PVC Co-Stabilizers: 6 Types, How They Work and Selection

PVC co-stabilizers are secondary additives, mainly epoxidized oils, polyols, β-diketones, organic phosphites, hydrotalcite and aminouracil, that complete a primary heat stabilizer such as calcium-zinc by scavenging HCl, binding zinc chloride and protecting early colour. Calcium-zinc soaps alone give only moderate long-term stability, so which co-stabilizer fixes which weakness? The stabilizer system as a whole, primary component plus co-stabilizers, makes up 1 to 5% of a PVC formulation, 2 to 4% in typical practice (Ullmann's Encyclopedia of Industrial Chemistry, via ECVM), and within that narrow window the co-stabilizer choice decides whether a compound keeps its colour during extrusion and its strength after years in service.

Calcium-zinc and calcium-organic systems account for 83% of the stabilizers used in EU PVC (VinylPlus, June 2023), and nearly all of them depend on co-stabilizers, the least visible group of plastic additives.

This page covers what a PVC co-stabilizer is and how it differs from a primary stabilizer, why zinc burning forces formulators to add a second line of defence, the 6 chemical classes that do the job (epoxides, polyols, β-diketones, organic phosphites, inorganic HCl scavengers and nitrogen compounds), the 5 stabilization functions behind them, how the choice changes with the primary system (calcium-zinc, barium-zinc, organotin, lead) and with the application (pipe, profile, cable), the dosage levels that are actually sourced versus the legal maxima that are not dosages, how laboratories test the effect, and which grades are listed for food contact in the EU and the US.

Key figures

• 6 chemical classes of PVC co-stabilizer: epoxides, polyols, β-diketones, organic phosphites, inorganic HCl scavengers and nitrogen compounds
• ESBO is used at 1 to 2 wt% as a co-stabilizer, separate from its 25 to 45 wt% role as a main plasticizer
• The FDA caps stearoylbenzoylmethane (SBM) at 0.5 wt% of vinyl chloride homopolymers (21 CFR 178.2010)
• The FDA caps pentaerythritol at 0.4 wt% of rigid PVC (21 CFR 178.2010)

What Is a PVC Co-Stabilizer?#

A PVC co-stabilizer is an additive that has little or no heat-stabilizing power on its own but multiplies the performance of a primary metal or organotin stabilizer, usually by scavenging HCl, binding metal chlorides or substituting labile chlorine atoms. It sits inside the same one-pack as the primary stabilizer and is dosed alongside it, so that the finished stabilizer package, not any single component, covers early colour, long-term stability and processing behaviour together.

The full range of primary PVC heat stabilizers, from calcium-zinc to organotin and lead, is compared on the family hub, where each primary chemistry is set against the co-stabilizers it typically carries.

Primary stabilizer vs co-stabilizer: what is the difference?#

Primary stabilizers such as zinc carboxylates, organotin mercaptides and lead salts carry the heat stabilization of PVC, while co-stabilizers such as ESBO, pentaerythritol and hydrotalcite are added at lower levels to cover the weaknesses of the primary stabilizer. In calcium-zinc chemistry the zinc carboxylate is the fast-acting component: it substitutes labile chlorine atoms and, in doing so, forms zinc chloride (ZnCl2), a strong Lewis acid that eventually attacks the polymer itself. The calcium carboxylate scavenges the released HCl and regenerates the zinc soap in the reaction ZnCl2 + Ca(OOCR)2 to Zn(OOCR)2 + CaCl2, but calcium alone still leaves gaps that co-stabilizers close. Lead chloride, by contrast, is only weakly Lewis-acidic and does not trigger the same runaway reaction, which is one reason lead-stabilized PVC needed fewer co-stabilizers before the EU restriction. Liquid mixed-metal systems based on barium, zinc, calcium, magnesium or potassium carboxylates "require the addition of co-stabilizers, e.g. phosphites" to perform at all, according to stabilizer producer Baerlocher.

Is a co-stabilizer the same as a secondary stabilizer?#

Yes: co-stabilizer, secondary stabilizer, booster and auxiliary heat stabilizer are used as synonyms in the PVC industry, and the variant spellings costabilizer and co-stabiliser appear interchangeably in supplier literature. The one exception is calcium-zinc chemistry, where the calcium carboxylate itself is also called the "secondary stabilizer" because it acts after the zinc carboxylate in the HCl-scavenging cycle. Outside that specific usage, all four terms point to the same class of additive described above.

Why Do PVC Stabilizer Systems Need Co-Stabilizers?#

PVC stabilizer systems need co-stabilizers because no single metal soap both prevents early discoloration and survives long processing: zinc soaps protect colour but generate zinc chloride, and calcium soaps last longer but protect colour poorly. Unstabilized PVC already begins losing HCl above about 70°C, well below typical processing temperatures, and its thermal degradation onset sits near 250°C, compared with about 400°C for polyethylene. Without a co-stabilizer package to intercept that HCl and the reactive species it generates, a calcium-zinc compound cannot hold both performance targets at once.

The zipper mechanism behind PVC thermal degradation starts at allylic and tertiary chlorine defects in the polymer chain, where dehydrochlorination becomes autocatalytic and produces conjugated polyene sequences. Tomaszewska and co-workers (Polymers, 2021) showed that a dehydrochlorination level of only 0.1% already produces unacceptable discoloration, which is why the co-stabilizer package has to act before degradation becomes visible, not after.

Zinc burning and zinc chloride#

Zinc burning is the sudden blackening of zinc-stabilized PVC that occurs when zinc chloride, a strong Lewis acid formed as the zinc soap works, builds up and catalyses runaway dehydrochlorination. Ye and co-workers (2019) describe the same ZnCl2-catalysed zipper mechanism as the trigger for this catastrophic colour failure, which can turn a compound black within minutes once the threshold concentration is reached.

Zinc burning develops in 3 steps.

1. Zinc carboxylate substitutes labile chlorine along the PVC chain and accumulates as zinc chloride (ZnCl2) in the compound.
2. Zinc chloride, a strong Lewis acid, catalyses further zipper dehydrochlorination once its local concentration crosses a threshold.
3. HCl release and polyene growth accelerate together, and the compound blackens suddenly rather than fading gradually.

The zinc soap in most one-packs is zinc stearate, which substitutes labile chlorine and turns into ZnCl2 in the process. Formulators counter zinc burning by adding more calcium carboxylate alongside co-stabilizers such as polyols and β-diketones, which chelate the accumulating zinc chloride or replace the labile chlorine sites before zinc can attack them.

Early colour vs long-term stability#

Early colour and long-term stability are the 2 performance axes of every PVC stabilizer system, and co-stabilizers are chosen to move one without losing the other: β-diketones improve early colour, while polyols and hydrotalcite extend long-term stability. No single co-stabilizer class in the calcium-zinc toolkit optimizes both axes at once, which is why commercial one-packs combine 2 or more classes rather than relying on a single one.

• Early-colour agents: β-diketones (dibenzoylmethane, stearoylbenzoylmethane), which replace labile chlorine sites by zinc-catalysed C-alkylation before they can discolor the melt.
• Long-term-stability agents: polyols (pentaerythritol, dipentaerythritol, THEIC) and hydrotalcite, which chelate or neutralize zinc chloride as it forms and delay the onset of zinc burning.

Other causes of why plastics turn yellow or pink, such as gas fading in polyolefins, are covered separately, since they involve different mechanisms than PVC dehydrochlorination.

What Are the 6 Types of PVC Co-Stabilizers?#

The 6 types of PVC co-stabilizers are epoxides such as ESBO, polyols such as pentaerythritol, β-diketones such as dibenzoylmethane, organic phosphites, inorganic HCl scavengers such as hydrotalcite, and nitrogen compounds such as aminouracil.

1. Epoxides: ESBO and epoxidized linseed oil#

Epoxides are epoxidized vegetable oils and esters whose oxirane rings react with the HCl released by PVC to form chlorohydrins, and ESBO is the standard example, added at 1 to 2 wt% as a co-stabilizer. Zinc and calcium soaps catalyse this ring-opening reaction, which makes epoxides work in synergy with the metal-soap component rather than replacing it. Benaniba, Belhaneche-Bensemra and Gelbard (Polymer Degradation and Stability, 82, 2003, 245) demonstrated the same synergy for epoxidized sunflower oil combined with zinc and calcium stearates.

ESBO (epoxidized soybean oil) carries CAS 8013-07-8, EC 232-391-0, is classed as a UVCB substance and has a molecular weight of about 1,000 g/mol. Czogała and co-workers (2021) place its co-stabilizer dosage at 1 to 2 wt%, far below the 25 to 45 wt% it would need to serve as the main plasticizer of a flexible compound.

Formulators use epoxides across both rigid and flexible PVC, wherever a calcium-zinc or liquid mixed-metal system needs extra HCl-scavenging capacity without adding more metal soap.

Epoxidized linseed oil (CAS 8016-11-3) carries a higher oxirane content than ESBO, which gives it a stronger HCl-scavenging effect at an equivalent dosage, though it is used less widely than ESBO in commercial PVC one-packs.

2. Polyols: pentaerythritol, dipentaerythritol and THEIC#

Polyols are multi-hydroxyl alcohols such as pentaerythritol, dipentaerythritol and THEIC that chelate zinc chloride in calcium-zinc PVC, which delays zinc burning and extends long-term heat stability. Sorbitol and trimethylolpropane also appear in the polyol group, though pentaerythritol is the most widely referenced member in PVC stabilizer literature.

Technical-grade pentaerythritol (CAS 115-77-5, EC 204-104-9, molecular weight 136.15 g/mol) is supplied as roughly 88% mono-pentaerythritol and 12% di-pentaerythritol.

No sourced phr range covers any of the 3 polyols in commercial PVC recipes; suppliers set the dosage in their own technical data sheets. THEIC (tris(2-hydroxyethyl) isocyanurate) is not listed in EU Regulation (EU) No 10/2011, unlike pentaerythritol and dipentaerythritol.

3. β-Diketones: dibenzoylmethane, stearoylbenzoylmethane and acetylacetonates#

β-Diketones such as dibenzoylmethane (DBM) and stearoylbenzoylmethane (SBM) replace labile allylic chlorine atoms in PVC by zinc-catalysed C-alkylation, which gives calcium-zinc compounds very good early colour at low addition levels. A. Michel and co-workers at CNRS Lyon (Polymer Degradation and Stability, 1981, doi 10.1016/0141-3910(81)90003-3) first documented this β-diketone and calcium-zinc synergy, and Minsker, Kolesov and Zaikov (European Polymer Journal, 25, 1989, 1245) extended the mechanistic picture. Calcium and zinc acetylacetonates belong to the same β-diketone group and are used as metal-complexed variants in some formulations.

Dibenzoylmethane (DBM) (CAS 120-46-7, EC 204-398-9, molecular weight 224.25 g/mol) is sold under trade names such as Rhodiastab 83 and Karenzu DK2 and carries a notified H317 skin-sensitiser classification. Stearoylbenzoylmethane (CAS 58446-52-9, EC 261-257-4, molecular weight 386.6 g/mol, trade names Rhodiastab 50 and Karenz DK 1) has the EU food-contact substance number FCM 699.

DBM is not listed in EU Regulation (EU) No 10/2011, so food-contact calcium-zinc systems use SBM (FCM 699) instead. No sourced phr range exists for either DBM or SBM; commercial dosing is set by the one-pack supplier.

4. Organic phosphites: DPDP, TPPi, EHDP and PDDP#

Organic phosphites such as diphenyl isodecyl phosphite (DPDP) and triphenyl phosphite (TPPi) bind zinc chloride, decompose hydroperoxides and can replace labile chlorine, which improves the clarity and colour of flexible and rigid PVC. The chlorine-substitution route runs through an Arbuzov-type reaction, and the same molecules act as secondary phosphite and phosphonite antioxidants in polyolefins, where they decompose hydroperoxides rather than complex metal chlorides.

Phosphorus content figures come from Galata Chemicals' MARKPHOS product data. Triphenyl phosphite has a molecular weight of 310.3 g/mol, an ECHA registration mapping of 1,000 to 10,000 t/y and a typical dosage of up to 3 wt%, the upper bound reported in the ECHA registration mapping rather than a fixed recommendation.

Why is TNPP no longer a recommended PVC phosphite?#

TNPP is no longer a recommended PVC phosphite because it has been on the REACH Candidate List since 16 July 2019 as an endocrine disruptor for the environment when it contains 0.1% or more 4-nonylphenol. The entry was updated on 21 January 2025 to also cover TNPP's intrinsic endocrine-disrupting properties. TNPP (tris(nonylphenyl) phosphite) is not on the REACH Authorisation List (Annex XIV), but its SVHC status is why formulators now favour DPDP, TPPi or PDDP in new PVC one-packs.

5. Inorganic HCl scavengers: hydrotalcite and zeolites#

Hydrotalcite and zeolites are inorganic HCl scavengers: hydrotalcite, a magnesium-aluminium layered double hydroxide, neutralises HCl and exchanges its interlayer carbonate for chloride, while zeolites absorb HCl and sequester zinc chloride. Hydrotalcite follows the general formula [M2+1-xM3+x(OH)2]x+(An-)x/n·mH2O with x between 0.2 and 0.33, idealised as Mg6Al2(OH)16CO3·4H2O. Its PVC effect was first reported in the 1980s and confirmed by van der Ven and co-workers (Applied Clay Science, 17, 2000, 25), and hydrotalcite is now a standard long-term stability component of calcium-zinc systems, sold as ALCAMIZER and the DHT-4 series (Kisuma) or Actilox CAH (Nabaltec). Hydrotalcite is not listed in 21 CFR 178.2010.

Zeolites work by the same 2 mechanisms, HCl absorption and zinc chloride sequestration, according to Gupta, Agarwal and Banerjee (Journal of Vinyl and Additive Technology, 15, 2009, 164). Both hydrotalcite and zeolites appear in cable, pipe and profile compounds wherever a formulation needs to be lead-free.

The same HCl-trapping chemistry makes hydrotalcite one of the main acid scavengers in polyolefins, where it neutralizes catalyst residues rather than dehydrochlorination products.

6. Nitrogen co-stabilizers: aminouracil, dihydropyridine and 2-phenylindole#

Nitrogen co-stabilizers such as 6-amino-1,3-dimethyluracil, 1,4-dihydropyridines and 2-phenylindole replace labile chlorine in PVC by N- or C-alkylation and stop polyene growth without any heavy metal. The N-alkylation mechanism is documented for 6-amino-1,3-dimethyluracil specifically; our source library holds regulatory data rather than a stated mechanism for the other 2 compounds.

6-amino-1,3-dimethyluracil (aminouracil) carries CAS 6642-31-5, EC 229-662-0, a molecular weight of 155.15 g/mol and an EU food-contact SML of 5 mg/kg (FCM 495). Dihydropyridine, the thiodiethanol bis(5-methoxycarbonyl-2,6-dimethyl-1,4-dihydropyridine-3-carboxylate) ester, carries FCM 761 with an SML of 6 mg/kg, and 2-phenylindole carries FCM 383 with an SML of 15 mg/kg. No sourced phr range exists for aminouracil.

Uracil-based chemistry became the core of organic-based stabilizers (OBS) around 1999, when Crompton, now part of Galata Chemicals, introduced it as a heavy-metal-free option for rigid PVC, including food-contact applications.

How Do PVC Co-Stabilizers Work? The 5 Stabilization Functions#

PVC co-stabilizers work through 5 functions described in the Frye-Horst framework: scavenging HCl, substituting labile chlorine, interrupting polyene growth, deactivating Lewis-acidic metal chlorides and acting as antioxidants. A. H. Frye and R. W. Horst set out this framework across 2 papers in the Journal of Polymer Science (40, 1959, 419 to 431, and 45, 1960, 1 to 12), and it still organizes how formulators classify co-stabilizer chemistry today.

1. Scavenge HCl: metal soaps, lead salts, hydrotalcite, zeolite and epoxides neutralize or absorb the HCl released as PVC degrades.
2. Substitute labile chlorines: zinc and cadmium carboxylates esterify these sites, organotin stabilizers form thioethers, and β-diketones and aminouracils alkylate them.
3. Interrupt polyene growth: mercaptans and Diels-Alder reactions with maleates break the conjugated sequences that cause visible discoloration.
4. Deactivate Lewis-acidic metal chlorides: polyols and phosphites complex zinc chloride, and calcium or barium soaps exchange with it directly.
5. Act as antioxidants: phosphites and phenolics decompose hydroperoxides that would otherwise accelerate degradation.

Table: Mechanism matrix by co-stabilizer class

● = main function, ○ = secondary function, blank = not established in our source library for that class.

Download the PVC Stabilizer Selection Guide (PDF) for the full class-by-class comparison in a printable format.

Which Co-Stabilizers Suit Each PVC Stabilizer System and Application?#

The right co-stabilizer depends first on the primary stabilizer: calcium-zinc systems need the full set of co-stabilizers, liquid barium-zinc systems rely on phosphites and epoxides, and organotin systems need the fewest.

Request quotes for PVC co-stabilizers: substance or CAS (ESBO, hydrotalcite, SBM, pentaerythritol, phosphites), volume, stabilizer system, application and country, through the plastic additive supplier finder.

Calcium-zinc and calcium-organic systems#

Calcium-zinc and calcium-organic systems, which make up 83% of EU PVC stabilizer use, combine β-diketones for early colour with polyols, hydrotalcite or zeolite for long-term stability, plus ESBO and phosphites. This combination exists because no single calcium-zinc co-stabilizer covers both performance axes described earlier in this page.

The metal-soap chemistry of calcium-zinc stabilizers is covered in depth on their own page, including the exact soap ratios used across rigid and flexible grades. Where the compound is destined for food contact, formulators choose SBM over DBM because only SBM carries an EU food-contact substance number.

Barium-zinc and liquid mixed-metal stabilizers in flexible PVC#

Liquid barium-zinc and calcium-zinc stabilizers for flexible PVC depend on phosphites and epoxides: the phosphite keeps colour and clarity, while ESBO scavenges HCl and doubles as a secondary plasticizer. Liquid mixed-metal systems replaced cadmium-based stabilizers in semi-rigid and flexible applications, and Reagens documents epoxy co-stabilizers and phosphite boosters as standard components of its plastisol formulations, which gel between 140 and 220°C.

Carrier and phosphite choices for barium-zinc and liquid mixed-metal stabilizers are compared on their own page. DPDP is used as a co-stabilizer in both barium-zinc and calcium-zinc systems, across flexible and rigid PVC alike.

Organotin, lead and OBS systems#

Organotin and lead stabilizers need fewer co-stabilizers than calcium-zinc, because organotin mercaptides substitute labile chlorine themselves and lead chloride does not trigger zinc-type burning. Organotin stabilizers give the best transparency and early colour among PVC stabilizer classes: their mercaptide groups substitute allylic chlorine directly, absorb HCl and release mercaptan that adds across polyene sequences, so much of the co-stabilizer's job is already built into the primary component.

Lead chloride is only weakly Lewis-acidic and delivers very long-term stability, though with poor early colour compared with organotin or calcium-zinc. Lead stabilizers have been restricted in the EU to below 0.1% in PVC since 29 November 2024, under REACH Annex XVII entry 63 (Regulation (EU) 2023/923). Organic-based stabilizer systems built on uracil chemistry offer a heavy-metal-free route for applications that previously used lead or organotin.

Co-stabilizers in PVC pipe, profile and cable compounds#

PVC cable compounds show the co-stabilizer principle most clearly, because calcium-zinc systems need hydrotalcite or zeolite plus polyols to reach the volume resistivity and heat ageing that lead stabilizers once delivered. Cable compounds are classified by temperature rating, at 70, 90, 100/105 and 125°C, according to Reagens technical literature, and each rating demands a correspondingly robust co-stabilizer package.

US and EU pipe systems are compared under stabilizers for PVC pipes, including the methyltin dosage range used in North American practice. Window profile compounds follow a similar calcium-zinc pattern to pipe and cable, with the co-stabilizer package tuned for outdoor weathering rather than electrical performance.

How Much Co-Stabilizer Does a PVC Formulation Contain?#

ESBO is the only PVC co-stabilizer with a sourced general dosage, 1 to 2 wt% when used as a stabilizer, while the whole stabilizer system, primary stabilizer plus co-stabilizers, typically makes up 1 to 5% of a PVC formulation. For most other co-stabilizers, only a single research formulation or a legal maximum is published, not a general commercial range.

Sourced levels exist for ESBO, hydrotalcite (as a single research data point) and TPPi; for SBM and pentaerythritol only legal maxima are published, and those maxima are not recommended dosages. PVC formulations state additive levels in PHR (parts per hundred resin), a ratio to 100 parts of resin rather than a percentage of the finished compound, so a phr value and a wt% value are never interchangeable without converting through the total recipe weight.

Formulators who need to move between the two units can convert a recipe with the PHR to weight percent calculator, which keeps the conversion basis explicit rather than treating phr and wt% as equivalent.

How Is the Effect of a PVC Co-Stabilizer Tested?#

The effect of a PVC co-stabilizer is tested by the Congo red method (ISO 182-1), which times the release of HCl at a laboratory-set temperature, and by static oven ageing, which tracks discoloration of pressed sheets over time. Jiang and co-workers (2020) ran their Congo red test in a 190°C oil bath, while Ye and co-workers (2019) used 180°C with 3 phr of stabilizer, which shows that the test temperature is set by each laboratory rather than fixed by the standard itself.

• Congo red test (ISO 182-1): times how long a PVC sample takes to release enough HCl to turn a Congo red indicator paper, at a temperature the laboratory sets.
• Static oven ageing: tracks the colour of pressed PVC sheets held at a constant temperature, typically 180°C, over an extended period.
• Torque rheometry (ASTM D2538): records fusion behaviour and stability time under shear and heat, rather than colour change alone.

Procedures and endpoints of PVC heat stability testing are described in full on the test page. The 2 main methods measure different endpoints and are not interchangeable: in the Jiang et al. (2020) formulation above, the same compound reached 190 minutes to complete blackening in the static oven test but only up to 46 minutes in the Congo red test, because one method tracks visible colour and the other tracks HCl release.

Which PVC Co-Stabilizers Are Listed for Food Contact?#

In the EU, ESBO, SBM, pentaerythritol, dipentaerythritol, hydrotalcite and aminouracil are listed in Regulation (EU) No 10/2011, while dibenzoylmethane and THEIC are not; in the US, 21 CFR 178.2010 caps SBM at 0.5 wt% and pentaerythritol at 0.4 wt%. The 2 regulatory systems use different mechanisms, migration limits in the EU and use-level caps in the US, so a co-stabilizer's status under one does not predict its status under the other.

EU 10/2011 listings and specific migration limits#

ESBO carries the tightest special rule among the listed co-stabilizers: its general specific migration limit of 60 mg/kg falls to 30 mg/kg for PVC gaskets that seal glass jars of infant formula and baby food. The values below are checked against the 16 March 2025 consolidation of Regulation (EU) No 10/2011, with ESBO and epoxidized linseed oil also checked against the 14 July 2026 consolidation.

Table: Food-contact matrix for PVC co-stabilizers

"Not in our sources" means our sources hold no verified US listing, not that none exists. FDA limits are maximum use levels, not recommended dosages. The Annex II metal limits (barium 1, zinc 5, aluminium 1 mg/kg) apply to the primary stabilizer and to hydrotalcite alike.

OML and SML rules for plastic food-contact materials are explained on EU 10/2011, including the generic overall migration limit of 10 mg/dm2 that applies alongside every substance-specific limit in the table above.

FDA 21 CFR limits for co-stabilizers in vinyl chloride polymers#

The FDA permits stearoylbenzoylmethane at up to 0.5 wt% of vinyl chloride homopolymers and pentaerythritol at up to 0.4 wt% of rigid PVC under 21 CFR 178.2010, while ESBO is covered by a prior sanction in 21 CFR 181.27. These are the only 2 co-stabilizers in this article's scope with a numeric FDA use-level cap; other listed grades, including hydrotalcite and the nitrogen compounds, have no equivalent 21 CFR 178.2010 entry in our source library.

Food types and conditions of use are decoded on 21 CFR 178.2010, the regulation that also authorises the prior-sanctioned stabilizers calcium stearate, zinc orthophosphate and zinc resinate under the adjacent 21 CFR 181.29, the last capped at 50 ppm of migrating zinc.

Perchlorates: listed for rigid PVC, function under verification#

Perchlorates appear in EU Regulation (EU) No 10/2011 with the lowest limit of any PVC co-stabilizer group: 0.002 mg/kg of food, expressed as perchlorate, under group restriction 38, and FCM 1080 is authorised for rigid PVC only. The regulation lists FCM 822, "perchloric acid, salts (perchlorate)" (CAS 14797-73-0), and FCM 1080, "(triethanolamine-perchlorate, sodium salt) dimer", the latter restricted to rigid PVC in food category 01.01.A. Sodium perchlorate itself carries CAS 7601-89-0, EC 231-511-9, and is notified with the hazard statements H271 (oxidizer), H302, H319 and H373. How perchlorates function as a PVC stabilizer booster is not established in our source library, so this page states only their regulatory listing.

Who Supplies PVC Co-Stabilizers?#

PVC co-stabilizers come from specialist producers such as Kisuma (hydrotalcite), Galata Chemicals (MARKPHOS phosphites) and Valtris (epoxidized oils), and most reach PVC processors inside calcium-zinc one-packs from Baerlocher, Reagens or Akdeniz Chemson. Nabaltec supplies hydrotalcite under the Actilox CAH line, and Adeka supplies triphenyl phosphite as ADK STAB TPP. β-Diketones reach the market under trade names such as Rhodiastab 83, Rhodiastab 50, Karenzu DK2 and Karenz DK 1, and organic phosphites under names including Weston TPP, Mark CH 66 and Rostabil TPP, though our source library does not attach a specific manufacturer to each of those trade names. The global PVC stabilizer market was valued at USD 4.6 billion in 2024 and is projected to reach USD 6.9 billion by 2033, according to market research firm IMARC.

One-pack producers are compared in the directory of PVC stabilizer manufacturers, which lists co-stabilizer content alongside the primary chemistry of each product line. Buyers should compare co-stabilizers by CAS number and food-contact listing, not by trade name, since the same trade name occasionally covers more than one chemical composition across suppliers.

Send one request to several producers with the plastic additive supplier finder.

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What Other Additives Work Alongside Co-Stabilizers in PVC?#

Co-stabilizers work inside a PVC formulation that also contains lubricants, processing aids, impact modifiers, fillers, TiO2 and, in flexible grades, plasticizers, and the metal soaps among these interact directly with the stabilizer system. The full formulation is set out on additives for PVC, which covers every required additive family alongside the heat-stabilizer package described on this page.

Metal soaps: calcium stearate and zinc stearate#

Calcium stearate and zinc stearate sit on the border between stabilizer and lubricant: in calcium-zinc PVC they are the primary metal soaps, and calcium stearate also lubricates rigid pipe and profile at 0.4 to 1.5 phr. Calcium stearate (CAS 1592-23-0) is also a prior-sanctioned stabilizer under 21 CFR 181.29, and its lubricant dosage runs from 0.6 to 1.5 phr in rigid pipe and 0.8 to 1.2 phr in profile, according to Struktol technical data sheets, within the broader 0.4 to 1.5 phr range reported by PPI TR-2.

Zinc stearate (CAS 557-05-1) substitutes labile chlorine in calcium-zinc PVC and forms zinc chloride in the process, the same zinc chloride that calcium stearate then helps to neutralize; the zinc component carries an EU Annex II specific migration limit of 5 mg/kg.

The internal-external lubrication balance behind these metal soaps is explained under lubricants for PVC compounding, which sets calcium and zinc stearate against the paraffin and polyethylene waxes used alongside them.

Co-stabilizer chemistry outside PVC#

Three PVC co-stabilizer chemistries, hydrotalcite, polyols and phosphites, also stabilize polyolefins and polyamides, where they do a different job.

Is hydrotalcite used in polyolefins?#

Yes: hydrotalcite is an acid scavenger in PP and PE, where it neutralises catalyst residues in BOPP, BOPE and raffia and protects UV stabilizers in greenhouse film. Hydrotalcite is compared with calcium stearate and zinc oxide under acid scavengers for polyolefins, a role distinct from the HCl-scavenging function it performs in PVC.

Do polyols stabilize nylon?#

Yes: in a 2008 DuPont patent application (US 2010/0029819 A1), 3% dipentaerythritol in glass-fibre-reinforced PA66 kept 99.1% of tensile strength after 500 hours at 210°C, against 78.2% for a copper-only control. This is a single patent example rather than a general performance claim. Copper-halide systems, the more common route to high-heat nylon stabilization, are covered under heat stabilizers for nylon.

Is ESBO a plasticizer or a stabilizer?#

ESBO is both: at 1 to 2 wt% it acts mainly as an HCl-scavenging co-stabilizer, and at 25 to 45 wt% it would serve as the main plasticizer of flexible PVC. Czogała and co-workers (2021) documented both dosage ranges in the same study. ESBO's plasticizer role is covered under epoxidized plasticizers, alongside the other epoxidized oils used at plasticizer-level dosages.

Are PVC co-stabilizers toxic?#

Most PVC co-stabilizers carry low hazard classifications: pentaerythritol is mostly not classified, dibenzoylmethane is notified as a skin sensitiser (H317) and THEIC as an irritant, while sodium perchlorate is an oxidizer and TNPP is an SVHC. These are PubChem-aggregated notifications rather than harmonised CLP classifications, except for TNPP, whose H317, H400 and H410 classification is harmonised under Regulation (EC) No 1272/2008. THEIC carries notified H315, H319 and H335 classifications, and pentaerythritol carries only a single notifier's H412 classification, with most notifiers reporting no classification at all. On the California Proposition 65 list dated 31 July 2026, no co-stabilizer covered on this page is listed.

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