UV Stabilizers for Polypropylene: 5 Stabilizer Classes, Dosage and Selection

UV stabilizers for polypropylene are light-stabilizing additives, mainly hindered amine light stabilizers (HALS) and UV absorbers, that are compounded into PP at 0.05-1.4 wt% to stop sunlight from breaking its polymer chains. PP needs more of them than polyethylene does, because its tertiary carbon atoms make it the most light-sensitive commodity polyolefin, so the question that decides a formulation is which stabilizer suits which PP product.

About 70 % of the world's light stabilizers go into polyolefins, which makes PP and PE the main users of this group of plastic additives. That demand keeps growing: the global UV stabilizer market was worth USD 2.53 billion in 2024 and is forecast to reach USD 3.72 billion by 2030, a CAGR of 6.76 % (MarketsandMarkets, May 2025). Most of that volume protects the same handful of PP product forms: fibres, tapes, film, thick mouldings, automotive TPO and filled compounds, each of which needs a different class and level.

This page covers the mechanism by which sunlight degrades polypropylene, the 5 classes of stabilizer used to stop it, which grade and dosage suit each application from fibres to automotive TPO, how UV stabilizers interact with the rest of the PP additive package, how UV stability is tested by accelerated weathering and outdoor exposure, which grades are listed for food contact and drinking water under EU and US rules, and which producers supply them.

Key figures

• Typical HALS loading in PP: 0.05-1.4 wt%, depending on section thickness and product form
• 5 distinct stabilizer classes are used in PP: HALS, UV absorbers, hindered benzoates, UV screeners and nickel quenchers
• EU specific migration limit for Chimassorb 944 in food-contact PP: 3 mg/kg (FCM 740)
• US maximum use level for Chimassorb 944 in PP: 0.3 wt% (21 CFR 178.2010, CAS 70624-18-9)

Why Does Polypropylene Need UV Stabilizers?#

Polypropylene needs UV stabilizers because 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. Once that bond breaks, the resulting radicals attack the tertiary carbon further down the chain, and the chain undergoes scission rather than crosslinking, so the polymer loses molecular weight and mechanical strength instead of hardening. The hub on UV stabilizers for plastics covers the same 5 classes across every polymer that needs them, from polyethylene to PVC.

How does sunlight degrade polypropylene?#

Sunlight degrades polypropylene through photo-oxidation: PP itself absorbs only below about 250 nm, but hydroperoxides, carbonyl groups and catalyst residues in commercial resin absorb the 290-400 nm sunlight that reaches the ground and start a radical chain reaction. Solar radiation is cut off at the Earth's surface below 280-290 nm by the atmosphere, so pure, defect-free polyolefin would be almost inert to sunlight. Commercial PP is never defect-free: trace hydroperoxides, carbonyl groups, titanium and iron catalyst residues left over from polymerization, and polymer-oxygen charge-transfer complexes all absorb in the 290-400 nm window and act as the initiators that pure PP cannot provide on its own.

The photo-oxidation cycle that follows runs in 4 steps.

1. Alkyl radicals (R•) formed at an initiation site react with atmospheric oxygen to form peroxy radicals (R• + O2 → ROO•).
2. Peroxy radicals (ROO•) abstract a hydrogen atom from a neighbouring tertiary carbon, propagating the chain and forming a hydroperoxide (ROO• + RH → ROOH + R•).
3. Hydroperoxides (ROOH) absorb further UV photons and split into an alkoxy radical and a hydroxyl radical (ROOH + hν → RO• + •OH).
4. Alkoxy radicals (RO•) undergo beta-scission, breaking the main chain and forming a ketone plus a new macroradical that restarts the cycle; the resulting ketones can then undergo Norrish type II scission even at ambient temperature, cutting the chain a second time without further UV input.

Temperature often matters more than UV dose in this cycle, because the propagation and decomposition steps follow Arrhenius kinetics, so a hot outdoor site degrades PP faster than a cooler one at the same solar dose. The full chemistry of photodegradation of plastics is explained polymer by polymer, including why polyethylene responds differently to the same radical cycle.

What are the signs of UV degradation in polypropylene?#

UV-degraded polypropylene shows 6 typical signs: chalking, surface crazing, gloss loss, colour change, embrittlement and a rising melt flow rate.

• Chalking, a powdery white surface layer formed as degraded polymer erodes away and exposes pigment or filler particles
• Surface crazing, fine cracks that appear as the surface layer shrinks and stiffens faster than the bulk material beneath it
• Gloss loss, a dulling of the surface caused by increasing micro-roughness as chain scission proceeds
• Colour change, measured as yellowness index (YI) or total colour difference (ΔE), from chromophore formation and, in some pigment systems, pigment degradation
• Embrittlement and loss of elongation at break, the mechanical consequence of chain scission reducing molecular weight
• Rising melt flow rate (MFR), the processing-side signature of the same chain scission, since shorter chains flow more easily under the same load

Is polypropylene UV resistant?#

No: unstabilized polypropylene is not UV resistant, and it becomes suitable for outdoor use only when HALS, UV absorbers or a UV-screening pigment such as carbon black are compounded into it. PP's tertiary C-H bonds make it more light-sensitive than polyethylene or most other commodity plastics, so the property is added by formulation, not inherited from the base resin. Polymers that resist UV without additives are listed under UV-resistant plastics, and PP is not one of them.

What Are the 5 Types of UV Stabilizers for Polypropylene?#

The 5 types of UV stabilizers used in polypropylene are hindered amine light stabilizers (HALS), UV absorbers, hindered benzoates, UV screeners such as carbon black, and nickel quenchers, with HALS carrying most of the protection in PP. They are ordered here by how much of the PP market each class actually protects, from the class used in almost every outdoor PP grade to the class now largely limited to a single application.

1. Hindered amine light stabilizers (HALS)#

HALS are 2,2,6,6-tetramethylpiperidine derivatives that protect polypropylene by trapping the radicals of photo-oxidation and regenerating themselves in the Denisov cycle; they absorb almost no UV light. The piperidine nitrogen is oxidised in service to an aminoxyl (nitroxyl) radical, which traps an alkyl radical (R•) to form an aminoether. That aminoether then reacts with a peroxy radical (ROO•) and regenerates the aminoxyl radical, so a single HALS molecule can scavenge radicals repeatedly rather than being consumed in one event. E.T. Denisov first described this catalytic cycle in Polymer Degradation and Stability 34 (1991) 325-332; Jennifer Hodgson and Michelle Coote at the Australian National University clarified the reaction mechanism computationally in Macromolecules 43 (2010) 4573; and Pieter Gijsman reviewed the accumulated evidence in Polymer Degradation and Stability 145 (2017) 2-10.

That regeneration is what explains why HALS remain effective at loadings as low as 0.05-1 wt%: the same molecule keeps working long after a non-regenerative stabilizer would be exhausted. Their protection is also thickness-independent, because HALS scavenge radicals wherever they sit in the polymer rather than depending on optical path length, which is why they protect thin fibres and the surface of thick mouldings equally well. HALS are, however, less effective than phenolic antioxidants during melt processing itself, so they never replace the primary antioxidant package; they protect the finished part in service, not the melt during extrusion. Grades and basicity data for all hindered amine light stabilizers (HALS) sit on the HALS page, including the full pKb table used to choose a grade for acidic formulations.

Monomeric vs oligomeric HALS in polypropylene#

Monomeric HALS such as Tinuvin 770 (480.7 g/mol) move quickly to the surface of thick PP parts, while oligomeric HALS such as Chimassorb 944 (Mn 2,000-3,100 g/mol) stay in thin fibres, tapes and films without evaporating or washing out. Low-molecular-weight HALS diffuse fast enough to replenish the outer, most heavily attacked layer of a thick moulding, but that same mobility makes them more volatile and more easily extracted from thin sections, so they are a poor choice for fibres or film. Oligomeric HALS resist extraction because their higher molecular weight slows diffusion, which suits thin, high-surface-area products; blends such as Tinuvin 783 (Chimassorb 944 plus Tinuvin 622) and Tinuvin 791 (Chimassorb 944 plus Tinuvin 770) combine the mobility of a monomeric component with the retention of an oligomeric one.

NOR HALS and low-basicity HALS#

NOR HALS and other low-basicity HALS keep working in PP that contains acidic species such as halogenated flame retardants or pesticide residues, because their pKb of about 8-10 is 4-5 units higher than that of basic N-H HALS. Basicity at the piperidine nitrogen governs how easily a HALS is deactivated by acid: an N-H HALS such as Tinuvin 770 (pKb about 4-5) protonates readily and stops working, while an N-alkoxy (NOR) HALS such as Tinuvin 123 or NOR 371 (pKb about 8-10) tolerates the same acidic environment.

Acids that deactivate basic HALS in PP include halogenated flame retardants, sulfur- or halogen-containing pesticide residues carried over in agricultural film, and some acidic pigments; NOR HALS such as Tinuvin NOR 371 are named in supplier literature for these formulations, though its CAS and EC identifiers are not yet established in our source library and are not stated here. NOR HALS are covered in full, with their agricultural-film uses.

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

UV absorbers convert UV photons into harmless heat through an intramolecular proton transfer, and because they follow the Beer-Lambert law, their protection grows with concentration and part thickness. The excited molecule releases the absorbed energy through excited-state intramolecular proton transfer (ESIPT), a mechanism described by J. Crawford in Progress in Polymer Science 24 (1999) 7-43. Because absorption depends on concentration multiplied by optical path length, UV absorbers cannot protect the outer surface of thick parts or thin films at practical loadings the way HALS can; they need enough material in the light path to absorb the incoming photons. Benzotriazole UV absorbers typically absorb across 300-400 nm, while hydroxyphenyl triazines (HPTs) such as Tinuvin 1577 extend down to about 280-350 nm.

In PP, UV absorbers are added to HALS mainly in unpigmented or lightly pigmented parts; they are rarely used alone. Tinuvin 326 is used in PP at 0.1-0.5 wt% together with HALS, and UV-531 at 0.1-0.7 wt%, performing best in films thicker than 100 µm and in thick sections where enough material sits in the optical path. Benzophenone-type UV absorbers generally show lower long-term photo-permanence than benzotriazoles and HPTs, described by BASF as "moderate durability," which is one reason the industry has been moving its portfolio away from the older benzotriazoles UV-328, UV-327, UV-320 and UV-350 toward UV-234, UV-360, HPTs and cyanoacrylate absorbers. All chemical classes of UV absorbers are compared by absorption range and volatility on the UV absorbers page.

3. Hindered benzoates#

Hindered benzoates such as Cyasorb UV-2908 and UV-120 are HALS synergists for thick PP and TPO parts: they scavenge radicals and rearrange under light into benzophenone-type UV absorbers. Suppliers position this class as a synergist rather than a stand-alone stabilizer, added alongside HALS in thick-section PP and TPO to extend service life beyond what HALS alone provides. UV-2908 is used at 0.1-0.5 wt% together with HALS; a specific PP dosage for UV-120 is not established in our source library, so only its US maximum use level is given later in the food-contact matrix.

4. UV screeners: carbon black and titanium dioxide#

Carbon black is the most effective UV screener for polypropylene: it absorbs UV across the solar spectrum in the outer layer of the part, which is why black outdoor PP often needs little or no HALS. Carbon black is the reference UV screen for both polyethylene and polypropylene because it absorbs UV radiation broadly rather than at a narrow wavelength band, blocking it from reaching the polymer beneath the pigmented surface layer. Rutile titanium dioxide and zinc oxide also absorb and scatter UV; W. Brostow, X. Lu, O. Gencel and A.T. Osmanson at the University of North Texas (LAPOM), in Materials 13 (2020) 1626, showed that nano-ZnO gave strong UV resistance when compounded into PP films alongside HALS, using a laboratory UV dose 121 times the outdoor solar dose measured in Texas.

Not every pigment helps. Copper phthalocyanine pigments can act as photoinitiators rather than protectants, so pigment choice and HALS interaction need checking together in any coloured outdoor grade. Grades and particle sizes for the screener class are on carbon black in plastics, and UV screeners compares TiO2 and ZnO against carbon black in more depth.

5. Nickel quenchers#

Nickel quenchers such as UV-1084 deactivate excited chromophores by energy transfer, but they play only a minor role in PP today and are used mainly in agricultural film. The mechanism takes up energy from excited carbonyl states and singlet oxygen and releases it as heat before that energy can drive further chain scission. UV-1084 (CAS 14516-71-3) falls under the REACH Annex XVII group entry for nickel and its compounds, which is one reason its use has narrowed to legacy agricultural mulch-film formulations rather than expanding into new PP applications.

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

HALS work better than UV absorbers in most polypropylene products because their protection does not depend on thickness, so they protect thin fibres, tapes and the surface of thick parts, while UV absorbers add value mainly in thicker, unpigmented sections. UV absorbers are volatile at processing temperatures to varying degrees: thermogravimetric analysis shows 1 % weight loss at 153 °C for UV-P, 180 °C for UV-326, 183 °C for UV-328, 264 °C for UV-234, 300 °C for Tinuvin 1577 and 333 °C for UV-360, so grade selection has to match the processing window as well as the optical requirement. HALS carry a different limitation: basic N-H grades are deactivated in acidic environments, and oligomeric HALS resist extraction far better than monomeric ones, which is why the table below separates the two classes by 8 practical criteria rather than declaring a single winner.

Some classes simply do not suit certain PP products. Low-permanence or highly volatile UV absorbers are a poor match for hot processing conditions; basic N-H HALS underperform in formulations containing halogenated flame retardants or acidic pesticide residues; and UV-328, now a Stockholm Convention persistent organic pollutant, is excluded from new formulations regardless of its historical performance.

Which UV Stabilizer Is Best for Each Polypropylene Application?#

The best UV stabilizer for polypropylene depends on section thickness, pigmentation and contact with acids or food: oligomeric HALS for fibres, tapes and film, monomeric HALS or HALS blends for thick parts, and HALS plus a benzoate synergist for automotive TPO. The master dosage table below sets out grade, dosage and source for every PP product form covered on this page.

Supplier TDS ranges; trials decide the final level.

Request quotes for HALS and UV absorbers for polypropylene: grade or CAS number, volume, application and country, through the plastic additive supplier finder. Converters comparing grades before an RFQ can also download the AO + HALS Pairing Chart for PP (PDF), available with email, role and company.

PP fibres and nonwovens#

PP fibres and nonwovens use oligomeric HALS at 0.1-1.4 wt%, because thin filaments offer no depth for UV absorbers and low-molecular-weight HALS would evaporate or wash out. The relevant grades are Chimassorb 944, Chimassorb 2020, Tinuvin 622 and blends such as Tinuvin 783 and Tinuvin 111, chosen for extraction resistance during drawing, texturizing and any downstream washing step. Spin-finish and fibre additives are covered under additives for synthetic fibres, which addresses the interaction between HALS and finish oils on the filament surface.

PP tapes, raffia and woven bags#

Woven PP tapes for sacks, FIBC bags and raffia take 0.1-0.8 wt% oligomeric HALS such as Chimassorb 944, Chimassorb 2020 or Tinuvin 783. Mayzo's data for the Chimassorb 944 type widens that range slightly, to 0.2-0.8 wt%, reflecting differences between supplier test protocols rather than a difference in chemistry. Tapes that are water-quenched during extrusion need a HALS grade formulated for low water carry-over, such as Tinuvin XT 55 or Uvinul 5050 H, since the quench bath can otherwise strip out part of the stabilizer before it is fixed in the tape. Chimassorb 944 is the reference oligomeric HALS for tapes and the grade against which most alternatives are benchmarked.

PP film#

PP film uses 0.1-1.0 wt% oligomeric HALS, with a UV absorber such as Tinuvin 326 or UV-531 added when the film is clear or organically pigmented. Tinuvin 783 is used in LLDPE and PP films at the same 0.1-1.0 wt% range, and a benzotriazole UV absorber is added specifically in unpigmented or organically pigmented film, where carbon black cannot provide screening. UV-531 performs best in films thicker than 100 µm, where enough optical path exists for its Beer-Lambert-dependent mechanism to work. Tinuvin 783 combines Chimassorb 944 and Tinuvin 622 in one blend, covering both the extraction resistance and the basicity profile that film applications need.

Thick-section PP mouldings#

Thick PP mouldings such as garden furniture, crates and housings use a mobile monomeric HALS like Tinuvin 770 or a blend such as Tinuvin 791 at 0.1-1.0 wt% to replenish the surface, where UV attack concentrates. Tinuvin 770 is used at 0.1-1.0 wt%, specifically because thick sections need a HALS able to migrate to the surface layer that bears the brunt of solar exposure. Tinuvin 791, a blend of Chimassorb 944 and Tinuvin 770, is used at 0.1-0.8 wt% in garden furniture, bumpers and fascia, while Tinuvin 622 alone covers the same product category at 0.15-0.5 wt% and Chimassorb 944 at 0.05-1.0 wt%. Tinuvin 770 and Tinuvin 791 are not usable in EU food-contact PP, because the Tinuvin 770 component is not listed under Regulation (EU) No 10/2011. Tinuvin 770 protects the surface of thick parts but is not listed for EU food contact, a distinction covered in full in the food-contact section below.

Automotive PP and TPO#

Automotive PP and TPO combine a fatty-ester HALS such as Cyasorb UV-3853 (0.05-0.5 wt%) with a hindered-benzoate synergist such as UV-2908 (0.1-0.5 wt%). Cyasorb UV-3853 is formulated to be compatible with fatty-amide anti-scratch additives commonly used in interior TPO, avoiding the antagonism that some HALS chemistries show against slip agents. Cyasorb UV-3853 carries harmonised classifications for Eye Damage Category 1, Skin Sensitisation Category 1 and Aquatic Acute and Chronic Category 1, which formulators need to account for in the compound's safety data sheet.

Paintable TPO needs a different approach again: a non-interacting HALS such as Tinuvin XT 850 is required, because basic HALS chemistries can interact with acid-cured one-component (1K) automotive paint systems and interfere with cure. The complete interior and exterior package is on additives for automotive plastics, covering flame retardancy, impact modification and scratch resistance alongside UV protection.

Filled, talc-filled and black PP#

Filled and black PP compounds favour Chimassorb 2020, an oligomeric HALS with a narrow molecular-weight distribution that interacts little with pigments and fillers and adds long-term thermal stability. Chimassorb 2020 is used at 0.05-1.0 wt% in these compounds. Talc adsorbs antioxidants from the surrounding polymer, so filled PP formulations need a stronger overall stabilizer package than unfilled grades to compensate for that loss, on top of the UV protection itself. Chimassorb 2020 adds long-term thermal stability in filled PP beyond its UV function, which is one reason it is preferred over lower-molecular-weight alternatives in mineral-filled compounds; fillers for polypropylene sets out the talc and calcium carbonate loadings, typically 20-40 wt% CaCO3, that drive this extra demand.

How Much UV Stabilizer Does Polypropylene Need?#

Polypropylene needs 0.05-1.4 wt% HALS, with the level set by part thickness, pigmentation, the solar dose at the site of use and the required service life. Four factors drive the dosage decision for any given PP product.

• Section thickness, since thin fibres and films need higher percentages to compensate for their small cross-section, while thick mouldings can rely partly on the bulk of material present
• Pigmentation, because carbon black adds its own UV screening and can reduce the HALS level needed, while unpigmented or light-coloured PP needs the full stabilizer package plus, often, a UV absorber
• Solar radiant dose at the installation site, which varies by region and directly scales the rate of photon-driven initiation
• Required service life, since a product specified for 10 years outdoors needs a higher loading than one specified for a single growing season

Annual radiant dose differs sharply by region: Central Europe receives about 100 kilolangleys (kLy) per year, while Saudi Arabia and Egypt receive about 200 kLy per year, roughly double the dose for the same exposure period. FDA use levels published in 21 CFR 178.2010 are legal maxima, not recommended dosages, and the same principle applies to every supplier TDS range on this page: the ranges bracket what has been shown to work, but the exact level for a given specification needs a trial.

Converters most often add HALS as UV masterbatch rather than as neat powder, because masterbatch handles more safely and disperses more evenly at the compounder's let-down ratio. A worked example shows the arithmetic: a 20 wt% HALS masterbatch let down at 2.5 % gives 0.5 wt% HALS in the finished part (0.20 × 2.5 % = 0.5 %). Check the arithmetic for other let-down ratios and masterbatch concentrations in the let-down ratio calculator.

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

UV stabilizers in PP work inside a larger stabilizer package: phenolic antioxidants and phosphites protect the melt, HALS protect the part in service, and thioesters, acidic flame retardants and some pigments can weaken the HALS. Every PP compound carries a base package built around a primary phenolic antioxidant, a phosphite for melt processing, a thioester for long-term heat stability and an acid scavenger such as calcium stearate (up to 1,000 ppm) or hydrotalcite; UV stabilizers are added on top of that package, not in place of it.

Phthalocyanine pigments also nucleate PP, which can cause warpage independent of their photosensitising effect, so their selection touches mechanical design as well as UV stabilization. HALS remain less effective than phenolic antioxidants specifically during melt processing, which is why removing the phenolic package in favour of a higher HALS dose is never a valid substitution. Synergy and antagonism across all additive families are mapped under additive interactions, including the thioester-HALS antagonism referenced above.

How Is the UV Stability of Polypropylene Tested?#

The UV stability of polypropylene is tested by exposing plaques, films or fibres in xenon-arc or fluorescent-UV cabinets, or outdoors, and tracking carbonyl index, melt flow rate, tensile elongation and colour at set intervals. Accelerated laboratory methods compress years of outdoor exposure into weeks, while outdoor exposure racks provide the reference against which those laboratory methods are validated. Cycle details are on accelerated weathering tests, covering both xenon-arc and fluorescent-UV equipment.

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, black standard temperature 65 ± 3 °C, chamber temperature 38 ± 3 °C, relative humidity 50 ± 10 %) is the closest laboratory match to outdoor sunlight for PP.

Laboratory weathering does not simulate every outdoor stress: pollution exposure, biological attack and salt-water contact fall outside every cabinet method listed above, so a laboratory pass does not guarantee identical outdoor performance in a coastal or industrial environment. Brostow, Lu, Gencel and Osmanson used a laboratory UV dose 121 times the solar dose measured in Texas to accelerate their 2020 University of North Texas study, illustrating how far accelerated testing compresses real exposure time.

What to measure: carbonyl index, melt flow rate, tensile and yellowness#

The 4 properties that track UV damage in PP are carbonyl index by FTIR, melt flow rate at 230 °C / 2.16 kg, tensile elongation at break and yellowness index to ASTM E313.

• Carbonyl index, a ratio calculated from FTIR absorbance bands that rises as photo-oxidation forms carbonyl groups along the chain
• Melt flow rate, measured at 230 °C and 2.16 kg per ISO 1133 or ASTM D1238-26, which rises as chain scission shortens the average molecular weight
• Tensile elongation at break, which falls as embrittlement progresses and the chain network can no longer accommodate the same strain
• Yellowness index, measured to ASTM E313-20 (R2025); the older ASTM D1925 method was withdrawn in 1995 and should not appear in a current test report

No numeric pass or fail criterion for these 4 properties in PP is established in our source library; the acceptable end point is set by the individual product specification, not by a universal threshold. How to calculate the carbonyl index from FTIR spectra is explained in full detail elsewhere on this site.

A rising melt flow rate signals chain scission before mechanical failure becomes visible, which makes it one of the earliest warning properties available to a quality laboratory tracking a weathering trial.

Outdoor exposure and radiant dose (kLy)#

Outdoor exposure is rated by radiant dose in kilolangleys (1 kLy = 41.84 MJ/m2), and the same PP part receives about twice the annual dose in Saudi Arabia (about 200 kLy) as in Central Europe (about 100 kLy). One kilolangley equals 1,000 calories per square centimetre, or approximately 11.6 kWh/m2, giving 3 equivalent units for the same quantity of solar energy. Intermediate regions such as Spain, Italy, China and Turkey receive an annual dose of about 120-140 kLy. Temperature still matters more than dose alone in many cases, since the same radiant exposure at a higher ambient temperature drives the autoxidation cycle faster through its Arrhenius-dependent propagation steps.

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

In the EU, food-contact PP may contain only UV stabilizers listed in EU Regulation (EU) No 10/2011, within each substance's specific migration limit; in the US, they must be listed in 21 CFR 178.2010 within each polymer's weight limit, and that excludes common grades such as Tinuvin 770. Neither system uses the word "approved": substances are "listed" under the EU regulation or "cleared" under 21 CFR 178.2010, a distinction this page keeps throughout rather than using the word "approved," which neither authority applies to individual substances.

EU 10/2011 and FDA 21 CFR 178.2010 limits for PP#

Chimassorb 944 illustrates the gap between the two systems: the EU limits its migration to 3 mg/kg of food (FCM 740), while the US caps it at 0.3 wt% of the PP itself (21 CFR 178.2010, listed as CAS 70624-18-9).

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

The EU's generic overall migration limit for any food-contact plastic is 10 mg/dm2 (60 mg/kg for infant formula), which applies alongside any substance-specific SML shown above, and food types and conditions of use for the US column are decoded on 21 CFR 178.2010.

The two systems never map one-to-one: a grade can carry a tight EU migration limit and a loose US weight limit, or the reverse, so a formulation cleared in one jurisdiction still needs checking against the other before export. SML and OML rules are explained in full on EU 10/2011.

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

UV-328 can no longer be used in new PP compounds in the EU: it has been a Stockholm Convention POP 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 a Substance of Very High Concern (SVHC) on 17 December 2014 for PBT and vPvB properties, added to REACH Annex XIV as entry 51 by Regulation (EU) 2020/171 with a sunset date of 27 November 2023, and then listed under the Stockholm Convention's Annex A by decision SC-11/11 at the eleventh Conference of the Parties in May 2023, the first non-halogenated plastic additive to reach that status. The current EU unintentional trace contaminant limits come from Delegated Regulation (EU) 2025/843.

UV-326 and UV-329 sit at an earlier stage of the same regulatory track: both were listed as SVHCs on 23 January 2024 for very persistent, very bioaccumulative (vPvB) properties only, not persistent, bioaccumulative and toxic (PBT), and neither has been added to Annex XIV. ECHA published a draft Annex XIV recommendation covering both substances on 2 February 2026, with the public consultation closing on 2 May 2026, so an authorisation requirement is not yet in force for either grade. UV-326 remains listed for EU food contact under FCM 470 despite its SVHC status, a distinction that will need close tracking if the Annex XIV recommendation advances. UV-328 (Tinuvin 328) carries the full POP timeline, and Tinuvin 326 (UV-326) remains listed for EU food contact despite its SVHC status, which the substance page tracks in detail.

All 8 phenolic benzotriazoles used as plastic UV absorbers are tracked together under benzotriazole UV absorbers: SVHC, Annex XIV and POPs status, which follows each substance's regulatory position as it changes.

Drinking-water contact#

PP parts 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), Chimassorb 2020 (0687) and Tinuvin 622 (0627). The same positive list also carries Cyasorb UV-3346 (entry 1410), Tinuvin 326 (0406), UV-531 (0368), UV-120 (0415), Cyasorb UV-2908 (0632) and Tinuvin 770 (0969), so a substance can appear on the drinking-water list even where, like Tinuvin 770, it is not listed for general food contact under Regulation (EU) No 10/2011. US and German rules for the same use are compared on plastic additives in drinking-water contact.

Who Supplies UV Stabilizers for Polypropylene?#

UV stabilizers for polypropylene come from BASF (Tinuvin and Chimassorb), Syensqo (Cyasorb), Songwon (SONGSORB), Clariant (Hostavin), Adeka (ADK STAB), Everlight (Eversorb) and Mayzo (BLS), and most HALS chemistries are sold by several of them under different names. Partinchem markets equivalent HALS and UV absorbers under its Omnistab range, extending the same chemistries into a wider set of regional supply options. BASF announced a capacity expansion for HALS and NOR HALS production on 21 April 2026, reflecting continued demand growth in the polyolefin stabilizer market.

Trade-name equivalence reflects the same base chemistry; it is not a performance-equivalence claim.

Buyers should compare grades by CAS number and food-contact status, not by trade name, since the same chemistry sold under different brand names can still carry different food-contact listings depending on the country of manufacture and the exact formulation supplied. Plants and grades by company are in the directory of UV stabilizer and HALS manufacturers.

Request quotes for HALS and UV absorbers for polypropylene: grade or CAS, volume, application, country, through the plastic additive supplier finder.

What Other Additives Does Outdoor Polypropylene Need?#

Outdoor polypropylene needs a complete additive package in which UV stabilizers are only one layer, next to antioxidants, an acid scavenger and, depending on the part, nucleating agents, fillers or impact modifiers. The full PP package is on additives for polypropylene, covering every additive class this page references alongside UV stabilization.

Antioxidants for polypropylene#

Every PP 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. Commodity PP grades typically carry less than 400 ppm phenolic antioxidant, a level set primarily to survive melt processing rather than to provide long-term outdoor protection, which is why UV-specific HALS are added on top rather than substituted for it. Dosage by grade is on antioxidants for polypropylene.

UV stabilizers for polyethylene and PVC compared#

Polyethylene uses the same oligomeric HALS as PP at similar levels, whereas PVC needs UV absorbers or NOR HALS because the HCl it releases deactivates conventional HALS. PE differs from PP in one important way: PE crosslinks under UV attack rather than chain-scissioning, so its degradation signature differs even though the same HALS chemistries, at 0.05-0.6 wt% in thick sections and 0.1-1.0 wt% in LDPE or LLDPE film, protect it.

Conventional HALS are largely ineffective in PVC, because the hydrogen chloride released during PVC's own thermal and photo-degradation deactivates basic HALS chemistries almost as fast as they are added; NOR HALS are the practical exception, since their low basicity resists this acid attack. Film and pipe grades are on UV stabilizers for polyethylene.

Why HALS fail in PVC is explained in full detail on UV stabilizers for PVC, including which UV absorber and NOR HALS combinations replace them.

Can UV protection be added to polypropylene after moulding?#

UV stabilizers for polypropylene are compounded into the melt or added as masterbatch before moulding; surface coatings applied afterwards are a paint topic outside the scope of this page. Melt compounding and masterbatch let-down are the 2 practical routes for getting HALS, UV absorbers or a screening pigment into a PP part before it is shaped.

Does black polypropylene resist UV better?#

Yes: carbon black makes black polypropylene considerably more UV resistant than natural or light-coloured PP, because it absorbs UV in the surface layer. That screening effect is why black outdoor PP compounds are often formulated with a lighter HALS package than an equivalent unpigmented grade, though the exact reduction depends on the carbon black grade, loading and part geometry.

How long does polypropylene last in the sun?#

The outdoor life of polypropylene depends on its stabilization, thickness, colour and the local solar dose, so no single figure applies: unstabilized PP degrades fastest, and HALS-stabilized or carbon-black PP lasts many times longer. No specific lifetime figure for PP, stabilized or unstabilized, is established in our source library, so this page does not quote one; site the exposure against the kLy regional doses given above and the weathering test methods described in the testing section to compare formulations under equal conditions.

Are UV stabilizers toxic?#

Most HALS used in polypropylene, 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. Cyasorb UV-3853 is an exception among the HALS covered on this page: it carries harmonised classifications for Eye Damage Category 1 (H318), Skin Sensitisation Category 1 (H317), and Aquatic Acute and Chronic Category 1 (H400, H410). Among the UV absorbers, UV-328 is regulated as a persistent organic pollutant and UV-326 and UV-329 as very persistent, very bioaccumulative substances, classifications that concern environmental persistence rather than acute toxicity to users of the finished PP part.

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