UV Stabilizers for Polyethylene: 4 Stabilizer Classes, Dosage and Selection

UV stabilizers for polyethylene are light-stabilizing additives, mainly hindered amine light stabilizers (HALS), UV absorbers and carbon black, that are compounded into LDPE, LLDPE and HDPE at 0.05-2.0 wt% (carbon black at 2.0-2.5 wt% in pipe) to stop sunlight from embrittling the polymer. Polyethylene is less light-sensitive than polypropylene but still fails outdoors without them, so which stabilizer suits film, agricultural film, tapes, mouldings, tanks and pipe?

About 70% of the world's light stabilizers go into polyolefins, which makes PE and PP the main users of this group of plastic additives, with agricultural film the largest single HALS application in polyethylene. This page compares the four classes that actually protect PE (HALS, UV absorbers, UV screeners and nickel quenchers), shows the recommended grade and dosage for each PE application from packaging film to black pressure pipe, explains how UV stabilizers interact with antioxidants, pigments and pesticide residues, sets out the xenon-arc, fluorescent-UV and outdoor exposure tests used to verify performance, and separates the UV stabilizer grades that are cleared for food-contact and drinking-water PE from those that are not. Suppliers and same-CAS trade-name equivalents close the main content before a short comparison with polypropylene and PVC.

• 0.1-1.0 wt% oligomeric HALS in LDPE and LLDPE packaging film
• 0.5-2.0 wt% HALS in greenhouse, mulch and silage film
• 2.0-2.5 wt% carbon black in PE pressure pipe (EN 12201-1 / ISO 4427-1)
• 0.2 wt% FDA cap for Chimassorb 944 in PE of density 0.94 g/cm3 or more

Why Does Polyethylene Need UV Stabilizers?#

Polyethylene needs UV stabilizers because the hydroperoxides, carbonyl groups and catalyst residues present in every commercial PE grade absorb solar UV and start a radical oxidation that crosslinks and embrittles LDPE, LLDPE and HDPE alike. Polyethylene itself is a poor UV absorber: pure aliphatic polyolefin chains only absorb light below about 250 nm, well short of the 280-290 nm cut-off at which sunlight reaches the ground, so the processing impurities left in the resin do the damage instead. The hub on UV stabilizers for plastics covers the same classes across all polymers, and polypropylene is the more light-sensitive of the two commodity polyolefins because its tertiary carbon-hydrogen bonds oxidize faster than PE's mostly secondary bonds.

Polyethylene grades differ mainly by density, and that density governs how the polymer is used outdoors: LDPE is about 0.924 g/cm3, LLDPE ranges 0.916-0.940 g/cm3, and HDPE is about 0.961 g/cm3. Photo-oxidation attacks all three density classes by the same radical mechanism, but the consequence for the finished part depends on section thickness, colour and the additive package chosen for it.

How does sunlight degrade polyethylene?#

Sunlight degrades polyethylene through photo-oxidation: PE itself absorbs only below about 250 nm, but hydroperoxides, carbonyl groups and catalyst residues in commercial resin absorb the sunlight above 290 nm that reaches the ground and start a radical chain reaction. Titanium and iron catalyst residues left from polymerization, along with polymer-oxygen charge-transfer complexes, act as the initiators that give an otherwise UV-transparent polymer a way to absorb damaging photons.

The photo-oxidation cycle in polyethylene runs in 4 steps. Each step generates the species that drives the next one forward:

1. Alkyl radicals (R•) form at a weak point in the chain and react instantly with atmospheric oxygen to give a peroxy radical, R• + O2 → ROO•.
2. Peroxy radicals (ROO•) abstract hydrogen from a neighbouring chain, ROO• + RH → ROOH + R•, which both propagates the reaction and produces a hydroperoxide.
3. Hydroperoxides (ROOH) absorb UV light and split, ROOH + hv → RO• + •OH, generating two new radicals from every hydroperoxide that breaks down.
4. Alkoxy radicals (RO•) undergo beta-scission of the polymer backbone, forming a ketone and a new macroradical that can start the cycle again.

In PE the macroradicals mainly recombine, so the polymer crosslinks, while ketones formed along the chain split by the Norrish type II reaction. Polyethylene ketones undergo this Norrish type II chain scission at ambient temperature, which means chain breakage and crosslinking proceed side by side in the same degrading part. Temperature often matters more than UV dose for how fast this proceeds, because the reaction follows Arrhenius kinetics rather than a simple photon count. The full chemistry of photodegradation of plastics is explained polymer by polymer.

What are the signs of UV degradation in polyethylene?#

UV-degraded polyethylene shows 6 typical signs: chalking, surface crazing, gloss loss, yellowing, gel formation and embrittlement with a sharp loss of elongation at break. These signs appear roughly in the order given as exposure accumulates:

• Chalking, a powdery white residue on the surface caused by pigment or filler left behind as the surrounding resin erodes
• Surface crazing, fine networks of micro-cracks that form as the outer, most-oxidized layer shrinks against the still-flexible core
• Gloss loss, a dulling of the originally smooth or glossy surface as microscopic roughness develops
• Yellowing, a rise in yellowness index as chromophoric oxidation products accumulate, measurable by FTIR as carbonyl growth
• Gel formation, insoluble crosslinked regions that form as macroradicals recombine across chains
• Embrittlement, a sharp loss of elongation at break that turns a once-flexible film or part brittle enough to crack under normal handling

Is polyethylene UV resistant?#

No: natural (unpigmented) polyethylene is not UV resistant, and LDPE, LLDPE and HDPE become suitable for long outdoor use only when HALS, UV absorbers or a UV screen such as carbon black are compounded into them. Black PE that carries 2.0-2.5 wt% fine carbon black is the exception buyers mean when they call HDPE "UV resistant." Polymers that resist UV without additives are listed under UV-resistant plastics.

What Are the 4 Types of UV Stabilizers for Polyethylene?#

The 4 types of UV stabilizers used in polyethylene are hindered amine light stabilizers (HALS), UV absorbers, UV screeners such as carbon black, and nickel quenchers; HALS carry the protection in natural and coloured PE, carbon black in black pipe and geomembranes. A fifth class, hindered benzoates such as Cyasorb UV-2908, is used as a HALS synergist in thick polypropylene and TPO parts rather than in PE, since our source library carries no PE dosage for that class. The four PE classes are covered in the order of their importance to the polymer, HALS first and nickel quenchers last.

1. Hindered amine light stabilizers (HALS)#

HALS are 2,2,6,6-tetramethylpiperidine derivatives that protect polyethylene by trapping the radicals of photo-oxidation and regenerating themselves in the Denisov cycle; they absorb almost no UV light. In this cycle, first described by E.T. Denisov in Polymer Degradation and Stability 34 (1991) 325-332, the HALS amine is oxidized to an aminoxyl (nitroxyl) radical that traps an alkyl radical to form an aminoether. The aminoether then reacts with a peroxy radical and regenerates the original aminoxyl radical, so a single HALS molecule scavenges many radicals over its service life instead of being consumed once. Jennifer Hodgson and Michelle Coote at the Australian National University clarified the mechanism computationally in Macromolecules 43 (2010) 4573, and Pieter Gijsman reviewed the accumulated evidence in Polymer Degradation and Stability 145 (2017) 2-10.

This regeneration explains HALS efficiency at loadings as low as 0.05-1% and why HALS protection does not depend on part thickness, so the same oligomeric HALS grade protects a 25 micron silage wrap as effectively as the surface of a thick HDPE moulding. HALS are, however, less effective than phenolic antioxidants during melt processing, so they are always used alongside a processing stabilizer rather than in place of one. Grades and basicity data for all hindered amine light stabilizers (HALS) sit on the HALS page.

Monomeric vs oligomeric HALS in polyethylene#

Oligomeric HALS such as Chimassorb 944 (Mn 2,000-3,100 g/mol) and Tinuvin 622 (Mn 3,100-4,000 g/mol) are the default in thin PE film and tapes because they neither evaporate nor wash out, while monomeric Tinuvin 770 (480.7 g/mol) is reserved for the surface of thick HDPE parts. The molecular weight difference drives this split in use: low-molecular-weight HALS migrate quickly to the part surface and are more volatile and extractable, which suits them to protecting the outer skin of a thick moulding but makes them a poor fit for thin, high-surface-area film.

NOR HALS and low-basicity HALS for agrochemical exposure#

NOR HALS and other low-basicity HALS keep working in PE greenhouse and mulch film that is sprayed with sulfur or halogenated pesticides, because their pKb of about 8-10 is 4-5 units higher than that of basic N-H HALS, which greenhouse film accumulates over a growing season.

BASF reported at the 2010 AMI Agricultural Films conference that raising film sulfur content from about 1,000 to 2,000 ppm cut greenhouse film life by 20-25%, and growing regions such as Spain and Morocco routinely see more than 1,500 ppm sulfur in the film environment. Uvinul 5050 H is a low-basicity oligomeric N-H HALS positioned for exactly this exposure. NOR HALS are compared grade by grade with their pKb values. Tinuvin NOR 371 is named here by dosage only, since our source library does not yet carry a verified CAS number for this grade.

2. UV absorbers (benzophenones, benzotriazoles, triazines)#

UV absorbers convert UV photons into heat through an intramolecular proton transfer, and because they follow the Beer-Lambert law, they protect polyethylene only in proportion to their concentration and the thickness of the part. J. Crawford described this excited-state intramolecular proton transfer (ESIPT) mechanism in Progress in Polymer Science 24 (1999) 7-43. Benzotriazole UV absorbers absorb across 300-400 nm and hydroxyphenyl triazines across 280-350 nm, and because the Beer-Lambert relationship ties their effect to concentration multiplied by path length, a UV absorber that performs well in a thick moulding contributes little in a thin film.

In PE, UV absorbers are added to HALS in unpigmented or organic-pigmented articles and in agricultural film thicker than 100 micron; they are rarely used alone. UV-531 (Chimassorb 81), CAS 1843-05-6, is used in PE thick sections at 0.10-0.5 wt% together with HALS according to BASF, and in LLDPE, LDPE and EVA agricultural film over 100 micron thickness at 0.15-0.5 wt%, with Mayzo's own range for the same grade running 0.1-0.7 wt%. UV-531 (Chimassorb 81) is the benzophenone BASF names for agricultural PE film over 100 micron, though benzophenones carry only moderate long-term photo-permanence by BASF's own description and remain standard in agricultural film chiefly when combined with HALS. Tinuvin 326 is used in PE and EVA at 0.1-0.4 wt% (BASF) or 0.1-0.5 wt% (Mayzo), and Cyasorb UV-1164 (a hydroxyphenyl triazine) is named for agricultural PE as UV-1164L without a numeric dosage figure in our source library.

3. UV screeners: carbon black and titanium dioxide#

Carbon black is the most effective UV screener for polyethylene: at 2.0-2.5 wt% in PE pressure pipe it absorbs UV across the solar spectrum in the outer layer of the part, and finer grades (below 30 nm) protect longer than coarse ones. It works by broadband absorption rather than by radical chemistry, so it protects PE and PP alike regardless of the polymer's own photo-sensitivity, and black cable jacket and black pipe compounds routinely outlast their unpigmented equivalents outdoors as a result.

Particle size drives how long that protection lasts: Ampacet reports that N550 carbon black (40-48 nm primary particle) is sufficient for standard pipe service, while finer grades such as N330 (26-30 nm) or N110 (below 20 nm) are chosen when a pipe or cable jacket must survive more than 3-5 years of direct outdoor exposure. Grades and particle sizes are on carbon black in plastics.

Rutile titanium dioxide and zinc oxide are the other UV screeners used in PE: both absorb and scatter UV light rather than trapping radicals, which makes them useful in white and light-coloured compounds where carbon black cannot be used. TiO2 and ZnO are compared on UV screeners. Copper phthalocyanine pigment, in contrast, can act as a photoinitiator rather than a protectant, so its interaction with the UV package needs checking rather than assuming a benefit.

4. Nickel quenchers#

Nickel quenchers such as UV-1084 deactivate excited chromophores by energy transfer and tolerate agrochemicals, which kept them in PE mulch and greenhouse film, but NOR HALS now take most of that role. UV-1084, CAS 14516-71-3, is a nickel(II) thiobisphenolate that takes up energy from excited states and singlet oxygen and releases it as heat rather than propagating a radical chain. It is not listed in EU Regulation (EU) No 10/2011 Annex I and is covered instead by the REACH Annex XVII group entry for nickel and its compounds. The dossier behind this page describes nickel quenchers as a legacy option whose green tint and nickel content are driving declining use in favour of NOR HALS. Identity and REACH nickel rules are on UV-1084 (nickel quencher).

HALS vs UV Absorbers in Polyethylene: Which Works Better?#

HALS work better than UV absorbers in most polyethylene products because their protection does not depend on thickness, so they protect 12-80 micron mulch film and 25 micron silage wrap as well as the surface of HDPE mouldings, while UV absorbers add value mainly in agricultural film over 100 micron and unpigmented thick parts. The two mechanisms are complementary rather than interchangeable: a UV absorber intercepts photons before they trigger oxidation, but only within the depth its concentration and the Beer-Lambert law allow, while a regenerating HALS keeps scavenging radicals throughout the part regardless of thickness.

Three groups of stabilizer do not suit polyethylene well and are worth naming explicitly. Basic N-H HALS lose effectiveness in film exposed to sulfur or halogenated pesticides, because the acidic residues deactivate the amine site. Volatile UV absorbers are a poor match for hot film extrusion, since thermogravimetric analysis at 1% weight loss ranks UV-P at 153 degrees Celsius, UV-326 at 180 degrees Celsius, UV-328 at 183 degrees Celsius, UV-234 at 264 degrees Celsius, Tinuvin 1577 at 300 degrees Celsius and UV-360 at 333 degrees Celsius, so the lower-volatility grades survive processing best. UV-328 is additionally restricted as a persistent organic pollutant, and hindered benzoates have no PE dosage basis in our source library at all.

Table T1. HALS vs UV absorbers in polyethylene

Which UV Stabilizer Is Best for Each Polyethylene Application?#

The best UV stabilizer for polyethylene depends on thickness, colour, agrochemical exposure and food contact: oligomeric HALS such as Chimassorb 944 or Tinuvin 622 for film and tapes, NOR HALS for pesticide-exposed greenhouse film, and carbon black for pipe and geomembranes. For natural or coloured HDPE, the answer is an oligomeric HALS (Chimassorb 944, Tinuvin 622 or Tinuvin 783) at 0.05-1.0 wt%; for black HDPE it is 2.0-2.5 wt% fine carbon black.

Table T2. Master dosage table for UV stabilizers in polyethylene

Supplier TDS ranges; trials decide the final level. Pipe and geomembrane values are standard requirements, not supplier ranges.

LDPE and LLDPE packaging and industrial film#

LDPE and LLDPE film uses 0.1-1.0 wt% oligomeric HALS such as Chimassorb 944, Chimassorb 2020 or Tinuvin 622, with a UV absorber added when the film is clear or organically pigmented. Tinuvin 783 follows the same 0.1-1.0 wt% range in LLDPE film, and BASF recommends adding a benzotriazole such as UV-326 or a benzophenone such as UV-531 in unpigmented or organic-pigmented film where the polymer itself offers no UV screening. Chimassorb 2020 covers LDPE, LLDPE, EVA and EBA films at the same 0.1-1.0 wt% level, while Uvinul 5050 H is chosen specifically for films that also contain a fluoropolymer processing aid and TiO2.

Slip, antiblock and processing aids that share the film with the UV package are covered under additives for packaging film. Formulators size the HALS level within this range by target service life and handling abrasion, since HALS loss through migration accelerates with mechanical contact.

Greenhouse, mulch and silage film#

Greenhouse, mulch and silage film is the largest HALS application in polyethylene: greenhouse film of 80-220 micron must last 6-45 months, so it takes 0.5-2.0 wt% HALS, or NOR HALS such as Tinuvin NOR 371 at 0.2-1.6 wt% where sulfur or halogenated pesticides are used. Global agricultural film demand reached 2.8 Mt in 2009, according to AMI data cited by renewable-carbon.eu, split between mulch film (45%), greenhouse film (31%) and silage film (24%). Mulch film is thinner and shorter-lived than greenhouse film, running 12-80 micron for a 2-4 month service life, while silage wrap is applied at 25 micron across 4-6 layers.

Uvinul 5050 H at 0.5-2.0 wt% is the standard choice where sulfur exposure is moderate. Where exposure is severe, formulators reach for Tinuvin NOR 371 (0.2-1.6 wt% greenhouse, 0.2-1.0 wt% mulch), Tinuvin XT 200 (0.2-2 wt%), Tinuvin 494 AR (1.0-2.5 wt%) or the blend Tinuvin 111 in mulch film at 0.5-1.5 wt%. Frame contact with wood, iron or aluminium greenhouse structures adds to the pesticide exposure. Syensqo states that its Cyasorb Cynergy A series lasts 4 years or more on greenhouse film and 2 years or more on mulch film under burning-sulfur exposure, a supplier claim rather than an independent test result. Sulfur tolerance, kLy ratings and grade choice are covered in depth under UV stabilizers for greenhouse and agricultural film.

HDPE tapes, raffia and monofilament#

HDPE tapes for woven sacks, raffia and nets take 0.1-0.8 wt% oligomeric HALS such as Chimassorb 944, Chimassorb 2020, Tinuvin 622 or Tinuvin 783, because thin stretched tapes offer no depth for UV absorbers. Chimassorb 944 is the reference oligomeric HALS for HDPE tapes, with Mayzo's own tape range for the same chemistry running 0.2-0.8 wt%; Tinuvin 622 covers the same application at 0.2-0.8 wt%. Since tape and monofilament products rely entirely on radical scavenging rather than UV absorption, extraction resistance during stretching and weaving is the deciding factor between grades.

Thick-section HDPE mouldings and crates#

Thick HDPE mouldings such as crates, bins and outdoor furniture use 0.05-1.0 wt% oligomeric HALS, often topped up with a mobile HALS such as Tinuvin 770 (0.1-0.5 wt%) or a UV absorber such as UV-531 when the part is unpigmented. Chimassorb 944 covers thick HDPE, LLDPE and LDPE sections at 0.05-1.0 wt% (Mayzo's tighter range is 0.05-0.6 wt%), Tinuvin 622 at 0.15-0.5 wt% with a UV absorber recommended in unpigmented articles, and Cyasorb UV-3853 at 0.05-0.5 wt%. Tinuvin 622 combines low basicity with wide food-contact clearance, a common default for thick sections needing regulatory flexibility.

Tinuvin 770 and Cyasorb UV-3853 are not listed in EU Regulation (EU) No 10/2011, so a compounder specifying either for a thick moulding needs to confirm the part is not a food-contact application.

Rotomoulded PE tanks#

Rotomoulded PE tanks need a UV package that also survives the process: more than 80% of rotomoulding material is polyethylene, and 1-2 cycles per hour at about 300 degrees Celsius oven temperature consume antioxidant before the part ever sees sunlight. The internal air temperature typically reaches about 180 degrees Celsius at the process end point, so the antioxidant and UV package has to be sized for processing survival first, sunlight exposure second. Sebastian Aniśko and Mateusz Barczewski, writing in Materials in 2023, measured a carbonyl index above 1.5 in unstabilized bio-based LDPE processed by uniaxial rotomoulding, evidence of how quickly an under-stabilized compound oxidizes in this process. Syensqo markets its Cyasorb Cynergy R-series for rotomoulding with a "UV 20+" rating, a supplier claim whose exact meaning in years or exposure dose is not defined. Powder, antioxidant and cycle-time rules are on additives for rotational molding.

Black PE pipe, cable jackets and geomembranes#

Black PE pipe, cable jackets and HDPE geomembranes rely on carbon black rather than HALS: PE pressure pipe carries 2.0-2.5 wt% carbon black of 10-25 nm under EN 12201-1 and ISO 4427-1, and HDPE geomembranes 2.0-3.0% under GRI-GM13. ISO 4427 requires the carbon black to be introduced as a ready-made pre-compound rather than let down by the extruder from a masterbatch at the machine. Black cable jacket compounds rely on the same screening mechanism, though no specific dosage level for that application is established here.

Carbon black dispersion and OIT rules are on additives for plastic pipes. The full GRI-GM13 property list is on additives for geomembranes. Coloured (blue or yellow) PE pipe uses a colour masterbatch instead, typically at 2-4% let-down.

How Much UV Stabilizer Does Polyethylene Need?#

Polyethylene needs 0.05-1.0 wt% HALS in thick parts, 0.1-1.0 wt% in film and up to 2.0 wt% in agricultural film, or 2.0-2.5 wt% carbon black in black pressure pipe, with the level set by thickness, colour, the solar dose at the site and the required service life. Four factors drive where a formulation lands within these ranges:

• Section thickness, because thinner parts lose more stabilizer to surface migration relative to their volume
• Colour and pigmentation, because carbon black itself contributes UV screening while organic pigments and TiO2 add none
• Agrochemical or industrial exposure, because sulfur, halogens and acidic residues deactivate basic HALS and push the formulation toward NOR HALS
• Required service life, because a 2-4 month mulch film and a 45-month greenhouse film sit at opposite ends of the same dosage range

FDA limits stated in the food-contact section below are legal maxima, not recommended dosages, and should never be read as a target loading.

Most pipe extruders add carbon black as black masterbatch rather than as neat powder, and the arithmetic of let-down ratio decides whether that masterbatch actually clears the 2.0 wt% pipe floor. A standard North American black pipe masterbatch runs 35% carbon black, according to Ampacet, typically let down at 5-6.5% (a 19:1 to 14:1 ratio), giving a finished carbon black content of about 1.75-2.3 wt%. At the low end of that range, 35% masterbatch at 5% let-down works out to 0.35 multiplied by 5%, or 1.75 wt% carbon black, below the 2.0 wt% pipe floor set by EN 12201-1 and ISO 4427-1. A compounder using that masterbatch therefore needs at least 5.7% let-down (2.0 divided by 0.35) to clear the standard. Check the arithmetic in the let-down ratio calculator. Ampacet also cautions against masterbatches loaded above 40% carbon black, since dispersion quality declines beyond that point.

How Do UV Stabilizers Interact with Other Additives in Polyethylene?#

UV stabilizers in PE work inside a larger stabilizer package: phenolic antioxidants and phosphites protect the melt, HALS protect the part in service, and thioesters, pesticide residues, acidic flame retardants and some pigments can weaken the HALS. Irganox 1010, a phenolic antioxidant, is used at 0.05-0.4 wt% in polyolefins, and Irgafos 168, a phosphite processing stabilizer, at 0.05-0.2 wt%, typically at a phosphite-to-phenol ratio between 1:1 and 4:1; neither is replaced by the UV package, since HALS are measurably less effective than phenolics at protecting the polymer during melt processing itself.

Table T3. Co-additive effects on the UV package in polyethylene

Pinking or yellowing of white PE and PP results from over-oxidation of the phenolic antioxidant to coloured quinone compounds, aggravated by low-treated TiO2, NOx gas exposure, high pH from some UV stabilizers, moisture and dark storage. Zinc stearate is the standard remedy, since it forms colourless zinc-quinone complexes that neutralize the discolouration, per Ampacet's formulation guidance. Synergy and antagonism across all families are mapped under additive interactions.

How Is the UV Stability of Polyethylene Tested?#

The UV stability of polyethylene is tested by exposing film, tape or plaque samples in xenon-arc or fluorescent-UV cabinets, or outdoors, and tracking carbonyl index, elongation at break, OIT retention and colour at set intervals. Laboratory tests accelerate the same photo-oxidation chemistry described earlier in the page, while outdoor exposure adds real solar spectrum, temperature cycling and weathering that no cabinet fully reproduces. Cycle details are on accelerated weathering tests.

Accelerated weathering: xenon arc and fluorescent UV#

Xenon-arc testing to ISO 4892-2 (Method A, cycle 1: 102 minutes of light and 18 minutes of water spray at 0.51 W/(m2*nm) at 340 nm) is the closest laboratory match to outdoor sunlight for PE film and mouldings, while HDPE geomembranes follow a fluorescent-UV cycle of 20 hours UV at 75 degrees Celsius and 4 hours condensation at 60 degrees Celsius for 1,600 hours under GRI-GM13.

Table T4. UV weathering test methods and conditions

The xenon-arc standards and the fluorescent-UV standards are not interchangeable methods for the same material class: ASTM D2565, the plastics-specific xenon-arc practice, is explicitly not equivalent to ISO 4892-2, and a result generated under one standard should not be compared directly to a result generated under the other. Laboratory weathering by any of these methods does not simulate pollution, biological attack or salt water, so it remains a screening tool rather than a full substitute for field exposure.

What to measure: carbonyl index, elongation, OIT retention and yellowness#

The 4 properties that track UV damage in PE are carbonyl index by FTIR, elongation at break, oxidative induction time (OIT) retention and yellowness index to ASTM E313. Carbonyl index, calculated as a ratio of infrared absorbance bands, rises as photo-oxidation converts the polymer backbone into ketones, aldehydes and acids, and it is the most direct spectroscopic marker of degradation progress. How to calculate the carbonyl index from FTIR spectra is explained on its own page.

Elongation at break falls sharply once crosslinking and chain scission have accumulated past a threshold, which is why it remains the most direct mechanical indicator of embrittlement even though it changes more abruptly than carbonyl index. Std-OIT and HP-OIT methods are explained under oxidative induction time (OIT); for UV-exposed samples, GRI-GM13 specifies HP-OIT retention of at least 50% after 1,600 hours, and the standard-OIT method is not recommended for UV-exposed samples because its higher test temperature gives unrealistic results for some antioxidant systems. Yellowness index is measured to ASTM E313-20 (R2025); the older ASTM D1925 method was withdrawn in 1995 and should never appear on a current PE weathering report. The only numeric PE pass criterion carried in our source library is the GRI-GM13 geomembrane HP-OIT retention figure; no equivalent film or pipe pass criterion is established here.

Outdoor exposure and radiant dose (kLy)#

Outdoor exposure of PE film is rated by radiant dose in kilolangleys, where 1 kLy equals 41.84 MJ/m2 (about 11.6 kWh/m2), and greenhouse films are specified by the total kLy they withstand against the annual dose at the site. Annual radiant dose varies strongly by latitude and climate, and film suppliers size the UV package against the specific regional figure rather than a single global value. As with UV dose generally, temperature at the installation site often matters as much as the radiant dose itself in determining actual film life.

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

Food-contact polyethylene may contain only UV stabilizers listed in EU Regulation (EU) No 10/2011 (within each substance's specific migration limit) or in US 21 CFR 178.2010 (within a weight limit that depends on PE density), which excludes common grades such as Tinuvin 770 and, in the US, Chimassorb 2020.

EU 10/2011 and FDA 21 CFR 178.2010 limits for PE by density#

Chimassorb 944 shows why PE density matters in the US: 21 CFR 178.2010 caps it at 0.2 wt% in PE of density 0.94 g/cm3 or more and at 0.3 wt% in lower-density PE, while the EU limits its migration to 3 mg/kg of food (FCM 740) whatever the density.

Table T5. Food-contact matrix for polyethylene

FDA limits are maximum use levels, not recommended dosages. Check food type, condition of use and PE density in 21 CFR 178.2010.

SML and OML rules are explained on EU 10/2011. Food types, conditions of use and density classes are decoded on 21 CFR 178.2010.

Restricted benzotriazoles: UV-328, UV-326 and UV-329#

UV-328 can no longer be used in new PE compounds in the EU: it has been a Stockholm Convention persistent organic pollutant since 2023, and the EU limit for it as an unintentional trace contaminant falls from 100 mg/kg (4 August 2025) to 10 mg/kg (2027) and 1 mg/kg (2029). UV-328 was first identified as an SVHC on 17 December 2014 for PBT and vPvB properties, added to REACH Annex XIV as entry 51 by Commission Regulation (EU) 2020/171 with a sunset date of 27 November 2023, and then listed under Stockholm Convention Annex A by decision SC-11/11 at COP-11 in May 2023, the first non-halogenated plastic additive to reach that status. The unintentional trace contaminant limits that follow come from EU Delegated Regulation (EU) 2025/843. UV-328 (Tinuvin 328) carries the full timeline.

UV-326 and UV-329 are a separate case: both were identified as SVHC on 23 January 2024 for very persistent, very bioaccumulative (vPvB) properties only, and neither is on Annex XIV as of this review. Both appear only in ECHA's draft Annex XIV recommendation published 2 February 2026, with the public consultation on that draft closing 2 May 2026. Tinuvin 326 (UV-326) remains listed for EU food contact despite its SVHC status, still carrying FCM 470 and a place on the EU drinking-water positive list at entry 0406. Tinuvin 326 is one of the two UV absorbers BASF names for unpigmented PE thick sections, alongside UV-531, so buyers specifying PE compounds should track its Annex XIV status even though it is not yet restricted. All eight phenolic benzotriazoles are tracked under benzotriazole UV absorbers: SVHC, Annex XIV and POPs status.

Drinking-water pipe#

PE pipes in contact with drinking water in the EU may use UV stabilizers from the European positive list under Directive (EU) 2020/2184, which includes Chimassorb 944 (entry 0648), Tinuvin 622 (0627) and carbon black (0348, at most 2.5% w/w). The same positive list also carries Chimassorb 2020 (entry 0687), Cyasorb UV-3346 (1410, CAS 90751-07-8), Chimassorb 119 (0696), Uvinul 5050 H (0706), Cyasorb UV-1164 (0389) and Tinuvin 326 (0406). Carbon black's drinking-water entry (0348) carries the same benzo(a)pyrene ceiling of 0.25 mg/kg carbon black used in its food-contact clearance. US and German rules are compared on plastic additives in drinking-water contact.

Who Supplies UV Stabilizers for Polyethylene?#

UV stabilizers for polyethylene come from BASF (Tinuvin, Chimassorb and Uvinul), Syensqo (Cyasorb), Songwon (SONGSORB), Clariant (Hostavin), Adeka (ADK STAB), Everlight (Eversorb), Mayzo (BLS) and Partinchem (Omnistab), and most oligomeric HALS are sold by several of them under different names. BASF announced a capacity expansion for HALS and NOR HALS on 21 April 2026 at Chinaplas, driven largely by demand from China's plasticulture (agricultural film) sector.

Table T6. Same-CAS trade names for common PE UV stabilizers (not a performance-equivalence claim)

Buyers should compare grades by CAS number, PE food-contact status and density limit, not by trade name, since the table above shows the same chemistry sold under names that can differ across suppliers and regions. Plants and grades by company are in the directory of UV stabilizer and HALS manufacturers.

What Other Additives Does Outdoor Polyethylene Need?#

Outdoor polyethylene needs a complete additive package in which UV stabilizers are one layer, next to antioxidants and, depending on the product, slip and antiblock agents, antifog agents, processing aids or carbon black. The full PE package is on additives for polyethylene.

Antioxidants for polyethylene#

Every PE compound carries a phenolic antioxidant and a phosphite, typically Irganox 1010 at 0.05-0.4 wt% and Irgafos 168 at 0.05-0.2 wt%, before any UV stabilizer is added. Dosage by grade is on antioxidants for polyethylene.

UV stabilizers for polypropylene and PVC compared#

Polypropylene uses the same oligomeric HALS as PE but at higher levels (up to 1.4 wt% in fibres), whereas PVC needs UV absorbers, TiO2 or NOR HALS because the HCl it releases deactivates conventional HALS. PP is the most light-sensitive of the commodity polyolefins, and automotive PP and TPO parts commonly add a fatty-ester HALS together with a benzoate synergist to meet the higher durability demanded of exterior trim. Fibre, TPO and automotive grades are on UV stabilizers for polypropylene. Buyers searching for a UV stabilizer for automotive or car applications are usually looking for PP or TPO exterior parts rather than PE, since automotive exterior trim is overwhelmingly a polypropylene and TPO application covered on that page.

PVC is a different case entirely: conventional N-H and N-CH3 HALS are largely ineffective there because the hydrogen chloride released during PVC degradation deactivates them, leaving NOR HALS and some low-basicity oligomeric HALS such as Uvinul 5050 H as the practical exceptions. Why HALS fail in PVC is explained on UV stabilizers for PVC.

What does "UV stabilized HDPE" mean on a sheet or product label?#

"UV stabilized HDPE" means that HALS, a UV absorber or carbon black was compounded into the HDPE before the sheet or part was made; it is a property of the compound, not a coating. Surface coatings applied after moulding are a separate technology and are out of scope for this page, which covers only additives compounded into the polymer itself.

Does black polyethylene resist UV better?#

Yes: carbon black makes black polyethylene considerably more UV resistant than natural or white PE, because it absorbs UV in the surface layer; that is why PE pressure pipe carries 2.0-2.5 wt% of it. The same screening effect makes black cable jackets and geomembranes, at their own carbon black levels, the default choice whenever appearance permits it.

How long does polyethylene last in the sun?#

The outdoor life of polyethylene depends on stabilization, thickness, colour and the local solar dose, so no single figure applies: unstabilized natural PE degrades fastest, while stabilized greenhouse film is designed for 6-45 months and mulch film for 2-4 months. Thick, carbon-black-screened or well-stabilized parts achieve longer service lives, but no single verified figure for unstabilized PE service life or accelerated-test toughness loss is established here.

Are UV stabilizers toxic?#

Most HALS used in polyethylene, including Chimassorb 944, Chimassorb 2020 and Tinuvin 622, carry no EU harmonised hazard classification, while some benzotriazole UV absorbers are regulated as very persistent substances. UV-531 and Uvinul 5050 H likewise carry no harmonised classification. Chimassorb 119 is the exception among the common HALS grades, carrying a harmonised classification of Skin Sens. 1 H317 and Aquatic Chronic 2 H411, and Cyasorb UV-3853 carries Eye Dam. 1 H318, Skin Sens. 1 H317, Aquatic Acute 1 H400 and Aquatic Chronic 1 H410. UV-328 is regulated as a persistent organic pollutant rather than through a hazard classification, and UV-326 and UV-329 are regulated for their very persistent, very bioaccumulative (vPvB) properties, not as PBT substances.

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