UV Stabilizers and Which Do Not? 12 Polymers Ranked#

Of the 12 polymer families used outdoors, polypropylene needs the most UV stabilizer and the fluoropolymers need none, with the dividing line running between the polymers whose backbone or normal impurity set absorbs sunlight above 290 nm and the 3 that carry no usable chromophore at all. Three questions decide the order, and stating them makes the ranking auditable: does the polymer or its impurity set absorb sunlight above 290 nm, does oxidation cut the chain or crosslink it, and does any supplier publish a light-stabilizer loading for it at all.

The ranking runs from most sensitive to least sensitive, because the question it answers is which resin needs help first. The complete formulation guide for each resin sits under additives by polymer.

Table 2. The 12 polymer families ranked by UV sensitivity

Loadings are supplier technical-datasheet ranges for the named grades, not specifications; trials decide the final level. Where a cell is empty, no verified loading exists in our sources.

1. Polypropylene (PP)#

Polypropylene is not UV resistant: every second carbon in its backbone carries a tertiary C-H bond, the weakest point for photo-oxidation, which makes PP the most light-sensitive commodity polyolefin and gives it the highest hindered-amine loadings of any plastic. Oxidation at that tertiary carbon is followed by beta-scission, so the chains get shorter, the melt flow rate rises and the part embrittles from the surface inward. The mechanism is the reason PP and PE fail differently from the same exposure even though both start from impurity-initiated attack.

Loadings follow section thickness rather than the polymer grade. Oligomeric HALS run 0.05 to 1.0 wt% in thick sections, 0.1 to 1.0 wt% in films and 0.1 to 1.4 wt% in PP fibres, the highest light-stabilizer level in commodity plastics, with a UV absorber added in unpigmented parts. Grade-by-grade dosage for fibres, tapes, film, thick sections and automotive TPO is on UV stabilizers for polypropylene.

2. Polystyrene, HIPS and EPS#

Polystyrene is not UV resistant: it yellows through polyene and acetophenone-type chromophores, a route identified by Rabek and Ranby in 1974, and high-impact polystyrene yellows faster still because its butadiene rubber phase oxidises on top of the styrene chemistry. Atactic polystyrene has a glass transition temperature of about 90 °C, so a black exposed part also runs close to its softening range.

The route for the styrenics is a low-molecular-weight HALS such as Tinuvin 770 or Uvinul 4050 at 0.05 to 1.0 wt% together with a benzotriazole UV absorber such as UV-P or Tinuvin 234 at 0.1 to 0.5 wt%. Expanded and extruded polystyrene outdoors is mostly a flame-retardant and facade-render question rather than a light-stabilizer one. The full package for GPPS, HIPS, EPS and XPS is on additives for polystyrene.

3. ABS and SAN#

ABS is not UV resistant: its butadiene rubber phase, 5 to 30 % of the compound, oxidises under sunlight and forms coloured polyenes, so unstabilized ABS yellows and chalks outdoors. The rest of the compound is 15 to 35 % acrylonitrile and 40 to 60 % styrene, with a glass transition temperature of about 105 °C, and none of it is the problem: the double bonds in the rubber are.

A low-molecular-weight HALS at 0.05 to 1.0 wt% plus a benzotriazole at 0.1 to 0.5 wt% slows the yellowing, and that is the usual answer for a part with intermittent exposure. For a permanently exposed part the standard engineering answer is a change of resin rather than a change of additive, to ASA, whose saturated acrylate rubber gives about 10 times the weathering resistance of ABS, as section 10 of this ranking sets out. Grades and loadings for the styrenics sit on UV stabilizers for ABS.

4. Polyamide (Nylon PA6 and PA66)#

Polyamide is poorly UV resistant: PA6 and PA66 yellow and lose elongation outdoors, and the choice of light stabilizer is constrained by the copper halide heat stabilizers that most heat-aged nylon grades already contain, typically 0.001 to 0.03 wt% copper with 0.1 to 5 wt% halide, a system patented by DuPont in US 2,705,227 in 1954. PA6 melts at 215 to 218 °C and PA66 at 264 °C, so the additive also has to survive a hot melt.

The oxanilide Tinuvin 312 is the standard answer in nylon for three reasons at once: it absorbs most strongly in UV-B, its technical datasheet credits it with added thermal stability in polyamide, and it does not interact with the copper systems. Oxanilide loadings run 0.10 to 1.0 wt%, with Tinuvin 770, Uvinul 4050, Tinuvin 622, Chimassorb 944 and the benzotriazole Tinuvin 234 as the alternatives. One hindered amine is listed for polyamide food contact in the EU, CAS 42774-15-2, FCM 1051, with a specific migration limit of 5 mg/kg. The oxanilide and copper-compatibility questions are covered on UV stabilizers for nylon.

5. Polyurethane and TPU#

Polyurethane is poorly UV resistant when it is aromatic: the MDI-based segments yellow through quinone-imide formation, while aliphatic polyurethanes hold their colour far better. Photo-Fries rearrangement applies to those aromatic segments as it does to polycarbonate and the aromatic polyesters, so the yellowing is a backbone reaction rather than a rubber-phase one.

Light stabilizers reach polyurethane and TPU as liquids, because the base chemistry is metered rather than compounded: a liquid benzotriazole at 0.2 to 0.5 wt% in PU, or a formamidine UV absorber at 0.5 to 3.0 wt% on solids together with 0.5 to 2.0 wt% HALS in polyurethane and epoxy systems. Tinuvin 144 and Tinuvin 765 are used here as well, and ready-made liquid PU stabilizer packages supply absorber and hindered amine in one addition. Isocyanates, polyols and the amine or tin catalysts sit outside the additive scope of this site. The liquid stabilizer packages used in PU and TPU are on UV stabilizers for polyurethane.

6. Polyethylene (HDPE, LDPE and LLDPE)#

Polyethylene is not UV resistant unpigmented, is largely UV resistant with carbon black: unpigmented PE degrades through the same impurity-initiated photo-oxidation as polypropylene, while black PE pressure pipe at 2.0 to 2.5 % carbon black by mass is specified for buried and exposed service. A single adjective describes neither the natural film nor the black pipe correctly.

Polyethylene crosslinks and forms gels as it oxidises rather than cutting chains, so the first symptoms are gels and surface cracking rather than a rising melt flow rate. Oligomeric HALS cover the unpigmented case at 0.05 to 0.6 wt% in thick sections and 0.1 to 1.0 wt% in LDPE and LLDPE film. Film, pipe and rotomoulding grades are on UV stabilizers for polyethylene.

Two published specifications make the carbon-black half of the verdict measurable. PE pressure pipe to EN 12201-1 and ISO 4427-1:2019 carries 2.0 to 2.5 % carbon black by mass at an average primary particle size of 10 to 25 nm, dispersion grade 3 or better to ISO 18553, and an oxidative induction time of at least 20 minutes at 210 °C. HDPE geomembrane to GRI-GM13 Rev. 16, dated 17 March 2021, carries 2.0 to 3.0 % carbon black and must retain at least 50 % of its high-pressure oxidative induction time after 1,600 hours of UV exposure.

7. Polycarbonate (PC)#

Polycarbonate is poorly UV resistant unprotected: the carbonate group rearranges under UV in a photo-Fries reaction and the surface yellows, which is why outdoor PC glazing carries a co-extruded cap layer rather than a bulk stabilizer. Polycarbonate also has a glass transition temperature of 147 °C and hydrolyses above 70 °C at high humidity, releasing bisphenol A, so heat and moisture act on the same exposed sheet.

The quantitative reason for the cap layer is Beer-Lambert arithmetic. Benzotriazole UV absorbers reach 5 to 10 wt% in a co-extruded cap layer against 0.1 to 0.5 wt% in the bulk, so a thin surface layer stops far more UV where the light actually arrives than a bulk loading of 0.3 wt% ever could, at a fraction of the additive cost. The grades that survive polycarbonate processing are Tinuvin 360 at 0.2 to 1.0 wt%, Tinuvin 1577, Tinuvin 1600, Tinuvin 234 and Uvinul 3030. The market experiences PC glazing as UV resistant because of that construction, not because the polymer is. Cap-layer loadings and the triazine grades for PC are on UV stabilizers for polycarbonate.

8. PVC#

PVC is partly UV resistant: the pure polymer absorbs nothing above 220 nm, so sunlight attacks only its structural defects, hydroperoxides and carbonyl groups, but the HCl released when it does deactivates conventional hindered amine light stabilizers and leaves UV absorbers, titanium dioxide and NOR HALS as the usable routes. Colour appears once polyenes reach 8 or more conjugated C=C bonds. Conventional N-H and N-methyl hindered amines are largely ineffective in vinyl because that HCl protonates them, a limitation documented by Capocci and Hubbard in the Journal of Vinyl and Additive Technology in 2005. Why hindered amines fail in vinyl, and what replaces them, is explained on UV stabilizers for PVC.

White PVC window profiles behave well outdoors for a reason unrelated to hindered amines: rutile titanium dioxide screens UV in the surface layer of a heavily pigmented formulation. Basicity explains the rest, measured as pKb: N-H grades sit at about 4 to 5 and N-methyl at about 5 to 6, while NOR HALS at about 8 to 10 keep working where the basic grades are protonated, which is why flexible roofing membranes use them. The titanium dioxide and impact-modifier package behind white profiles is on additives for PVC window profiles.

Exposed pipe and conduit are a separate case, handled on additives for PVC pipe. The absorber route in vinyl runs on benzophenones, the liquid benzotriazole Tinuvin 571 at 0.3 to 0.5 wt% and up to 5 wt% in cap layers, the oxanilide Tinuvin 312 and the cyanoacrylates Uvinul 3035 and 3039.

9. PET and PBT#

PET is partly UV resistant: it absorbs from 360 nm and strongly below 320 nm, so the polymer itself takes the energy, and the practical limit on stabilizing it is not chemistry but volatility, because the additive has to survive 270 to 300 °C processing. Norrish type I scission dominates the degradation and type II releases acetaldehyde, which is a packaging-taste problem as well as a mechanical one.

Volatility therefore selects the grade, and the numbers are unambiguous. Measured by thermogravimetric analysis at 1 % mass loss, UV-P leaves at 153 °C and UV-328 at 183 °C, while Tinuvin 234 holds to 264 °C, Tinuvin 1577 to 300 °C and UV-360 to 333 °C, which is why the hydroxyphenyl triazines and the benzoxazinone Cyasorb UV-3638 own this polymer. Cyasorb UV-3638 is positioned by its supplier at about one third of a benzotriazole loading. The usual application is UV-barrier packaging that protects the contents, plus fibres. The low-volatility grades that survive PET processing are listed on UV stabilizers for PET.

10. ASA#

ASA is largely UV resistant: replacing the butadiene rubber of ABS with a saturated acrylate rubber removes the double bonds that oxidise, and the result is about 10 times the weathering resistance of ABS. That figure is a secondary-source value and the word "about" belongs with it, but the structural reason behind it is not in doubt.

Better weathering resistance of the rubber phase is not the same thing as colour stability of the whole compound, so pigmented ASA for permanent exposure still carries a UV absorber for colour retention rather than for mechanical protection. The complete comparison of the three styrenic copolymers is on additives for ABS, SAN and ASA, which covers where each of them belongs outdoors.

11. PMMA (Acrylic)#

PMMA is largely UV resistant: acrylic is inherently UV-stable, which is why it holds 92 % visible-light transmission at 3 mm in outdoor glazing, and the UV absorbers added to it protect whatever sits behind the sheet rather than the acrylic itself. The grades used for that job are UV-P, Tinuvin 234 and Tinuvin 360, and the glass transition temperature of the base polymer is 105 °C, with commercial grades spanning 85 to 165 °C.

Inherent UV stability does not mean an acrylic part cannot fail, because the pigments, the impact modifiers and the mounting system each age at their own rate. The methyl methacrylate monomer carries an EU group restriction of 6 mg/kg in food-contact use, which is a migration question rather than a weathering one. Which absorbers go into acrylic sheet and why is covered on UV stabilizers for PMMA (acrylic).

12. Fluoropolymers and High-Temperature Polymers (PTFE, PVDF, PPS)#

Fluoropolymers are largely UV resistant in the only sense this page can verify: no light-stabilizer supplier in our sources publishes a UV dosage for PTFE, PVDF or ETFE, which is the clearest industry signal that these polymers are not stabilized against sunlight. Our knowledge base holds no weathering data, no retained-property figure and no loading for any of the three, so this section states the boundary of the evidence instead of filling it.

PPS is the counter-example inside the same group. It survives a service temperature up to 240 °C yet is difficult to UV-stabilize, because conventional UV absorbers are disrupted by the acids and bases in the matrix, and the 240 to 320 °C processing window of the engineering polymers rules out most low-molecular-weight additives in the first place. The additive constraints of the 240 to 320 °C polymers are set out under additives for high-performance polymers.

What Makes a Plastic UV Resistant? 5 Additive Routes#

The 5 routes to a UV-resistant plastic are hindered amine light stabilizers, UV absorbers, UV-screening pigments, a co-extruded cap layer and the antioxidant package underneath them, and the first two carry most of the protection in most polymers. The order is the order of how much protection each route delivers across the 12 polymer families above, and it is the order this page keeps in every list and table.

Grouping them this way follows what a formulator actually does rather than how the chemistry is classified, so the two minor chemical classes, the excited-state quenchers and the hindered benzoates, are named inside the hindered amine and absorber sections rather than being dropped.

1. Hindered Amine Light Stabilizers (HALS)#

Hindered amine light stabilizers are 2,2,6,6-tetramethylpiperidine derivatives that make a plastic UV resistant by trapping the radicals of photo-oxidation and regenerating themselves in the Denisov cycle, and they absorb almost no UV light at all. The amine is oxidised to an aminoxyl radical that traps alkyl radicals; the aminoether formed reacts with peroxy radicals and releases the aminoxyl radical again, a loop described by E. T. Denisov in Polymer Degradation and Stability 34 (1991) 325-332, worked out energetically by Jennifer Hodgson and Michelle Coote at the Australian National University in Macromolecules 43 (2010) 4573, and reviewed by Pieter Gijsman in Polymer Degradation and Stability 145 (2017) 2-10. Because the aminoxyl radical returns to the cycle, a hindered amine is not consumed in proportion to the UV dose, and its protection does not depend on part thickness.

Where they fail is a question of basicity. Conventional N-H and N-methyl grades sit at a pKb of about 4 to 6 and are switched off by acids, while N-alkyl polyester grades at about 7 to 8 and N-OR grades at about 8 to 10 survive them. Two minor classes complete the taxonomy: nickel quenchers such as UV-1084 (CAS 14516-71-3) drain energy from excited chromophores by Förster transfer in mulch film, and hindered benzoates such as Cyasorb UV-2908 rearrange under light into benzophenone-type absorbers at 0.1 to 0.5 wt% in thick-section PP. Basicity, molecular weight and grade data for all hindered amine light stabilizers (HALS) sit on the HALS node.

2. UV Absorbers#

UV absorbers make a plastic UV resistant by converting UV photons into harmless heat through an excited-state intramolecular proton transfer, and because they follow the Beer-Lambert law their protection grows with concentration multiplied by path length. J. Crawford set out that energy-dissipation route in Progress in Polymer Science 24 (1999) 7-43. Six chemical classes do the work, namely benzotriazoles, 2-hydroxybenzophenones, hydroxyphenyl triazines, oxanilides, cyanoacrylates and benzoxazinones, and their windows differ: benzotriazoles cover 300 to 400 nm, the hydroxyphenyl triazine Tinuvin 1577 covers 280 to 350 nm, and the oxanilide Tinuvin 312 is strongest in UV-B. All six chemical classes of UV absorbers are compared by absorption range and volatility on the dedicated node.

The thickness term in Beer-Lambert decides formulations more often than the chemistry does. A loading of 0.1 to 0.5 wt% absorbs a useful fraction of the UV through a 3 mm wall and almost none through a 25 µm film, which is why films get hindered amines and thick clear parts get both classes. Coatings show the arithmetic at its clearest, with absorber levels falling from 2.5 to 5 % at 10 to 20 µm dry film thickness to 0.5 to 1.25 % at 40 to 80 µm, a coatings figure quoted only for scale. The grade set that dominates plastics, the benzotriazole UV absorbers, has its own node.

3. UV Screeners: Carbon Black, Titanium Dioxide and Zinc Oxide#

UV screeners make a plastic UV resistant by stopping the light in the outer layer of the part, and carbon black is the most effective of them for polyethylene and polypropylene because it absorbs across the whole solar spectrum. Particle size sets the balance: black PE pressure pipe to ISO 4427-1:2019 specifies an average primary particle size of 10 to 25 nm at 2.0 to 2.5 % by mass, HDPE geomembranes to GRI-GM13 carry 2.0 to 3.0 %, and smaller primary particles screen better but disperse less easily. Carbon black, titanium dioxide and zinc oxide are compared as UV screeners on their own node.

Rutile titanium dioxide does two jobs with one high refractive index, scattering visible light for opacity and screening UV, and it brings one trap with it. A rutile grade with little surface treatment can over-oxidise the phenolic antioxidant in the same compound into coloured titanium-quinone complexes, which shows up as pinking or yellowing in a white part and is mitigated with zinc stearate. Grades, particle sizes and food-contact limits are on carbon black in plastics, with the EU cap of 2.5 % w/w under FCM 411 and the US limit of 2.5 % by weight for high-purity furnace black under 21 CFR 178.3297.

Zinc oxide absorbs and scatters UV as well and is the third screening pigment, though our sources carry no plastics loading for it. Rutile grades and the pinking interaction are on titanium dioxide in plastics.

4. Co-Extruded Cap Layers and UV Masterbatch#

A co-extruded cap layer makes a plastic UV resistant by concentrating the UV absorber where the light arrives, which is why cap layers carry 5 to 10 wt% benzotriazole while the bulk of the same part carries 0.1 to 0.5 wt%. Outdoor polycarbonate glazing is built exactly that way, and PVC profile and sheet use the same route at up to 5 wt% in the cap layer, which converts a Beer-Lambert problem into a geometry problem.

Delivery form is the second half of the question, because most converters add light stabilizers as masterbatch rather than as neat powder, and the loading then follows a let-down calculation. As a calculation example, a 20 wt% HALS masterbatch added at 2.5 % gives 0.5 wt% active stabilizer in the part, since 0.20 × 2.5 % = 0.5 %. Check the arithmetic for any concentrate and target level in the let-down ratio calculator.

5. Antioxidants and Acid Scavengers as the Supporting Layer#

Antioxidants are the layer under every UV package: a phenolic antioxidant and a phosphite protect the polymer in the extruder, and no light stabilizer replaces them, because hindered amines are weaker than phenolics during melt processing. Gensler and co-workers established that split in 2000, and Gijsman and Fiorio confirmed it in Polymer Degradation and Stability 208 (2023) 110260. The polyolefin base package is therefore a phenolic antioxidant plus a phosphite for processing, a thioester for long-term heat and an acid scavenger, either calcium stearate up to 1,000 ppm or a hydrotalcite, with the hindered amine and the absorber on top for outdoor service. Irganox 1010 runs 0.05 to 0.4 wt% and Irgafos 168 0.05 to 0.2 wt%. The phenolic and phosphite layer under every UV package is covered under antioxidants for plastics.

Three antagonisms inside that package change the light stabilizer's dosage: thioesters antagonise hindered amines through their acidic sulfur oxidation products, halogenated flame retardants and acidic pigments deactivate the basic grades, and talc adsorbs the antioxidant on its acidic surface sites. The mirror image of the system is the oxo-degradable additive, built on iron, manganese and cobalt salts that accelerate photo-oxidation deliberately through hydroperoxide homolysis. Synergy and antagonism across all families are mapped under additive interactions.

How Much UV Stabilizer Does a Plastic Need to Be UV Resistant?#

A plastic needs 0.05 to 1.4 wt% light stabilizer to be UV resistant in most applications, with the exact level set by section thickness, pigmentation, the solar dose where the part is used and the required service life. Across the 16 light stabilizers registered above 100 t/yr in the ECHA plastic additives mapping, the typical band runs wider still, from 0.0015 to 6.0 wt%.

Four drivers move a formulation inside those ranges.

• Section thickness, and whether the light reaches a surface or has to be stopped through a bulk wall.
• Pigmentation, since carbon black screens UV on its own while organic pigments such as copper phthalocyanine can sensitise the polymer.
• The radiant dose at the site of use and the service life the part has to reach there.
• The rest of the additive package, since thioesters, acidic flame retardants and talc all raise the level needed.

Typical loadings for every family are collected under additive dosage levels in plastics, which puts the light-stabilizer band next to the antioxidant and filler levels in the same recipe.

Table 3. Light-stabilizer loading by class and application

Supplier technical-datasheet ranges; trials decide the final level. The limits in 21 CFR 178.2010 and Regulation (EU) No 10/2011 are legal maxima, not dosages.

A 20 wt% hindered amine masterbatch let down at 2.5 % puts 0.5 wt% of active stabilizer in the finished part, the same final level a formulator reaches by dosing neat powder, and that calculation, together with an additive dosage and cost-in-use calculator, is the only sound way to compare two concentrate offers. Formulators should treat the caps in 21 CFR 178.2010 as legal maxima rather than as recommended loadings, because those figures limit migration into food and say nothing about weathering performance.

How Is the UV Resistance of a Plastic Tested?#

The UV resistance of a plastic is tested by exposing specimens in a xenon-arc or fluorescent-UV cabinet or outdoors, then reporting the retained property after a stated radiant dose, which is what turns "UV resistant" from a claim into a specification. Cycle details, lamp types and specimen handling are on accelerated weathering tests, and the three sections below cover the laboratory exposure, the outdoor dose and the four properties worth measuring.

Accelerated Weathering: Xenon Arc and Fluorescent UV#

Xenon-arc testing to ISO 4892-2 Method A cycle 1, which runs 102 minutes of light and 18 minutes of water spray at 0.51 W/(m²·nm) at 340 nm with a black standard temperature of 65 ± 3 °C, is the closest laboratory match to outdoor sunlight. The chamber runs at 38 ± 3 °C and 50 ± 10 % relative humidity. ASTM G155-25 is the current xenon practice and recommends two control materials, while ASTM D2565 is the plastics practice and is not equivalent to ISO 4892-2. Fluorescent UV sits on a different cycle: ASTM G154-23 cycle 4 uses UVA-340 lamps at 1.55 W/m² at 340 nm with 8 hours of UV at 70 °C and 4 hours of condensation at 50 °C, about 3 times AM1.5 sunlight at 340 nm, and ASTM D4329-26 is the plastics version.

Table 4. Weathering methods and their conditions

What a cabinet does not reproduce matters as much as what it does. Laboratory weathering simulates neither pollution, nor biological attack, nor salt water, and because temperature often outweighs UV dose, two laboratories can disagree about the same material when their black standard temperatures differ. The GRI-GM13 geomembrane requirement is the clearest pass criterion in our sources, at 1,600 hours with at least 50 % retained high-pressure oxidative induction time.

Outdoor Exposure and Radiant Dose (kLy)#

Outdoor UV exposure is counted as radiant dose in kilolangleys, where 1 kLy equals 1,000 langley, 1,000 cal/cm² or 41.84 MJ/m², which is about 11.6 kWh/m². The same stabilized part therefore reaches its dose at a different rate in Northern Europe and in the Gulf, and a specification that names a service life without naming a site has specified nothing.

Annual dose varies strongly between locations, and our sources do not yet carry a cross-checked regional table, so this page gives the unit and not a map. Dose is also not the whole exposure: surface temperature runs alongside it and often outweighs it, which is why outdoor racks record both. Radiant exposure (UV dose) has its own glossary entry with the conversions between langley, MJ/m² and kWh/m².

What to Measure: Yellowness Index, Elongation, Carbonyl Index and Melt Flow Rate#

The 4 properties that prove UV resistance are yellowness index to ASTM E313, elongation at break to ISO 527, carbonyl index by FTIR and melt flow rate to ISO 1133.

• Yellowness index: ASTM E313-20 (2025 edition), valid for a dominant wavelength of 570 to 580 nm; colour difference goes to ASTM D2244-25.
• Elongation at break: ISO 527-1 and ISO 527-2, or ASTM D638-22, with film below 1 mm measured to ASTM D882.
• Carbonyl index: an FTIR band ratio, used as a direct measure of accumulated oxidation.
• Melt flow rate: ISO 1133-1 or ASTM D1238-26, at 230 °C and 2.16 kg for PP and 190 °C and 2.16 kg for PE.

Which of the four to use follows the part: yellowness for clear and light-coloured parts, elongation for films, tapes and fibres, carbonyl index for research and failure analysis, and melt flow rate when the polymer chain-scissions. How the yellowness index is calculated, and why the withdrawn ASTM D1925 is never cited as current, is explained on its own page, as tensile testing of plastics covers the elongation methods.

A rising melt flow rate is the signature of chain scission, and gels are its counterpart in polyethylene. No pass or fail value exists in our sources for any polymer except the GRI-GM13 criterion, so the end point comes from the product specification, and carbonyl index has its own page for the FTIR calculation.

How Long Does UV-Resistant Plastic Last Outdoors?#

No single outdoor lifetime applies to UV-resistant plastic: service life is set by the polymer, the stabilizer package, the pigment, the wall thickness, the local radiant dose and the surface temperature, which is why real specifications state a retained property after a stated exposure instead of a number of years. A figure in years for a polymer family is not a material property, and this page publishes none.

Two documented criteria show how the industry does state it. An HDPE geomembrane to GRI-GM13 Rev. 16, dated 17 March 2021, must retain at least 50 % of its high-pressure oxidative induction time after 1,600 hours of UV exposure. A black PE pressure pipe compound to ISO 4427-1:2019 must carry 2.0 to 2.5 % carbon black by mass and reach an oxidative induction time of at least 20 minutes at 210 °C. Both are retained-property statements with a defined exposure, verifiable on a sample.

What shortens service life is often chemistry rather than light. Greenhouse film loses 20 to 25 % of its life when the sulfur residue from pesticides doubles from about 1,000 to 2,000 ppm, a result reported at the AMI Agricultural Films conference in 2010, and growers in Spain and Morocco see residues above 1,500 ppm. The sulfur, radiant-dose and NOR selection logic is set out on UV stabilizers for greenhouse and agricultural film, and the carbon-black and oxidative-induction-time requirements for liners sit under additives for geomembranes.

Which UV Stabilizers Are Allowed in Food-Contact and Drinking-Water Plastics?#

A food-contact plastic may contain only UV stabilizers listed in Regulation (EU) No 10/2011, within each substance's specific migration limit, or cleared under 21 CFR 178.2010, within each polymer's weight limit, which excludes 10 of the grades used to make plastics UV resistant, among them Tinuvin 770. The regulation sets an overall migration limit of 10 mg/dm² and a generic specific migration limit of 60 mg/kg, and the migration-limit system behind these numbers is explained on EU 10/2011. Two group restrictions apply: restriction 12 puts the benzotriazoles UV-P (FCM 444), UV-327 (FCM 469) and UV-326 (FCM 470) under one SML(T) of 30 mg/kg, and restriction 8 puts the benzophenones (FCM 317, 318, 319, 359, 431 and 464) under 6 mg/kg.

Table 5. Food-contact and drinking-water status of 10 light-stabilizer grades

US limits are maximum use levels, not recommended dosages; check the food type and condition of use in 21 CFR 178.2010. Cyasorb UV-3346 carries an EU molecular-weight specification that not every commercial grade is confirmed to meet, since Mayzo gives 1,440 to 1,760 g/mol for its equivalent.

Grades on neither list include Tinuvin 770, Tinuvin 292/765, Tinuvin 144, Tinuvin 123, Tinuvin 360, UV-328, UV-329, UV-320, UV-350 and Cyasorb UV-3853, which is why the Tinuvin 791 blend cannot be used for EU plastic food contact: its Tinuvin 770 component is not listed. Food types and conditions of use are decoded on 21 CFR 178.2010.

One benzotriazole is closed to new compounds entirely. UV-328 has been a Stockholm Convention persistent organic pollutant since decision SC-11/11 at COP-11 in May 2023, the first non-halogenated plastic additive listed, and the EU unintentional-trace-contaminant limit under Delegated Regulation (EU) 2025/843 falls from 100 mg/kg on 4 August 2025 to 10 mg/kg on 4 August 2027 and 1 mg/kg on 4 August 2029. The full POP timeline for UV-328 (Tinuvin 328) sits on its substance page. UV-326 and UV-329 have been on the REACH Candidate List as very persistent and very bioaccumulative since 23 January 2024 and appear in ECHA's draft Annex XIV recommendation of 2 February 2026, whose consultation closed on 2 May 2026; neither is on Annex XIV. All eight phenolic benzotriazoles are tracked under benzotriazole UV absorbers: SVHC, Annex XIV and POPs status.

Drinking water runs on a separate instrument. The European positive list under Directive (EU) 2020/2184 includes Chimassorb 944 (entry 0648), Chimassorb 2020 (0687), Tinuvin 622 (0627), Cyasorb UV-3346 (1410), UV-531 (0368) and UV-326 (0406), so a grade can be listed for drinking water and absent from the food-contact Union list, as Tinuvin 770 at entry 0969 is. The US and German rules are compared on plastic additives in drinking-water contact.

Where Do UV-Resistant Compounds and Masterbatch Come From?#

UV-resistant compounds are built from light stabilizers made by BASF (Tinuvin, Chimassorb and Uvinul), Syensqo (Cyasorb), Songwon (SONGSORB), Clariant (Hostavin), Adeka (ADK STAB), Everlight (Eversorb), Mayzo (BLS) and Partinchem (Omnistab), and most of the important chemistries are sold by more than one of them under different names. Plants, brand lines and grades by company are in the directory of UV stabilizer and HALS manufacturers. The market behind those names was worth USD 2.53 billion in 2024 and is forecast at USD 3.72 billion in 2030, a compound annual growth rate of 6.76 % for 2025 to 2030 according to MarketsandMarkets in May 2025, with hindered amines, UV absorbers and quenchers as the three segments. On 21 April 2026 BASF announced a HALS and NOR HALS capacity expansion at Chinaplas, citing Chinese plasticulture demand, without disclosing volumes.

Table 6. Same chemistry, different trade names

Same CAS number, different supplier. Grades with the same chemistry can differ in physical form, particle size and co-additives, so this table is an identification aid and not a drop-in equivalence claim.

Buyers should compare grades by CAS number and food-contact status, not by trade name, because the same chemistry can carry five or more brand names and only the CAS number and the regulatory entry are common to all of them. A plastic additive trade name lookup resolves a brand name to its chemistry, and the additive finder by polymer and function works the other way round.

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What Else Decides Whether a Plastic Survives Outdoors?#

UV resistance is only one of the properties that decide whether a plastic survives outdoors, because surface temperature, water, pollution and chemical contact act on the same part at the same time, and the effect of temperature on photo-oxidation is often greater than the effect of UV dose. A UV cabinet reproduces none of the pollution, biological attack or salt water a real installation meets. The complete route from polymer to grade, class by class, is laid out in UV stabilizer selection on the family hub.

Colour and Surface Temperature#

Colour changes two things at once: a white pigmented part runs 10 to 15 °C cooler at the surface than a black one outdoors, while black carbon-filled parts get the best UV screening available, so the choice trades surface temperature against UV absorption. Rutile titanium dioxide offers the middle route, screening UV and giving opacity in the same pigment. Pigment choice is covered in full under colorants for plastics, including the interactions that change a light-stabilizer dosage.

Carbon black carries one cost that has nothing to do with weathering. It absorbs in the near infrared as well as the UV, so black packaging cannot be sorted by near-infrared detection at a recycling plant, which makes a black UV-stabilized part a design for recycling problem rather than a durability one.

Heat, Water and Chemicals Alongside UV#

Heat, water and chemicals decide outdoor performance alongside UV: the surface temperature sets the rate of the same oxidation that light starts, humidity hydrolyses the step-growth polymers, and acidic residues deactivate basic hindered amine light stabilizers. Polycarbonate hydrolyses above 70 °C at high humidity, pesticide sulfur residues cut greenhouse film life by 20 to 25 % when they double from about 1,000 to 2,000 ppm, and the acids and bases in a PPS matrix disrupt conventional UV absorbers outright.

Thermal ageing is measured separately, by long-term heat aging in an oven rather than in a UV cabinet, which is why an outdoor specification usually carries both a weathering requirement and a heat-ageing requirement.

Is PEX Pipe UV Resistant?#

PEX is crosslinked polyethylene, so its UV behaviour follows polyethylene: unpigmented PEX is not UV resistant, and the protection comes from the same light stabilizers and carbon black used in PE pipe. PEX-a is peroxide-crosslinked at 200 to 250 °C with about 2 % peroxide, and the minimum degree of crosslinking under DIN 16892 is 75 % for PE-Xa, 65 % for PE-Xb and 60 % for PE-Xc and PE-Xd, with ASTM F876 asking 65 to 89 %, none of which changes the photo-oxidation route. Carbon black, antioxidant and oxidative-induction-time requirements for every pipe material are on additives for plastic pipes.

Is UV Resistant the Same as Weather Resistant?#

No: UV resistance covers only the light part of weathering, while weather resistance also takes in heat, moisture cycling, freeze-thaw, pollution, biological attack and salt, none of which a UV cabinet reproduces. The weathering practices themselves acknowledge the gap by combining light, heat and water in one cycle, which is what ISO 4892-2 and ASTM G154 do. A material that passes a UV exposure has answered one of six questions.

Does UV-Resistant Paint or Clear Coat Work on Plastic?#

UV protection for plastics is compounded into the melt or co-extruded as a cap layer before the part exists, so a coating applied afterwards is a different product class and sits outside the scope of this site. The loadings are not comparable either: a clear coat carries its absorber at 1 to 5 % of a 10 to 80 µm film, while a moulded part carries 0.1 to 0.5 wt% through a wall thousands of times thicker.

What Is UV-Resistant Plastic Sheeting?#

UV-resistant plastic sheeting is polyethylene film that carries a light-stabilizer package, usually an oligomeric hindered amine at 0.1 to 1.0 wt% and, in agricultural film, 0.5 to 2.0 wt% or a NOR grade at 0.2 to 1.6 wt%. The duty classes differ by thickness: mulch film runs 12 to 80 µm, greenhouse film 80 to 220 µm and silage wrap 25 µm in 4 to 6 layers. The non-agricultural grades sit under additives for packaging film. The complete film package, including anti-drip and thermic additives, is on additives for greenhouse film.

Are UV Stabilizers Toxic?#

Most of the oligomeric hindered amines used to make plastics UV resistant, among them Chimassorb 944, Chimassorb 2020, Tinuvin 622, UV-531 and Cyasorb UV-2908, carry no EU harmonised hazard classification, while 3 benzotriazole UV absorbers are regulated for persistence: UV-328 as a Stockholm Convention persistent organic pollutant, and UV-326 and UV-329 as very persistent and very bioaccumulative substances on the REACH Candidate List since 23 January 2024. Two grades do carry harmonised classifications: Chimassorb 119 as Skin Sens. 1 (H317) and Aquatic Chronic 2 (H411) under CLP Annex VI index 613-078-00-1, and Cyasorb UV-3853 as Eye Dam. 1 (H318), Skin Sens. 1 (H317), Aquatic Acute 1 (H400) and Aquatic Chronic 1 (H410). Tinuvin 234 is under ECHA PBT assessment, by a PBT Expert Group written procedure of 5 September 2025, and is not an SVHC. Which light stabilizers appear on the SVHC Candidate List is tracked there.

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