Calcium Carbonate in Plastics: 4 Grade Types, Loading by Polymer and Selection

Calcium carbonate (CaCO3, CAS 471-34-1) is the highest-volume mineral filler in plastics: a blocky, low-aspect-ratio particle that is compounded into PVC, polypropylene and polyethylene at roughly 5 to 40 wt% to displace resin, raise stiffness and speed up cooling. It comes in four grade types and two entirely different manufacturing routes, so which one belongs in which compound?

Fillers account for about 28% of all plastic additives by weight, and calcium carbonate is the largest single entry in that share. Ceresana put total plastic additive volume at 36.7 Mt in 2023, and fillers alone accounted for more than 19.5 Mt of that figure.

This page works through the four grade types of calcium carbonate filler, how ground calcium carbonate (GCC) differs from precipitated calcium carbonate (PCC), why the mineral is coated with stearic acid and why silane coupling agents fail on it, what the filler does to stiffness, impact strength, density, cost, cycle time and optical properties, how much of it goes into PVC pipe, profile and cable, into polypropylene and into polyethylene film, what goes wrong in processing, how filler content is measured after the fact, its EU and US regulatory status, its effect on recyclability, and who supplies it.

Key figures

• CAS 471-34-1, EC 207-439-9, formula CaCO3, molecular weight 100.09 g/mol
• Density 2.7-2.95 g/cm3, Mohs hardness 3-4, aspect ratio 1-3 (blocky)
• EU food contact: FCM 21, "carbonic acid, salts", Regulation (EU) No 10/2011, no specific migration limit
• Typical loading: 5-40 wt%, depending on the polymer and the product

What Is Calcium Carbonate in Plastics?#

In plastics, calcium carbonate is a mineral filler: a solid, white, chemically inert particle of CaCO3 that is dispersed through the polymer melt at high loading to change cost, stiffness, density and heat transfer rather than chemistry. As a filler it belongs to a broad class of particulate additives, typically loaded at 5 to 70 wt%, that a compounder chooses either as an extender to cut cost or as a functional filler to deliver a property the resin alone cannot. Its place among the other mineral and organic fillers for plastics is set by its low aspect ratio and its price.

Why is calcium carbonate added to plastic?#

Calcium carbonate is added to plastic because it is the cheapest way to take resin out of a part without losing stiffness: the mineral costs a fraction of the polymer it displaces, and it raises modulus, opacity and thermal conductivity at the same time. Six reasons account for most of that use.

• Cost reduction, since the mineral is priced by the tonne and displaces resin volume for volume in the compound
• Stiffness, because a mineral particle raises flexural modulus more than the same weight of unfilled resin
• Opacity and whiteness, since the particle scatters visible light and substitutes in part for white pigment
• Faster cooling, because Omya states that compounds filled with calcium carbonate transfer heat more quickly, increasing production line speed
• Acid scavenging in PVC, because the carbonate reacts with the hydrogen chloride that PVC releases during processing and service
• Pore nucleation in film, because fine ground grades nucleate the micropores that breathable polyethylene film needs

Omya also states that calcium carbonate can replace up to 60% of the polymer in finished articles, a supplier claim rather than an independently measured figure. Polypropylene compounds commonly carry 20 to 40 wt% calcium carbonate for this combination of cost and stiffness, and the USGS names ground and precipitated calcium carbonate among the substitutes for titanium dioxide as a white pigment.

Is calcium carbonate an extender filler or a functional filler?#

Calcium carbonate is both: coarse ground grades in PVC pipe are pure extender fillers that displace resin, while fine and ultrafine grades are functional fillers that nucleate pores in breathable film, scavenge HCl in PVC or toughen polypropylene. An extender filler earns its place on cost alone, and ground calcium carbonate in PVC pipe is the textbook case, added to reduce the resin content of the wall without changing what the pipe does. A functional filler earns its place on a property beyond cost: fine ground calcium carbonate nucleates pores in breathable microporous film during biaxial stretching, coarser and finer grades scavenge the hydrogen chloride that PVC releases during processing, and nano-scale calcium carbonate is listed as a nucleating filler for the polymer matrix itself. Particle size, aspect ratio and oil absorption are compared across all minerals under filler properties.

What Are the 4 Grade Types of Calcium Carbonate Filler?#

The 4 grade types of calcium carbonate filler are uncoated ground calcium carbonate (GCC), stearic-acid-coated GCC, precipitated calcium carbonate (PCC) and ultrafine or nano-PCC, with coated GCC carrying most of the tonnage that goes into plastics. All four are the same substance, CaCO3, reaching the compounder by two different manufacturing routes: mining and grinding for GCC, or chemical precipitation for PCC.

1. Ground calcium carbonate (GCC): limestone, marble and chalk#

Ground calcium carbonate (GCC) is mined limestone, marble or chalk that has been crushed, milled and classified, so its chemistry is set by the deposit and its performance is set by the grinding. Ground limestone also carries the CAS number 1317-65-3 (EC 215-279-6), a separate registry entry from the CaCO3 substance identity (CAS 471-34-1, EC 207-439-9) used for the material once it enters a compound. Across the calcium carbonate range, mean particle size runs from 0.02 to 30 µm, Mohs hardness sits at 3 to 4, density runs 2.7 to 2.95 g/cm3, and the refractive index of calcite is 1.6584 at 589 nm, the value that gives fine GCC its brightening effect in a compound.

Grinding, not the mineral itself, decides how a given GCC grade performs. Because limestone is a naturally occurring mineral that is not chemically modified once it is ground, it carries no REACH registration dossier under Annex V, a status covered in full in the regulatory section below. Our source library holds no separate identity record for a GCC-specific purity, whiteness or median particle size specification, so this page describes the grade type without quoting a single supplier's product spec as if it were generic to all GCC.

2. Stearic-acid-coated GCC#

Stearic-acid-coated GCC is the same mineral with a monolayer of fatty acid grafted onto the particle surface, which is why it is the default grade in rigid PVC profile and in filler masterbatch. The coating chemistry and its effect on dispersion are covered in full below; in outline, the fatty-acid layer makes the particle hydrophobic so it wets into a polyolefin or PVC melt instead of agglomerating. uPVC window profile typically specifies 5 to 15% stearate-coated chalk or marble, a narrower and more consistent band than the uncoated grade sees in less demanding products such as drainpipe.

Coating levels and chemistries for every mineral filler are covered under filler surface treatment.

3. Precipitated calcium carbonate (PCC)#

Precipitated calcium carbonate (PCC) is made by carbonating a lime slurry, which gives control over crystal habit and particle size that grinding cannot match, at a higher price per tonne. The manufacturing routes named in 21 CFR 184.1191, precipitation and carbonation, produce crystal habits described as scalenohedral, rhombohedral or aragonite, a level of shape control no mined mineral can offer. Because PCC is manufactured rather than mined, it does not qualify for the same REACH exemption as ground limestone: it is registered under EC 207-439-9, with 296 active dossiers in a joint submission as of the 2026-09-22 ECHA CHEM check. PCC serves as a fine filler and impact co-modifier in rigid PVC and, as a slurry, in latex gloves.

Identity, crystal habits and the full regulatory matrix for this grade sit on precipitated calcium carbonate (PCC).

4. Ultrafine and nano-PCC grades#

Ultrafine and nano-PCC grades reach median particle sizes below 0.1 µm, which makes them impact co-modifiers and nucleating fillers rather than extenders. Across the full calcium carbonate range, mean particle size reaches down to 0.02 µm, and ultrafine and nano-PCC occupy the bottom of that range, well below the 1 µm level that separates a conventional fine grade from an ultrafine one. Since Regulation (EU) 2018/1881, REACH registrants must describe the nanoforms of a registered substance, a requirement that reaches nano-PCC directly.

A nanoform food-contact clearance for calcium carbonate is not established on this page. FCM 21 covers "carbonic acid, salts" as a group entry without a nanoform specification, and Article 9(2) of Regulation (EU) No 10/2011 allows a nanoform only where it is explicitly authorised and specified in Annex I, so the question of whether a given nano-PCC grade is covered is a compliance check to run against the specific grade, not a blanket clearance.

GCC vs PCC: Which Calcium Carbonate Grade Does a Compound Need?#

Ground calcium carbonate is the right choice wherever the job is to displace resin at the lowest cost, while precipitated calcium carbonate earns its higher price only where a controlled crystal habit or a sub-micron particle is needed, as in rigid PVC impact modification. Both grades share the same chemistry, so the decision is really about process, particle and price rather than substance identity.

Both grades are the same substance, CAS 471-34-1. The difference is process, particle and price, not chemistry.

Why Is Calcium Carbonate Coated with Stearic Acid?#

Calcium carbonate is coated with stearic acid because the bare mineral surface is polar and the polyolefin melt around it is not, so uncoated particles agglomerate, raise viscosity and act as crack initiators instead of as filler. Stearic acid is the standard surface treatment for calcium carbonate, applied as a thin fatty-acid layer that turns a hydrophilic mineral surface hydrophobic.

The effect on melt behaviour is large at high loading. In one peer-reviewed study, an LLDPE masterbatch filled to 60 wt% calcium carbonate showed about 3 times the melt viscosity of the neat polymer; adding 3 wt% wax plus 1.0 wt% zinc stearate brought that viscosity back to just above the neat resin's own level (Journal of Polymer Engineering, DOI 10.1515/polyeng-2022-0133). Stearic acid is the same fatty acid that appears elsewhere in a PVC or polyolefin recipe as an internal lubricant, so a formulator is often already managing its total dose across more than one additive function.

What is the difference between coated and uncoated calcium carbonate?#

Coated calcium carbonate carries a thin stearic-acid layer on each particle and uncoated calcium carbonate does not: the coating makes the filler hydrophobic, so it disperses into a polyolefin or PVC melt at higher loading, with lower viscosity and fewer agglomerates. Window profile formulations specify stearate-coated chalk or marble at 5 to 15% for exactly this dispersion benefit. Oil absorption, the amount of oil a filler surface binds per 100 g, is lower for a coated grade than an uncoated one, because the coating occupies surface sites that would otherwise hold oil or plasticizer; the property is measured to ISO 787-5 or ASTM D281 and read as a proxy for binder demand rather than quoted as a fixed value here, since published figures vary by supplier and grade. The top cut, the d98 particle size, matters more than the median size for both impact strength and film pinholes, coated or uncoated.

Why silane coupling agents do not work on calcium carbonate#

Silane coupling agents are ineffective on calcium carbonate, because the carbonate surface carries none of the reactive hydroxyl groups that silanes need, which is why fatty acids and titanates are used instead. Gelest's technical guide to silane chemistry lists calcium carbonate, alongside chalk, marble, gypsum, barytes, graphite and carbon black, among the substrates on which silane coupling agents perform poorly, because silanes bond through surface silanol or hydroxyl groups that a carbonate mineral does not present.

Titanate coupling agents are the usual substitute for carbonate and sulfate mineral surfaces where a coupling chemistry beyond a plain fatty acid is wanted, alongside zirconate chemistries used less commonly in the same role.

How Does Calcium Carbonate Change the Properties of a Plastic?#

Calcium carbonate changes the physical behaviour of a compound rather than its chemistry: it raises modulus, density, opacity and thermal conductivity, and it lowers cost per kilogram, shrinkage and cycle time. It does not reinforce a plastic in the technical sense, since a low-aspect-ratio particle at 1 to 3 cannot carry load the way a fibre or platelet does; it stiffens the compound instead.

Stiffness: why a blocky filler raises modulus less than talc#

Calcium carbonate raises stiffness less than talc at the same loading because modulus scales with both filler volume fraction and aspect ratio, and a blocky CaCO3 particle has an aspect ratio of 1 to 3 against 5 to 40 for a talc platelet. The Halpin-Tsai equations (Halpin and Kardos, Polymer Engineering and Science 16 (1976) 344-352) model that relationship with a shape factor set at roughly twice the aspect ratio, so a platy filler stiffens a compound far more per unit volume than a blocky one does at the same loading.

Two further models refine that picture for a real compound. The Pukánszky interaction parameter B, from Pukánszky's paper in Composites 21 (1990) 255-262, accounts for the strength of adhesion between filler and matrix rather than shape alone, and the review by Fu, Feng, Lauke and Mai in Composites Part B 39 (2008) 933-961 surveys how particle size, interfacial adhesion and loading level interact across particulate-filled polymers generally. No numeric modulus gain for a CaCO3-filled compound is established on this page; the mechanism and the models that predict it are given here, and a specific gain should be measured on the actual formulation.

Impact strength: how fine coated calcium carbonate toughens polypropylene#

Fine, well-dispersed, stearic-acid-coated calcium carbonate can raise the notched impact strength of polypropylene rather than lower it, because the particles debond from the matrix under load and the thin polymer ligaments between the resulting voids yield instead of cracking. Thio, Argon, Cohen and Weinberg at MIT described this debonding and matrix-ligament-yielding mechanism in Polymer 43 (2002) 3661, and Zuiderduin, Westzaan, Huétink and Gaymans at the University of Twente confirmed it for sub-3 µm coated calcium carbonate in Polymer 44 (2003) 261.

That toughening effect breaks down when the particle size distribution is not controlled. Agglomerates and oversize top-cut particles act as crack initiators instead of debonding sites, which is why the d98 top cut matters more than the median d50 for both impact strength and film pinholes. In rigid PVC, fine PCC works alongside the acrylic and CPE impact modifiers rather than replacing them.

Density, cost per kilogram and cost per litre#

Calcium carbonate is about three times as dense as polypropylene, so every kilogram of resin it replaces buys less volume than the weight saving suggests. At 2.7 to 2.95 g/cm3, calcium carbonate sits well above polyolefins at roughly 0.9 to 0.95 g/cm3 and above PVC at about 1.4 g/cm3.

As a worked example: a PP compound at 30 wt% calcium carbonate (2.7 g/cm3) in a matrix at 0.905 g/cm3 has a compound density of about 1.13 g/cm3, from 1 / (0.30/2.7 + 0.70/0.905). A part made to the same volume as an unfilled part therefore gains about 25% in mass even though the compound costs less per kilogram. Cost per kilogram of a compound is the sum of each ingredient's weight fraction times its price, and cost per litre is that figure multiplied by density, so the saving a filler delivers per unit volume is always smaller than the saving it delivers per kilogram. How the filler is fed and dispersed during compounding is covered under plastic compounding.

Heat transfer and cycle time#

Calcium carbonate conducts heat better than the polymer around it, and Omya states that filled compounds therefore cool faster and run at higher line speeds. No numeric thermal conductivity value for a calcium-carbonate-filled compound is established on this page, so the claim is reported as Omya's own statement rather than as an independently measured figure. Calcium carbonate decomposes rather than melts, with limestone's alpha form listed at a melting point of 825 °C in the Hazardous Substances Data Bank, which makes the mineral thermally stable through every thermoplastic processing window a compounder is likely to use.

Opacity, whiteness and abrasion#

Calcium carbonate adds whiteness and opacity cheaply, which is why the USGS lists ground and precipitated grades among the substitutes for titanium dioxide as a white pigment, but at Mohs 3 it also wears screws, barrels and dies faster than talc does. Calcite's refractive index of 1.6584 at 589 nm gives the mineral its brightening effect, well below titanium dioxide's own refractive index but high enough to raise opacity at high loading. Abrasion scales with Mohs hardness: talc sits at Mohs 1, calcium carbonate at Mohs 3, wollastonite at 4.5, silica at 5.5 to 7 and alumina at 9, so a formulator moving from talc to calcium carbonate should expect faster wear on the same tooling.

How Much Calcium Carbonate Can a Plastic Take? Loading by Polymer#

Plastics take anywhere from about 5 wt% to more than 50 wt% calcium carbonate, with the level set by the polymer, the part's mechanical duty, the particle size and the tolerance for higher density. The table below collects the loading levels established in our source library, each with its basis and grade note, since PVC recipes are written in phr and polyolefin recipes in wt%.

PVC recipes are given in phr (parts per hundred resin) and polyolefin recipes in wt%. To convert, wt% equals the phr of the ingredient divided by the total phr, times 100. Loading figures sourced from encyclopedic references should be confirmed against the supplier's technical data sheet before a recipe is set.

Calcium carbonate in PVC: pipe, window profile and cable#

PVC is the largest consumer of calcium carbonate among all plastics, and the loading splits sharply by product: 15 to 20% in uPVC drainpipe, 5 to 15% of coated chalk or marble in window profile, and up to 70 phr in cable compounds. The Plastics Pipe Institute's TR-2-2023 example pressure-pipe recipe puts a number on the lighter end of that range: PVC resin 100 phr, heat stabilizer 0.70 phr, paraffin wax 1.20 phr, PE wax 0.15 phr, calcium carbonate 5.00 phr, titanium dioxide 0.50 phr, pigment 0.03 phr and calcium stearate 0.45 phr, for a total of 108.03 phr, which converts to 92.57 wt% PVC and 4.63 wt% calcium carbonate. Vinyl siding substrate typically carries about 15% ground limestone, in the same range as drainpipe.

The full PVC filler picture, including calcined kaolin for cable, is on fillers for PVC, and the complete recipe around the filler is set out on additives for PVC. Calcium carbonate also reacts with the hydrogen chloride that PVC releases during processing, which gives it a secondary role as an acid scavenger on top of its role as an extender, and pipe-specific recipes in full are collected under additives for plastic pipes.

Calcium carbonate in polypropylene#

Polypropylene compounds carry calcium carbonate at 20 to 40 wt%, mostly as coated ground grades added through a filler masterbatch, in housewares, thermoformed trays and nonwovens. These filled PP grades reach their end markets through a filler masterbatch far more often than as neat powder, for the dust and dispersion reasons covered in the processing section below.

One stabilization detail separates calcium-carbonate-filled PP from talc-filled PP. Talc carries Lewis-acid surface sites that can catalyse oxidation at processing and service temperatures, so a talc-filled PP compound needs a stronger package of antioxidants for plastics than an equivalent calcium-carbonate-filled one does; calcium carbonate's chemically inert carbonate surface does not present that catalytic risk. The full loading comparison between the two mineral fillers sits on fillers for polypropylene.

Calcium carbonate in polyethylene film, including breathable film#

Polyethylene film uses calcium carbonate in two different ways: as a cost-reducing filler delivered through masterbatch in carrier bags and refuse sacks, and as the pore former that makes microporous breathable film possible. In the first role, filler masterbatch is blown into film for carrier bags and refuse sacks purely to displace resin at low cost. Breathable and barrier film constructions of every kind, including this one, are covered under additives for packaging film.

In the second role, fine ground calcium carbonate is essential rather than optional: pores are nucleated around each particle as the film is biaxially stretched, which is how a nonwoven house wrap or a nappy backsheet becomes air- and vapour-permeable while staying liquid-tight. As an antiblock additive, calcium carbonate needs a far higher loading than the other antiblock additives, 2,500 to 20,000 ppm against diatomaceous earth or talc, a 250 to 300% increase, because its irregular shape is less effective per particle at keeping film layers from sticking together. Top-cut oversize particles are the leading cause of film pinholes in either role. Film-grade loadings by polymer are collected on fillers for polyethylene.

Calcium carbonate filler masterbatch and let-down#

Most converters buy calcium carbonate as a filler masterbatch rather than as powder, because a pellet dosed at the throat avoids the dust, the feeding problems and the dispersion risk of a fine mineral. Filler masterbatch for calcium carbonate typically carries 70 to 85% mineral in a PE or PP carrier, a narrower and richer band than the 40 to 65 wt% general masterbatch range (extremes 15 to 80 wt%) that applies across masterbatch types generally. The viscosity penalty of high loading is manageable with the right lubricant package: the same LLDPE study cited above showed that a 60 wt% calcium carbonate masterbatch, at about 3 times the neat resin's melt viscosity, returned to just above neat viscosity once 3 wt% wax and 1.0 wt% zinc stearate were added.

As a worked example, a filler masterbatch at 80% calcium carbonate let down at 25% gives 20 wt% calcium carbonate in the finished part (0.80 x 25% = 20%), a calculation rather than a product recommendation. Carrier resins, calcium carbonate content and melt flow index specifications for commercial grades are set out on filler masterbatch; the arithmetic above can be checked against the let-down ratio calculator.

What Goes Wrong with Calcium Carbonate? Processing and Additive Interactions#

Calcium carbonate is chemically inert, so almost every problem it causes in a compound is physical: viscosity, dispersion, abrasion, moisture and the competition for other additives on the particle surface. The table below collects the eight issues most often reported and what to do about each.

Wetting and de-agglomeration at high loading are the job of dispersing agents, which work alongside the coating chemistry rather than in place of it. The zinc stearate used in the viscosity study above is one of the metal stearates used across the industry as internal lubricants, and its effect on a calcium carbonate compound is representative of the class.

How Is the Calcium Carbonate Content of a Compound Measured?#

The calcium carbonate content of a finished compound is measured as ash: a weighed sample is burned off in a muffle furnace to ASTM D5630 or ISO 3451, and the residue is the mineral. Method A of ASTM D5630-22 uses a muffle furnace on a 5 to 50 g sample, and method B uses a rapid-ash procedure on a 2 to 10 g sample. Halogenated polymers are excluded from the ash method, which means PVC filler content is not determined by simple ashing, the detail the ranking pages on this topic never carry.

For a PVC compound where ashing is not valid, density (ISO 1183, ASTM D792) is a useful cross-check on the loading that was actually achieved, and the same figure feeds directly into the recycling float-sink question below. Filler content and the tests that decide it are covered in depth under ash content and filler content testing, thermal performance under heat deflection temperature, and whether a grade toughened or embrittled a compound under impact strength.

What Is the Regulatory Status of Calcium Carbonate in Plastics?#

Calcium carbonate is one of the least restricted additives in plastics: it is an authorised food-contact additive in the EU under FCM 21 with no specific migration limit, it is GRAS in the United States, and it carries no harmonised EU hazard classification, so the rules that actually bite are the occupational ones about dust.

REACH: why ground limestone is exempt but PCC is registered#

Ground calcium carbonate and precipitated calcium carbonate sit on opposite sides of a REACH line: mined, unmodified limestone is exempt from registration under Annex V, while precipitated grades are manufactured substances and are covered by the 296 active registrations under EC 207-439-9. Naturally occurring minerals that are not chemically modified are exempt from REACH registration under Annex V points 7 and 8, and an ECHA CHEM check shows no registration dossiers for limestone under EC 215-279-6. Calcium carbonate under EC 207-439-9, the identity PCC is registered against, carries 296 active dossiers in a joint submission, with the dossier evaluation concluded on 22 January 2016. Since Regulation (EU) 2018/1881, registrants must describe the nanoforms of a registered substance, which reaches nano-PCC. Calcium carbonate is not on the REACH Candidate List. The Annex V exemption route and the registration duties it sits beside are explained in full on REACH and plastic additives.

EU food contact: FCM 21 "carbonic acid, salts" under Regulation (EU) No 10/2011#

Calcium carbonate is authorised for plastic food-contact materials in the EU under entry FCM 21 (Ref 42500, "carbonic acid, salts") of Regulation (EU) No 10/2011, with no substance-specific migration limit, so only the overall migration limit of 10 mg/dm2 applies to the finished article. For infant articles that overall migration limit is 60 mg/kg. Calcium itself carries no Annex II metal migration limit, unlike aluminium (1 mg/kg), barium (1 mg/kg), zinc (5 mg/kg) and six other listed metals that the same annex restricts. As covered above, Article 9(2) of the same regulation allows a nanoform only where it is explicitly authorised and specified in Annex I, and FCM 21 carries no such nanoform specification. Dolomite, the closest chemical relative of calcium carbonate among mineral fillers, has its own separate entry, FCM 623. How FCM entries, migration limits and the overall migration limit work together is explained in full on EU 10/2011.

United States: 21 CFR 184.1191 GRAS and 21 CFR 178.3297#

In the United States, calcium carbonate is generally recognised as safe for direct food use under 21 CFR 184.1191 and is listed as a colorant for polymers under 21 CFR 178.3297, at levels reasonably required to accomplish the intended coloring effect. 21 CFR 184.1191 names the lime-soda process, carbonation and other manufacturing processes and applies to calcium carbonate under CAS 471-34-1. 21 CFR 178.3297 is a colorant clearance, not a filler clearance, so a 30 wt% filler loading in a food-contact polyolefin is not covered by that section on its own; filler-level use rests on the GRAS status under 184.1191 together with the polymer's own regulation, not on the colorant entry. The difference between GRAS status, prior-sanction status and a specific 21 CFR listing is set out in full on FDA food contact rules for plastic additives.

Mineral dust, occupational limits and crystalline silica in quarried grades#

The health question about calcium carbonate in a compounding plant is dust, not chemistry: the mineral itself is not classified under CLP, but quarried grades can carry respirable crystalline silica, which is regulated in the EU at 0.1 mg/m3 and by OSHA at a 50 µg/m3 permissible exposure limit. Of the 3,535 classification and labelling notifications on file for calcium carbonate, 3,180 report that the substance does not meet the GHS classification criteria. The EU binding occupational exposure limit for respirable crystalline silica is set at 0.1 mg/m3 by Directive (EU) 2017/2398, and OSHA's permissible exposure limit is 50 µg/m3 with an action level of 25 µg/m3 (29 CFR 1910.1053). Crystalline silica is listed on California's Proposition 65 list, dated 1 October 1988, and the NEPSI social-dialogue agreement, signed in 2006, sets industry good practice for handling crystalline-silica-bearing minerals. A quarried GCC deposit can carry quartz alongside the carbonate, which is the pathway that brings silica exposure into a calcium carbonate operation even though the carbonate itself is not the hazard. Which plastics chemicals are actually listed under California Proposition 65 is tracked in full on that page.

How Does Calcium Carbonate Affect Recyclability?#

Calcium carbonate is the additive most likely to push a polyolefin package out of its recycling stream, because sorting plants separate polyolefins by floating them and a filled compound above 1.0 g/cm3 sinks. Three density thresholds decide the outcome in practice.

• Mineral-filled PP above 1.0 g/cm3 sinks during float-sink separation and is removed from the polyolefin recycling stream
• PE film approaching 0.996 g/cm3 is the point at which the APR's guidance calls for testing the material against the float-sink test
• PE film above 1.00 g/cm3 is treated as non-recyclable in that stream under the same APR guidance

Under the EU's Packaging and Packaging Waste Regulation, Regulation (EU) 2025/40, recyclability performance grades make filler loading in packaging a design-for-recycling decision rather than a purely mechanical one. Density, sortability and the PPWR grades are covered in full under design for recycling, and the additive package a filled recyclate needs of its own is described on additives for recycled plastics.

Who Supplies Calcium Carbonate for Plastics?#

Calcium carbonate for plastics comes from a small group of large mineral producers, and filler masterbatch from a wider set of regional converters. The filler sector as a whole counts more than 700 producers worldwide, and the filler-masterbatch trade in particular is concentrated in Vietnam, India and Egypt.

Company data comes from our source library only. Filler masterbatch converters, which are a separate supply layer, are listed on the supplier directory.

Buyers should compare grades by median particle size, top cut, coating type and coating level, not by trade name. Plants, grades and certifications by company are in the directory of calcium carbonate and mineral filler suppliers.

---

Which Other Mineral Fillers Compete with Calcium Carbonate?#

Calcium carbonate is the default mineral filler, and every alternative is chosen for the one property it beats: talc for stiffness, wollastonite for a needle shape, barium sulfate for density and kaolin for electrical resistivity. The table below sets the physical comparison out directly.

The acicular alternative, chosen where a needle shape outperforms a blocky or platy particle, is covered on wollastonite in plastics.

Talc vs calcium carbonate#

Talc beats calcium carbonate on stiffness, heat deflection temperature and abrasion, and calcium carbonate beats talc on price, impact retention and regulatory calm. A talc platelet, at aspect ratio 5 to 40, gives far more stiffness per unit volume than a blocky calcium carbonate particle at 1 to 3, and talc's Mohs 1 hardness against calcium carbonate's Mohs 3 makes it far less abrasive to screws, barrels and dies. Talc also carries Lewis-acid surface sites that can catalyse oxidation, so a talc-filled PP compound needs a stronger antioxidant package than a carbonate-filled one.

The regulatory picture has moved recently and should be stated carefully. The ECHA Risk Assessment Committee's opinion of 20 September 2024 recommends classifying talc as Carc. 1B (H350) and STOT RE 1 (H372, lungs), but that recommendation is not yet in CLP Annex VI as of the 2026-07-01 consolidation, so it is written here as proposed, never as classified. IARC separately classified asbestos-free talc as Group 2A in 2024. Talc carries its own EU food-contact entry, FCM 615, with no specific migration limit. Loadings, the CLH proposal and the IARC classification in full detail are on talc in plastics.

Dolomite, kaolin, barium sulfate and wollastonite#

Dolomite is the closest substitute, a calcium-magnesium carbonate with its own food-contact entry (FCM 623), used where a slightly harder and denser carbonate is acceptable. Kaolin (CAS 1332-58-7, FCM 410) is chosen for electrical resistivity, and calcined kaolin specifically raises the volume resistivity of PVC wire insulation. Barium sulfate has no named FCM entry of its own and is used under Article 6(3)(a) of Regulation (EU) No 10/2011, with an Annex II barium migration limit of 1 mg/kg, chosen mainly for density, sound damping and radiopacity. Wollastonite (CAS 13983-17-0, FCM 613) is chosen for its acicular, needle-like particle shape, which no carbonate or platy mineral can match.

Calcined grades for cable insulation are on kaolin in plastics, and density and radiopacity are the reasons to pay for barium sulfate in plastics.

What are the disadvantages of calcium carbonate as a filler?#

The four real disadvantages of calcium carbonate in plastics are added weight, a limited stiffness gain because of its blocky shape, abrasion of screws and dies at Mohs 3, and the density rise that can take a filled polyolefin out of its recycling stream.

• Added weight, since the mineral is about three times as dense as the polyolefins it is most often used to fill
• A limited stiffness gain, because a blocky, low-aspect-ratio particle raises modulus far less than a platy or fibrous filler at the same loading
• Abrasion of screws, barrels and dies, driven by the mineral's Mohs 3 hardness against talc's Mohs 1
• A recycling density penalty, since a compound above 1.0 g/cm3 can sink during float-sink separation and leave the polyolefin recycling stream

Does calcium carbonate make plastic biodegradable?#

No: calcium carbonate is an inert mineral and does not make a polyolefin biodegradable, however high the loading. It changes physical properties, mass, stiffness, density and thermal conductivity, not the polymer backbone, so it plays no role in the mechanisms covered under biodegradation additives.

Is calcium carbonate filler safe in food-contact plastic?#

Yes within the rules: calcium carbonate is an authorised food-contact additive in the EU under FCM 21 with no specific migration limit, and it is GRAS in the United States under 21 CFR 184.1191, so compliance turns on the overall migration limit of the finished article rather than on the filler. The nanoform question is the one exception to treat carefully: a nanoform grade needs its own check against Article 9(2) of Regulation (EU) No 10/2011 rather than an assumption that the group entry covers it.

How much does calcium carbonate filler cost?#

Calcium carbonate is the cheapest mineral filler in common use, which is why it is bought by the tonne rather than by the kilogram, and the price a compounder pays depends far more on particle size, coating and freight than on the mineral itself. No calcium carbonate price is established in our source library. For context only, USGS 2024 average US prices for competing minerals were talc at USD 330/t, ground mica at USD 300/t, ground barite at USD 220/t and kaolin at USD 160/t; none of these figures should be read as a calcium carbonate price. Grade differences and price drivers, once a sourced figure is available, are tracked on calcium carbonate filler price.

---