Calcium-Zinc Stabilizers: How They Work, 5 Co-Stabilizer Classes and Uses in PVC

Calcium-zinc (Ca/Zn) stabilizers are PVC heat stabilizers built on a zinc soap, which replaces unstable chlorine atoms and gives good early colour, and a calcium soap, which absorbs hydrogen chloride and regenerates the zinc soap, boosted by co-stabilizers such as beta-diketones, polyols and hydrotalcite. Together with calcium-organic systems they account for 83% of PVC stabilizer use in the EU (VinylPlus, June 2023), so how does a lead-free soap pair keep PVC from turning black in the extruder?

PVC stabilizers make up 1 to 5% of a PVC formulation (ECVM), a small share by weight among the plastic additives in a compound, yet without them rigid PVC cannot be extruded.

This article covers the composition of a calcium-zinc system, the zinc-calcium exchange mechanism and zinc burning, the 5 co-stabilizer classes that make a commercial Ca/Zn package work, how Ca/Zn compares with lead and organotin stabilizers, its 5 main uses in PVC pipe, profile, cable, flexible film and food packaging, dosage and test methods, its food-contact and REACH status, and the producers that supply it.

Key figures

• 83% of EU PVC stabilizer use is calcium-zinc plus calcium-organic systems (VinylPlus, June 2023)
• 1 to 5% of a PVC formulation by weight is heat stabilizer (ECVM)
• 5 mg/kg is the EU migration limit for zinc from food-contact PVC (Annex II, Regulation (EU) 10/2011)
• <0.1% is the maximum lead content allowed in PVC placed on the EU market since 29 November 2024 (Regulation (EU) 2023/923)

What Are Calcium-Zinc Stabilizers?#

Calcium-zinc stabilizers are mixed-metal soap stabilizer systems for PVC, sold as solid one-packs or liquids, that replaced lead stabilizers in the EU by the end of 2015. They belong to the metal-carboxylate class of PVC heat stabilizers: a zinc carboxylate, usually zinc stearate, paired with a calcium carboxylate, usually calcium stearate, sold as a solid pre-blend, sometimes called a calcium-organic stabiliser (COS) when organic co-stabilizers replace most of the zinc, or as a liquid mixed-metal package. Heat stabilizers of this kind are used almost exclusively in PVC and other chlorinated polymers, since only chlorinated polymers release hydrogen chloride on heating. Calcium-based systems, calcium-zinc and calcium-organic together, took about 50% of global PVC heat stabilizer demand in 2023 against 25.1% for lead and 15.4% for organotin (Wikipedia, citing secondary market data), and the European converting industry completed its voluntary switch from lead by end 2015 under the ESPA and VinylPlus lead-replacement programme.

Calcium-zinc is one of 4 chemical families of PVC heat stabilizers, next to organotin, lead and organic-based systems, and each family solves the same hydrogen-chloride problem with a different chemistry.

What is in a calcium-zinc stabilizer?#

A calcium-zinc stabilizer contains 4 component groups: a calcium soap such as calcium stearate, a zinc soap such as zinc stearate, co-stabilizers such as beta-diketones, polyols and hydrotalcite, and, in one-packs, lubricants. The 4 groups are:

• Calcium soap. Usually calcium stearate; scavenges hydrogen chloride and regenerates the zinc soap, and also acts as an internal PVC lubricant.
• Zinc soap. Usually zinc stearate; substitutes labile chlorine atoms and gives the compound its early colour.
• Co-stabilizers. Beta-diketones, polyols, hydrotalcite or zeolites, epoxidized oils and organic phosphites, controlling zinc chloride and extending long-term stability.
• Lubricants. Internal and external waxes or esters, pre-blended into solid one-packs.

The calcium stearate in a Ca/Zn system carries CAS 1592-23-0 (EC 216-472-8, 607.0 g/mol); its role is set out in Table T1 below.

Table T1. Calcium-zinc building blocks

Zinc stearate supplies the zinc that reacts first with the PVC chain, carrying CAS 557-05-1 (EC 209-151-9, molar mass 632.3 g/mol). Ratios between the calcium soap, the zinc soap and the co-stabilizers are proprietary and set per application by each producer; no single published ratio applies across pipe, profile, cable and film grades, and a Chinese patent recipe found in the SERP (CN106243462A) is a single proprietary formulation, not a general specification.

Solid one-packs vs liquid calcium-zinc stabilizers#

Solid calcium-zinc one-packs combine the stabilizer with lubricants for rigid PVC extrusion and moulding, while liquid calcium-zinc stabilizers carry phosphite co-stabilizers and suit flexible PVC and plastisols. Each solid one-pack is built on a proven stabilizer base, pre-blended with internal and external lubricants for rigid extrusion and injection moulding (Baerlocher, 2019), and supplied as powder, granule, flake, paste or liquid. Liquid mixed-metal systems combine calcium, zinc, barium, magnesium or potassium carboxylates and require added co-stabilizers such as phosphites to remain stable in storage and in the melt (Baerlocher); liquid Ca/Zn and Ba/Zn packages are the systems that replaced cadmium stabilizers in semi-rigid and flexible PVC. Pre-blending itself is covered under one-pack additive systems.

How Do Calcium-Zinc Stabilizers Protect PVC?#

Calcium-zinc stabilizers protect PVC by replacing unstable allylic chlorine atoms, absorbing the hydrogen chloride that PVC releases and neutralising the zinc chloride that this reaction produces. A complete PVC stabilizer system performs 5 functions, a framework first described by Frye and Horst (J. Polym. Sci. 40 (1959) 419 to 431 and 45 (1960) 1 to 12):

1. HCl scavenging, removing hydrogen chloride as it forms
2. Labile-chlorine substitution, replacing reactive allylic and tertiary chlorine atoms before they split off
3. Polyene interruption, breaking the conjugated double-bond sequences that cause discoloration
4. Deactivation of Lewis-acidic metal chlorides, mainly the zinc chloride generated by the zinc soap
5. Antioxidant action, limiting oxidative side reactions during melt processing

Why does PVC need a heat stabilizer?#

PVC needs a heat stabilizer because it starts to lose hydrogen chloride at 100 to 120 °C, well below its melt-processing temperatures, and each lost HCl molecule makes the next one easier to split off. This slow loss accelerates sharply as the polymer approaches 250 °C, the temperature of rapid thermal degradation. The reaction removes chlorine at allylic and tertiary chlorine defects along the chain, a chain reaction known as the zipper mechanism because each elimination activates the neighbouring carbon-chlorine bond (Starnes, College of William and Mary, Prog. Polym. Sci. 27 (2002) 2133). Each step releases another HCl molecule and builds a conjugated polyene sequence, and the polymer's colour shifts from yellow through orange and brown to black as that sequence lengthens.

As little as 0.1% dehydrochlorination already produces unacceptable discoloration in the finished part (Tomaszewska et al., Polymers 13 (2021) 2057). Beyond colour, unmanaged HCl corrodes processing tools, reduces impact strength and lowers the volume resistivity of cable insulation. The zipper chemistry that drives this cascade is explained step by step under PVC thermal degradation.

How do zinc and calcium soaps work together?#

The zinc soap reacts first, swapping unstable chlorine atoms on the PVC chain for stable carboxylate ester groups, and the calcium soap then takes the resulting zinc chloride back into a zinc soap while binding the chloride as harmless calcium chloride. Zinc carboxylate esterifies allylic chlorine sites, a reaction Frye and Horst confirmed with infrared spectroscopy and radiotracer studies (J. Polym. Sci. 40 (1959) 419 and 45 (1960) 1), and this substitution gives Ca/Zn-stabilized PVC its good early colour. The reaction consumes the zinc soap and produces zinc chloride, a strong Lewis acid, as a byproduct.

The calcium soap then regenerates the zinc soap by a ligand-exchange reaction:

ZnCl2 + Ca(OOCR)2 → Zn(OOCR)2 + CaCl2

This exchange was documented by Lévai et al. (1989) and confirmed by Ye et al. (2025); Peter Greven describes the same cycle in its plastics processing literature. Zinc chloride is converted back into active zinc soap while the chloride is bound as calcium chloride, a much weaker Lewis acid. Calcium-zinc systems alone give only moderate long-term stability from this cycle, because the calcium soap eventually depletes, which is why commercial Ca/Zn packages always add co-stabilizers (Michel, Van Hoang and Perrin, CNRS Lyon, Polym. Degrad. Stab. 1981).

What is zinc burning?#

Zinc burning is the sudden blackening of calcium-zinc stabilized PVC that occurs when zinc chloride builds up faster than the calcium soap can convert it, because zinc chloride is a strong Lewis acid that accelerates dehydrochlorination. Once the zinc soap is exhausted, the unconverted zinc chloride catalyses the zipper dehydrochlorination it was meant to prevent, a self-accelerating effect documented by Ye et al. in a study of zinc orotate as a countermeasure (Polymers 11 (2019) 194). The effect appears as a sudden colour collapse rather than a gradual fade. Lead stabilizers do not show this failure mode, because the lead chloride they form is only weakly Lewis-acidic (Nagy, Turcsanyi and Kelen, 1982).

Formulators prevent zinc burning with 4 measures:

• Calcium-to-zinc balance. Keeping enough calcium soap available to convert zinc chloride as it forms.
• Polyols. Chelating zinc chloride directly, before it can catalyse dehydrochlorination.
• Phosphites. Complexing zinc chloride and decomposing hydroperoxides that would otherwise accelerate the cascade.
• Hydrotalcite and beta-diketones. Absorbing hydrogen chloride long term and slowing early colour loss, so less zinc chloride accumulates.

No calcium-to-zinc ratio for commercial one-packs is published in the sources behind this article, so formulators set that balance against their own oven and Congo red data.

What Are the 5 Co-Stabilizer Classes in Calcium-Zinc Systems?#

The 5 co-stabilizer classes in calcium-zinc systems are beta-diketones for early colour, polyols and phosphites that neutralise zinc chloride, hydrotalcite and zeolites that absorb hydrogen chloride over the long term, and epoxidized oils such as ESBO. Each class is compared across all stabilizer families on PVC co-stabilizers, and a sixth, minor group of nitrogen compounds and perchlorate boosters supplements some formulations.

1. Beta-diketones (dibenzoylmethane, stearoylbenzoylmethane)#

Beta-diketones such as dibenzoylmethane (DBM) and stearoylbenzoylmethane (SBM) give calcium-zinc stabilized PVC its white early colour by attaching to unstable chlorine sites in a zinc-catalysed reaction. DBM (CAS 120-46-7, EC 204-398-9) reacts with labile allylic chlorine through zinc-catalysed C-alkylation, a mechanism described by Michel, Van Hoang and Perrin at CNRS Lyon (Polym. Degrad. Stab. 3 (1981), doi 10.1016/0141-3910(81)90003-3) and later reviewed by Minsker, Kolesov and Zaikov (1989); it is sold as Rhodiastab 83 or Karenzu DK2. DBM is not listed in EU Regulation (EU) No 10/2011 Annex I, so food-contact formulators reach instead for its close relative SBM (CAS 58446-52-9), listed as FCM 699 with no migration limit and permitted by the FDA at up to 0.5 wt% of vinyl chloride homopolymers (21 CFR 178.2010); SBM is sold as Rhodiastab 50 or Karenz DK 1. No sourced phr dosage for either substance exists in our source library, so only the FDA figure for SBM, a legal maximum rather than a use level, is stated here.

2. Polyols (pentaerythritol, dipentaerythritol, THEIC)#

Polyols such as pentaerythritol, dipentaerythritol and THEIC extend the long-term stability of calcium-zinc systems by binding zinc chloride before it can trigger zinc burning. Pentaerythritol (CAS 115-77-5) chelates zinc chloride and is capped by the FDA at 0.4 wt% in rigid PVC, counting both free pentaerythritol and its stearate ester (21 CFR 178.2010); the EU lists it as FCM 279 with no specific migration limit. Dipentaerythritol (CAS 126-58-9, FCM 311, no SML) performs the same chelating role at a higher molecular weight. THEIC, tris(2-hydroxyethyl) isocyanurate (CAS 839-90-7), is a third polyol used in Ca/Zn systems, but it is not listed in EU 10/2011 Annex I, so its use must be disclosed wherever a food-contact claim is implied. As with the beta-diketones, no sourced phr dosage exists for any of the three polyols in commercial Ca/Zn formulations.

3. Hydrotalcite and zeolites#

Hydrotalcite, a magnesium-aluminium layered double hydroxide, is the standard long-term component of calcium-zinc systems because it traps hydrogen chloride by exchanging the carbonate between its layers for chloride. Hydrotalcite carries two CAS numbers, 12304-65-3 (EU FCM 604) and 11097-59-9 (EU FCM 592, EC 234-319-3); neither carries a substance-specific migration limit, though the EU Annex II limit for aluminium of 1 mg/kg applies. Its HCl-scavenging effect in PVC was first reported in the 1980s (van der Ven et al., Appl. Clay Sci. 17 (2000) 25), marketed today under brand names such as Kisuma's ALCAMIZER range. In a study by Jiang et al. (Materials 13 (2020) 5223), a formulation of 2.4 phr hydrotalcite plus 0.3 phr zinc stearate plus 0.3 phr zinc acetylacetonate reached 190 minutes to blackening in a 180 °C oven test, but only 46 minutes in the Congo red test, showing that the two methods rank the same system very differently. Hydrotalcite is not listed in 21 CFR 178.2010, and its FDA notification status is not established in the sources behind this article.

Zeolites perform a related function, absorbing HCl and sequestering zinc chloride (Gupta, Agarwal and Banerjee, J. Vinyl Addit. Technol. 15 (2009) 164), and formulators choose between the two by particle size, colour and cost.

4. Epoxidized oils (ESBO)#

Epoxidized soybean oil (ESBO) acts as a second hydrogen chloride trap in calcium-zinc stabilized PVC, typically at 1 to 2 wt%, and softens the compound at the same time. ESBO (CAS 8013-07-8) carries oxirane groups that scavenge HCl by forming chlorohydrins, a reaction catalysed by the same zinc and calcium soaps already in the package (Czogała, 2021; Benaniba, Belhaneche-Bensemra and Gelbard, Polym. Degrad. Stab. 82 (2003) 245, studying epoxidized sunflower oil with zinc and calcium stearates). Functioning as both a co-stabilizer and a secondary plasticizer, ESBO is synergistic with Ca/Zn rather than merely additive. The EU lists it as FCM 532 with a migration limit of 60 mg/kg, reduced to 30 mg/kg for gaskets on infant-formula and baby-food jars (Regulation (EU) No 10/2011).

5. Organic phosphites#

Organic phosphites such as diphenyl isodecyl phosphite (DPDP) and triphenyl phosphite (TPPi) chelate zinc chloride and improve colour and clarity, which is why liquid calcium-zinc stabilizers rely on them. DPDP (CAS 26544-23-0), a liquid phosphite used in both liquid barium-zinc and calcium-zinc packages, carries 8.3% phosphorus (Galata's MARKPHOS range), compared with 7.0% for PDDP, 9.0% for EHDP and 10% for TPPi (CAS 101-02-0). Beyond complexing zinc chloride, organic phosphites decompose hydroperoxides formed during melt processing and can substitute labile chlorine sites through an Arbuzov-type reaction. Neither DPDP nor TPPi is listed in EU Regulation (EU) No 10/2011 Annex I. TNPP, a related phosphite with 4.4% phosphorus, is a REACH Substance of Very High Concern and is not a recommended alternative in any of the phosphite classes used with calcium-zinc systems.

Calcium-organic (COS) systems and boosters#

Calcium-organic (COS) stabilizers replace most or all of the zinc with organic co-stabilizers such as 6-amino-1,3-dimethyluracil, and the EU counts them together with calcium-zinc in its 83% calcium-based share. This uracil-based organic-based stabilizer (OBS) chemistry was introduced by Crompton around 1999; 6-amino-1,3-dimethyluracil (CAS 6642-31-5) is listed as FCM 495 with a 5 mg/kg migration limit and N-alkylates labile chlorine sites much as a beta-diketone does. Sodium perchlorate (CAS 7601-89-0) is marketed as a booster in both Ca/Zn and OBS systems; the EU groups perchlorates under group restriction 38 at a combined limit of 0.002 mg/kg. Uracil chemistry in full, including the organic-based stabilizers (OBS) that eliminate zinc altogether, is covered separately.

Calcium-Zinc vs Lead vs Organotin Stabilizers: How Do They Compare?#

Calcium-based stabilizers are the most used PVC heat stabilizers, with about half of global demand in 2023 and 83% of EU use, but lead still gives the longest heat stability and organotins the best clarity. Calcium-based systems, calcium-zinc and calcium-organic combined, held roughly 50% of the global PVC heat stabilizer market in 2023, ahead of lead at 25.1% and organotin at 15.4% (Wikipedia, citing secondary market data), while VinylPlus reports the calcium-based share of EU use at 83% as of June 2023. Table T2 sets the three families side by side across the criteria that matter most in formulation.

Table T2. Calcium-zinc vs lead vs organotin (qualitative, from named sources)

Qualitative ranking from the sources cited in this article; performance depends on the full formulation.

Methyl-, butyl- and octyltin grades are compared in full on organotin stabilizers.

Lead remains a strong HCl scavenger because the lead chloride it forms is only weakly Lewis-acidic, so lead-stabilized PVC does not burn and reaches very long stability times, with good volume resistivity but poorer early colour than Ca/Zn. Calcium-based dryblends run about 2% lower in density than lead-stabilized dryblends (Baerlocher).

Regionally, calcium-based systems dominate European formulation following the lead-replacement programme completed at the end of 2015 (ESPA/VinylPlus); EU-15 lead stabilizer consumption fell from 127,156 tonnes (2000) to 30,708 tonnes (2010), while calcium-based volumes rose 29,472 tonnes between 2007 and 2014 (ESPA). Where lead stabilizers are still used is covered separately, and North America still runs almost all of its rigid PVC on organotin rather than calcium-based systems (Baerlocher).

What Are the 5 Main Uses of Calcium-Zinc Stabilizers in PVC?#

The 5 main uses of calcium-zinc stabilizers are PVC pipes, window and technical profiles, wire and cable insulation, flexible film, flooring and plastisols, and rigid transparent film for food packaging. Table T3 sets out the Ca/Zn form and co-stabilizers typical of each.

Table T3. Calcium-zinc stabilizer uses by PVC application

Request quotes and TDS/SDS for calcium-zinc stabilizers: application (pipe, profile, cable, film, flooring), form (one-pack powder, flake, liquid), volume, food-contact need, country. Send one request to several Ca/Zn producers with the plastic additive supplier finder. Formulators evaluating a switch can also download the PVC Stabilizer Selection Guide (PDF) by registering their email, role and company.

1. Calcium-zinc stabilizers for PVC pipes#

European PVC pipes, from pressure and sewer pipe to PVC-O and multilayer pipe with recycled cores, run on calcium-zinc or calcium-organic stabilizers, while US pressure pipe still uses 0.3 to 1.0 phr of methyltin. Since the EU lead phase-out, Reagens supplies calcium-based and calcium-organic systems across pressure pipe, sewer pipe, multilayer pipe with recycled cores, cable conduit and molecularly oriented PVC-O. In the United States, methyltin and butyltin mercaptides remain standard, dosed at 0.3 to 1.0 phr under PPI TR-2. In India, pipes and fittings account for roughly 75% of national PVC consumption, and lead-free stabilizer trials ran in the Indian pipe industry in 2016 and 2017 (Platinum Industries, a supplier source); the legal status of any India-specific lead-stabilizer rule is not established in the sources behind this article. Application details specific to pipe are covered under stabilizers for PVC pipes.

2. Calcium-zinc stabilizers for window profiles#

PVC window profiles in Europe use calcium-zinc or calcium-organic one-packs designed for white initial colour, outdoor weathering and low plate-out on the die. Baerlocher positions its calcium-based and calcium-organic one-packs for white, coloured and coextruded window profiles, gutters, roller shutters, sidings and foamed profiles, emphasising accurate initial colour, weathering resistance and low plate-out. In the United States, butyltin stabilizers such as Thermolite 137, which carries 14% tin, remain the standard for siding and window profile. Recycled profile is the main route through which legacy lead still enters the supply chain, under the EU's recovered-rigid-PVC derogation that allows up to 1.5% lead by weight in listed building profiles and sheet until 28 May 2033. Weathering and plate-out targets specific to profile extrusion are set out under stabilizers for PVC window profiles.

3. Calcium-zinc stabilizers for wire and cable#

Calcium-zinc stabilizers replaced lead in European PVC cable insulation, but they reach the required volume resistivity and heat ageing only with hydrotalcite or zeolite and polyol co-stabilizers. Lead was the historical standard for cable because lead chloride does not ionise readily, which keeps the compound's volume resistivity high; calcium-zinc systems match that performance only when hydrotalcite or zeolite and polyol co-stabilizers are added, and Baerlocher describes calcium-based stabilizers as largely used in wires and cables today. PVC cable insulation is qualified across four heat-ageing temperature classes: 70, 90, 100 or 105, and 125 °C (Reagens).

Buyers comparing calcium-zinc against other insulation systems can review the full insulation package under wire and cable compounds, which sets stabilizer choice alongside plasticizer and flame-retardant selection for PVC, LSZH/HFFR and XLPE cable.

4. Flexible PVC: film, flooring and plastisols#

Flexible PVC film, flooring and plastisols use liquid calcium-zinc or barium-zinc stabilizers, and zinc was found in 96% of 151 PVC floorings tested by ETH Zurich in 2024. European flexible PVC film runs almost solely on barium-zinc and calcium-zinc liquid systems (Baerlocher), while flooring and plastisol formulations add potassium-zinc or zinc kickers for foam control, together with epoxy co-stabilizers and phosphite boosters; plastisols themselves gel between 140 and 220 °C during processing (Reagens). In a study of 151 Swiss PVC flooring samples, Wiesinger et al. (ETH Zurich, Environ. Sci. Technol. 58 (2024) 1894) detected zinc in 96% of samples, barium in 72% and tin in 58%, a distribution that reflects the mix of calcium-zinc, barium-zinc and, in older flooring, organotin stabilization in the flexible PVC market. Plasticizer and filler levels for these formulations are set out separately under flexible PVC formulations.

5. Rigid film and food packaging#

Calcium-based stabilizers are the tin-free option for transparent rigid PVC food packaging and shrink film, a segment where organotin mercaptides remain the clarity benchmark. Octyltin, methyltin and estertin mercaptides remain the standard for crystal-clear blister packaging and food film, but Baerlocher positions calcium-based systems as an alternative to tin mercaptides in transparent food packaging and to tin carboxylates in shrinkable PVC film and candy wrap. The EU sets organotin migration limits as tin at 0.18 mg/kg for methyltins, 0.006 mg/kg for di-n-octyltins and 1.2 mg/kg for mono-n-octyltins, against a zinc migration limit of 5 mg/kg for the calcium-zinc alternative. SBM, the food-contact beta-diketone, supports early colour in these formulations at up to 0.5 wt% under FDA rules. Tin and calcium options for blister film are compared in full on heat stabilizers for rigid PVC film.

How Much Calcium-Zinc Stabilizer Does PVC Need?#

PVC compounds contain 1 to 5% heat stabilizer by weight of the formulation (ECVM), and calcium-zinc one-packs sit in this range, with the exact phr set by the application, the processing temperature, the co-stabilizer package and the recycled content. A narrower typical range of 2 to 4% appears in Ullmann's Encyclopedia (via Wikipedia), and ECHA's additive mapping places heat stabilizers at 2 to 3 wt% of the compound. Within the pack, ESBO as a co-stabilizer runs 1 to 2 wt%, and calcium stearate as a lubricant runs 0.6 to 1.5 phr in rigid pipe and 0.8 to 1.2 phr in profile (Struktol data). No sourced phr range exists for commercial Ca/Zn one-packs by application; the supplier's technical data sheet sets the exact level.

Formulators set the total stabilizer level against 4 drivers:

• Application. Pipe, profile and cable each carry a different heat-ageing and electrical specification.
• Processing temperature. Higher melt temperatures accelerate HCl loss and require a higher loading.
• Co-stabilizer package. Hydrotalcite, polyols and phosphites reduce the primary soap loading needed.
• Recycled content. Recovered PVC carries residual degradation products and needs a higher dose.

PVC dosages are given in parts per hundred resin, explained under PHR (parts per hundred resin), rather than weight percent.

As a worked example, a research formulation from Jiang et al. (2020) totalling 3.0 phr of stabilizer in 100 phr of PVC converts by wt% = phr_i / total phr x 100: 3.0 / 103.0 x 100 = 2.91 wt% of the compound before other additives, a calculation based on that research formulation, not a commercial recommendation. Check any recipe with the PHR to weight percent calculator.

How Is the Heat Stability of Calcium-Zinc Stabilized PVC Tested?#

Calcium-zinc stabilized PVC is tested with the Congo red method (ISO 182-1), static oven ageing at about 180 °C and dynamic torque-rheometer runs, which together separate early colour from long-term stability and zinc-burning risk. Table T4 lists what each method measures and under which conditions.

Table T4. Heat stability test methods for calcium-zinc stabilized PVC

In the Jiang et al. (2020) study cited earlier, the same hydrotalcite-stabilized formulation reached 190 minutes to blackening under 180 °C static oven ageing but only 46 minutes under the Congo red test, showing that oven ageing and Congo red separate different failure modes rather than measuring the same thing twice. Thermogravimetric analysis (TGA) is not sensitive enough to detect early-stage PVC degradation, because the mass loss it tracks only becomes measurable well after visible discoloration has already occurred. Procedures for reading and comparing these results in full are detailed under PVC heat stability testing, and colour hold specifically is quantified as yellowness index.

Are Calcium-Zinc Stabilizers Allowed in Food Contact and Lead-Free PVC?#

The calcium and zinc soaps in a Ca/Zn stabilizer are permitted in EU food-contact PVC as salts of stearic acid under Regulation (EU) No 10/2011, with zinc migration limited to 5 mg/kg of food, but each co-stabilizer has its own status. No single "approved" label covers a calcium-zinc package as a whole; every component is checked separately against the EU Union list and, for the US market, against 21 CFR 178.2010.

EU 10/2011 and FDA status of calcium-zinc components#

A food-contact calcium-zinc stabilizer is only as compliant as its least-listed co-stabilizer: stearoylbenzoylmethane is listed in the EU (FCM 699), for example, while dibenzoylmethane and THEIC are not. Table T5 checks each component against the Union list in EU 10/2011 and against the US FDA rules.

Table T5. Food-contact matrix, calcium-zinc components

FDA limits are maximum use levels, not dosages. 21 CFR 181.29 also covers zinc orthophosphate and zinc resinate at a maximum migrant limit of 50 ppm zinc. Always check the specific food type and conditions of use.

Metal stearates carry no dedicated FCM number of their own; both calcium stearate and zinc stearate are covered as salts of the authorised acid stearic acid, FCM 106, under Article 6(3)(a) of Regulation (EU) No 10/2011. Use limits by polymer for the FDA components above are decoded in full on 21 CFR 178.2010: Antioxidants and Stabilizers for Polymers.

Calcium-zinc stabilizers and the EU lead-in-PVC restriction#

Calcium-zinc stabilizers are the main way EU converters meet REACH Annex XVII entry 63, which since 29 November 2024 bans placing PVC articles with 0.1% or more lead on the market. Entry 63, amended by Commission Regulation (EU) 2023/923 of 3 May 2023, prohibits lead at or above 0.1% by weight of the PVC material from that date; articles already on the market before 29 November 2024 remain exempt. Two derogations soften this for recovered material: recovered rigid PVC may contain up to 1.5% lead until 28 May 2033, only in listed building profiles, sheet and multilayer non-drinking-water pipe, with a closed-loop requirement from 28 May 2026 and a mandatory "Contains >= 0.1% lead" marking; the equivalent flexible-PVC derogation ended 28 May 2025 with no lead cap after that date. Cadmium, under entry 23, is capped at 0.01% in PVC.

This restriction formalised what industry had already done voluntarily: the ESPA/VinylPlus lead-replacement programme finished across the EU by end 2015, cutting EU-15 lead stabilizer use from 127,156 tonnes (2000) to 30,708 tonnes (2010) while calcium-based volumes grew 29,472 tonnes between 2007 and 2014. All deadlines and derogations are set out on lead in PVC.

Are calcium-zinc stabilizers non-toxic?#

"Non-toxic" is a sales term, not a classification: the calcium and zinc stearates in Ca/Zn stabilizers are not SVHCs and are unclassified in most notifications, but some notifiers classify zinc stearate as hazardous to aquatic life. Across 3,808 ECHA notifications, calcium stearate was not classified by 85.5% of notifiers, with a minority citing H319 and H335. Zinc stearate was not classified by 61.3% of 2,108 notifications, with a minority citing H400 (aquatic toxicity, 30.9%), H413 and H335. Neither is a REACH SVHC. Dibenzoylmethane carries H317 (skin sensitisation), and no substance in this family other than lead appears on California's Proposition 65 list.

Who Makes Calcium-Zinc Stabilizers?#

Calcium-zinc stabilizers are made by PVC stabilizer specialists such as Baerlocher, Reagens, Galata Chemicals, Valtris and Platinum Industries, and by metal-soap producers such as Peter Greven, while Kisuma supplies the hydrotalcite used in many Ca/Zn systems. Baerlocher supplies calcium-based systems under its BAEROPAN one-pack range, alongside CEASIT calcium stearate and Zincum zinc stearate. Reagens supplies COS calcium-zinc and calcium-organic systems from Italy, Germany, the United States and India. Galata Chemicals supplies mixed-metal stabilizers with its MARKPHOS phosphite range. Valtris supplies heat stabilizers and epoxidized natural oils and opened a new Midland, Michigan office on 17 August 2026. Peter Greven supplies the LIGASTAB CZ preblend, melting at about 100 °C against 120 to 130 °C for the single soaps, alongside its LIGASTAR soaps. Platinum Industries, based in Mumbai and Palghar with a facility in Ain Sokhna, Egypt, supplies Ca/Zn systems under its Highstab brand, and Adeka maintains a dedicated PVC stabilizers segment. The global PVC stabilizer market was estimated at USD 4.6 billion in 2024, forecast by IMARC to reach USD 6.9 billion by 2033.

Plants and product lines are listed in the directory of PVC stabilizer manufacturers. Buyers should compare Ca/Zn one-packs by application, form and food-contact documentation, since formulations are proprietary.

Table T6. Selected calcium-zinc stabilizer producers

Request quotes and TDS/SDS from several producers at once: send one request with the plastic additive supplier finder, specifying application, form, volume, food-contact need and country.

Indian producers of Ca/Zn one-packs, including Platinum Industries, are listed separately under plastic additive manufacturers in India.

What Else Goes into a Calcium-Zinc Stabilized PVC Compound?#

A calcium-zinc stabilized PVC compound also contains lubricants, acrylic processing aids and, depending on the product, impact modifiers, plasticizers, calcium carbonate and titanium dioxide. The complete package is described on additives for PVC, which sets the stabilizer alongside every other additive class a PVC formulator selects.

Lubricants for PVC with calcium-zinc one-packs#

Calcium-zinc one-packs double as lubricant packages, because calcium stearate acts as an internal lubricant in PVC and zinc stearate as an external one. Calcium stearate reduces internal friction between polymer chains, while zinc stearate, melting at about 120 °C (Baerlocher; PubChem gives 130 °C), migrates to the surface and reduces friction against metal tooling. A typical rigid pipe lubricant package combines paraffin wax at 0.6 to 1.5 phr, calcium stearate at 0.6 to 1.5 phr and oxidized polyethylene wax at 0.1 to 0.2 phr (Struktol data), and a Ca/Zn one-pack balances both roles alongside its stabilizing function. The internal/external balance is set out on lubricants for PVC.

Barium-zinc and organic-based alternatives#

Barium-zinc liquids and organic-based stabilizers (OBS) are the two closest alternatives to calcium-zinc: Ba/Zn in flexible PVC, OBS where no heavy metal at all is wanted. Barium-zinc is the main liquid mixed-metal chemistry used in textile coating and flexible film, subject to the EU Annex II barium limit of 1 mg/kg. OBS, built on uracil chemistry, is supplied in three series covering pipe, rigid injection moulding and conduit or profile, and resists torque rise with little stability loss after five reprocessing passes (Plastics Technology, 2005). Liquid systems are covered under barium-zinc and liquid mixed-metal stabilizers.

Can calcium-zinc stabilizers be used in CPVC?#

CPVC is stabilized mostly with methyltin or butyltin systems and dedicated CPVC superpacks, because its 63 to 69% chlorine content and higher processing temperature put a heavier HCl load on the stabilizer. The sources behind this article contain no statement confirming or ruling out calcium-zinc use in CPVC beyond this general picture, so no further claim is made here. Superpacks formulated specifically for CPVC are described under heat stabilizers for CPVC.

How are calcium-zinc stabilizers made?#

Calcium-zinc stabilizers are made by producing calcium and zinc soaps, by precipitation, direct conversion, melt processes or continuous (COAD) processes, and blending them with co-stabilizers and lubricants into powders, granules, flakes, pastes or liquids. Peter Greven's process literature describes these metal-soap production routes, after which the individual soaps are combined with the chosen co-stabilizer package and lubricants and finished into the physical form the application requires.

Can recycled PVC be restabilized with calcium-zinc?#

Recycled PVC is restabilized with fresh stabilizer, and in the EU this typically means calcium-based systems, while legacy lead in recovered rigid PVC is tolerated below 1.5% only in listed building uses until 28 May 2033. This follows from the 83% calcium-based share of EU stabilizer use rather than from a rule specific to recyclate. Wiesinger et al. (2024) found that 16% of 151 Swiss PVC floorings tested contained regulated substances above 0.1 wt%, mainly legacy lead and DEHP carried over from recycled content. Restabilization of recycled PVC is covered alongside the 2023/923 derogation.

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