A filler masterbatch is a pelletised concentrate of ground calcium carbonate in a polyethylene or polypropylene carrier resin, added to the extruder so that a converter can put mineral filler into film, sheet or mouldings without handling powder. It is the cheapest ingredient in most polyolefin converting plants, which is why the question is never whether to use it but how much the part can carry before stiffness, toughness and density move outside specification.
Filler masterbatch belongs to the delivery-form layer of plastic additives: the mineral itself is a filler, the mineral packaged into pellets for an extruder is a masterbatch, and every filler-masterbatch data sheet describes both identities at once. It is one of the five forms of masterbatch a converter buys, alongside colour, white, black and additive concentrates.
This page covers what goes into a filler masterbatch, how the let-down arithmetic works, where converters use it, what it changes in the finished part, how a lot is checked on the incoming dock, and whether it clears food-contact and recycling rules in the EU and the US. Four ingredients recur in every published formulation: the mineral filler, the carrier resin, a dispersant wax and a lubricant stearate.
Key figures
- 4 ingredients: mineral filler, carrier resin, dispersant wax and metal stearate
- Calcium carbonate: CAS 471-34-1, EC 207-439-9
- One published worked formulation: 60 wt% CaCO3 with 3 wt% polyethylene wax and 1.0 wt% zinc stearate in LLDPE (Radebe et al., 2022)
- EU food contact: calcium carbonate is FCM No. 21 in Regulation (EU) No 10/2011, with no specific migration limit
What Is a Filler Masterbatch?#
A filler masterbatch is a masterbatch whose active ingredient is a mineral filler, almost always ground calcium carbonate, compounded into a polyolefin carrier at a loading far above anything the finished part will contain. Masterbatch additive content typically runs 40 to 65 wt%, with a documented range of 15 to 80 wt% at the extremes, and filler masterbatch sits at the top of that band, because the mineral is cheap enough to carry at high concentration without hurting the economics of the concentrate itself.
The masterbatch route exists because dosing a fine mineral powder directly into an extruder is impractical for most converters. A masterbatch gives accurate dosing of the filler, produces no dust on the shop floor, has a longer shelf life than a powder blend exposed to moisture, and can be combined with a separate colour or additive masterbatch on the same feed throat. The mineral chemistry of calcium carbonate itself, its grades and particle sizes, is a separate subject from the pellet described on this page.
Filler masterbatch vs color, white, black and additive masterbatch#
Filler masterbatch differs from the other masterbatch types in one number: colour and additive concentrates are let down at roughly 1 to 5 % of the base polymer, while a filler concentrate is dosed high enough to leave a double-digit mineral content in the part. That 1 to 5 % figure belongs to colour and additive masterbatch only, and applying it to a filler grade understates the dose by an order of magnitude. All five masterbatch types share the same carrier logic: a universal wax carrier works across several base polymers, while a polymer-specific carrier such as EVA or LDPE is chosen to match the resin it goes into. Table 1 compares the five types side by side.
Table 1: masterbatch types compared
| Masterbatch type | Active ingredient | Typical let-down | Learn more |
|---|---|---|---|
| Color masterbatch | Pigments | 1-5 % | Color Masterbatch |
| White masterbatch | Titanium dioxide (TiO2) | 1-5 % | White Masterbatch |
| Black masterbatch | Carbon black (35 wt% standard for pressure pipe, let down 5-6.5 %) | 1-5 % | Black Masterbatch |
| Additive masterbatch | Functional additives (antioxidant, UV, antistatic and others) | 1-5 % | Additive Masterbatch |
| Universal masterbatch | Wax carrier compatible with several base polymers | Varies with the active ingredient carried | Universal masterbatch (page in preparation) |
Filler masterbatch vs compounding mineral filler directly#
Compounders that own a twin-screw line can meter calcium carbonate powder straight into the melt, but most film and moulding plants have only a single-screw machine, so the mineral reaches them as a pellet that a standard gravimetric feeder can handle. Direct metering of powder belongs to plastic compounding on a twin-screw line, where a side feeder can add filler downstream of the melting zone without first pelletising it.
Masterbatch producers use one of two routes to build the pellet in the first place. A split-feed line runs the carrier polymer through the main throat and adds the filler by a twin-screw side feeder placed downstream of the melting zone, for gentler wetting and fewer agglomerates, while a premix line blends all the components first and doses the mix through a volumetric feeder. Accurate low-level dosing on the converter's own line needs a gravimetric loss-in-weight feeder rather than a volumetric one; the side-feed and premix routes themselves are compared under how masterbatch is made.
What Are the 4 Ingredients of a Filler Masterbatch?#
The 4 ingredients of a filler masterbatch are the mineral filler, the carrier resin, a polymer wax that wets and disperses the mineral, and a metal stearate that lubricates the melt; the mineral filler makes up most of the weight. The published example formulation used in this section comes from Radebe, Focke and co-workers (University of Pretoria, Journal of Polymer Engineering, 2022), who compounded 60 wt% stearic-acid-coated calcium carbonate into LLDPE with a polyethylene wax dispersant and a zinc stearate lubricant. Table 2 sets out the four components at the levels reported in that study.
Table 2: worked example formulation (published source, not a commercial recipe)
| Component | Function | Level in the masterbatch | Source |
|---|---|---|---|
| Ground calcium carbonate, stearic-acid coated (1.1 % coating on filler weight) | Mineral filler | 60 wt% | Radebe et al., 2022 |
| LLDPE | Carrier resin | Balance | Radebe et al., 2022 |
| Polyethylene wax (CAS 9002-88-4) | Dispersant, viscosity reducer | 3 wt% | Radebe et al., 2022 |
| Zinc stearate (CAS 557-05-1) | Lubricant, viscosity reducer | 1.0 wt% | Radebe et al., 2022 |
Commercial grades differ. This is the one filler-masterbatch formulation in our source library with a published source; ask any supplier for their own loading, coating level and additive package.
1. The mineral filler: ground calcium carbonate#
The filler in almost every filler masterbatch is ground calcium carbonate (CAS 471-34-1, EC 207-439-9), a blocky limestone-derived mineral with a Mohs hardness of 3 that costs a fraction of polyethylene and carries no GHS hazard classification: 3,180 of 3,535 classification and labelling notifications report that the substance does not meet the GHS criteria. Ground limestone also carries CAS 1317-65-3.
- Molecular weight: 100.09 g/mol
- Density: 2.7 to 2.95 g/cm3
- Mean particle size: 0.02 to 30 micrometres, depending on grade
- Particle shape: blocky, aspect ratio 1 to 3
Two properties decide how the mineral behaves once it is in the melt. Hardness sets equipment wear: abrasion scales with Mohs hardness, so calcium carbonate at Mohs 3 wears screws and dies less than wollastonite (4.5) or silica (5.5 to 7), though more than talc (1). Particle size sets film and impact performance, and here the top cut, the d98, matters more than the median d50 for impact strength and film pinholes, because the largest particles in the distribution are the ones that start cracks or tear a thin film.
Talc is used in some grades as an alternative filler, but as a platy mineral with a higher aspect ratio it stiffens the compound more at the same loading than calcium carbonate does; no market-share figure for talc-based filler masterbatch is available in our source library. Grades, particle sizes and the GCC and PCC split are covered on calcium carbonate in plastics, and the wider family of mineral fillers, including talc and kaolin, is compared under fillers for plastics.
Coated vs uncoated calcium carbonate#
Filler masterbatch normally uses stearic-acid-coated calcium carbonate, because the fatty-acid layer turns a hydrophilic mineral surface into a hydrophobic one that the polyolefin melt can wet. The published LLDPE formulation used a grade coated at 1.1 % stearic acid on filler weight, and the coating level is one of the variables a supplier's technical data sheet should state.
| Surface | Wetting by the polyolefin melt | Typical use | |
|---|---|---|---|
| Uncoated GCC | Hydrophilic, polar | Poor, tends to agglomerate | Rarely used alone in filler masterbatch |
| Stearic-acid-coated GCC | Hydrophobic, fatty-acid layer | Wets readily, disperses at high loading | Standard for filler masterbatch |
Coating also changes mechanical behaviour, not just processability. Thio, Argon, Cohen and Weinberg (Polymer 43, 2002, 3661) and Zuiderduin, Westzaan, Huetink and Gaymans (Polymer 44, 2003, 261) found that fine, well-dispersed, stearic-acid-coated calcium carbonate below about 3 micrometres can toughen polypropylene: the particles debond from the matrix under load and the polymer ligaments between them yield instead of cracking. Coarser or poorly dispersed particles act as defect sites instead.
A silane coupling agent is not the fix here. Gelest lists calcium carbonate, along with gypsum, barytes, graphite and carbon black, among the mineral surfaces on which silane coupling agents perform poorly, which is why the industry treats the surface with a fatty acid rather than a silane. The coated grade used in most filler masterbatch is ground calcium carbonate (GCC); the manufactured, finer alternative is precipitated calcium carbonate (PCC), and filler surface treatment chemistries beyond stearic acid, including silanes and titanates, are covered under filler surface treatment.
2. The carrier resin: PE or PP#
The carrier resin decides which polymer the masterbatch can go into: a PE-carrier filler masterbatch belongs in polyethylene film and a PP-carrier grade in polypropylene mouldings and raffia, because the carrier has to melt and mix with the base resin rather than survive as a separate phase. Masterbatch carriers fall into two groups: a universal wax carrier that crosses several base polymers, or a polymer-specific carrier, with EVA or LDPE used for polyolefins and nylon. The published LLDPE example used an LLDPE carrier, matching the base resin it was designed for.
Buyers should ask for the carrier polymer and its melt flow rate on the technical data sheet, not just the CaCO3 percentage, because a carrier with the wrong melt flow relative to the base resin shows up as gels or flow lines rather than as a clean blend. Our source library holds one carrier melt-index figure, an MLDPE or LLDPE carrier below 20 melt index, but that figure comes from black masterbatch for pressure pipe and does not transfer to a filler grade. Carrier compatibility across polymers is covered on masterbatch carrier resins.
3. The dispersant: polymer wax#
Loading 60 wt% calcium carbonate into LLDPE tripled the melt viscosity in the published trial, and it took 3 wt% of a polyethylene wax together with 1 wt% zinc stearate to bring the melt back to roughly the viscosity of the unfilled polymer. The wax used was polyethylene wax (CAS 9002-88-4), an example grade with a number-average molecular weight of 4,715 Da and a weight-average of 14,960 Da, melting between 90 and 105 degrees C; the polymer wax is exempt from REACH registration as a polymer and is listed in Regulation (EU) No 10/2011 as FCM substance No. 549 for additive use.
A Fischer-Tropsch wax was also tested at 3 wt% as a drop-in replacement for the polyethylene wax and performed comparably, though the trial noted that lower-molecular-weight waxes can worsen die drool, the build-up of wax and additive residue at the die lip. Polyethylene, oxidised polyethylene and Fischer-Tropsch grades are compared under polymer waxes, and other dispersing agents for masterbatch work on the same wetting principle: lower the surface tension between the mineral and the melt so the particles separate instead of clumping.
4. The lubricant: zinc or calcium stearate#
The fourth ingredient is a metal stearate, usually zinc stearate, which melts at about 130 degrees C and spreads over the filler and the die wall as an external lubricant. Zinc stearate (CAS 557-05-1, EC 209-151-9) also acts as a dispersion aid alongside the polyethylene wax; in the published trial, magnesium stearate used alone performed worse than zinc stearate, while a blend of the two performed well.
Zinc stearate is the component that a food-contact calculation has to watch: zinc carries a specific migration limit of 5 mg/kg of food in Annex II of Regulation (EU) No 10/2011, and that limit applies to the whole finished article, not to the masterbatch in isolation. Zinc stearate melts at about 130 degrees C and doubles as a dispersion aid, and calcium stearate is the alternative where zinc has to be avoided, for example in some food-contact or medical formulations.
How Much Filler Masterbatch Do You Add?#
The amount of filler masterbatch is not a fixed percentage: it is the filler content the part is designed for, divided by the filler loading of the masterbatch. No commercial let-down range for filler masterbatch exists in our source library, so this page gives the arithmetic and two worked examples rather than a supplier's typical number, and the reader supplies the two figures a specification sheet should already carry.
Four variables drive the dose:
- Target mineral content in the finished part, set by the design or cost target
- The masterbatch's own CaCO3 loading, stated by the supplier on the technical data sheet
- The property the part has to keep, such as impact strength, elongation, transparency or weld-line strength, which sets a practical ceiling on the dose
- Density and cost per unit volume rather than cost per kilogram, because a heavier, mineral-filled compound needs less volume, not less weight, to fill the same mould or cover the same film area
Run your own numbers in the let-down ratio calculator once the target mineral content and the masterbatch's CaCO3 percentage are known. Typical dosage bands for every additive family are listed under additive dosage levels in plastics, which puts the filler-masterbatch dose in context against the 1 to 5 % range used for colour and additive concentrates.
How to calculate the calcium carbonate content of the finished part#
Filler in the part equals the masterbatch's CaCO3 loading multiplied by the masterbatch's fraction of the blend. That single multiplication is the whole calculation; everything else is unit bookkeeping.
The arithmetic scales the same way a similar calculation does for black masterbatch in pressure pipe, where a 35 wt% carbon black concentrate let down at 5 to 6.5 % gives 1.75 to 2.3 % carbon black in the finished pipe.
Two worked examples show the calculation for a filler grade:
- A masterbatch holding 70 wt% CaCO3, added at 20 % of the blend, gives 0.70 multiplied by 20 %, or 14 wt% CaCO3 in the part. This is an arithmetic example only, not a recommended masterbatch grade or dose.
- The published 60 wt% formulation (Radebe et al., 2022), added at 25 % of the blend, gives 0.60 multiplied by 25 %, or 15 wt% CaCO3 in the part, plus 0.75 wt% polyethylene wax and 0.25 wt% zinc stearate carried in with it. Converters who calculate only the mineral content and forget the wax and stearate riding along with it will find their compound's other property targets drift.
Both let-down conventions describe the same blend: "20 % of the blend" is the same as "1 part masterbatch to 4 parts resin" (a 4:1 ratio), and a specification should state the percentage and the ratio together so the two never get confused on the shop floor. Both conventions, and the phr-to-wt% conversion behind them, are defined on PHR, wt% and let-down ratio.
Which Products Use Filler Masterbatch?#
Filler masterbatch is used wherever a polyolefin part is thick enough or dull enough to carry mineral: blown film and carrier bags, refuse sacks, breathable film, thermoformed trays, housewares and woven raffia sacks. Table 3 sets out the base polymer and the filler content reported in our source library for each application, alongside the specification fields a buyer should request from a supplier rather than assume.
Table 3: applications and specification fields
| Application | Base polymer | Filler content reported in our source library | Spec fields to request from the supplier |
|---|---|---|---|
| Blown film, carrier bags, refuse sacks | LDPE / LLDPE / HDPE | No sourced figure | CaCO3 %, carrier and its MFR, top cut d98, moisture, ash content, pellet size |
| Breathable microporous film | LLDPE | No sourced figure | Particle size distribution, coating type, moisture |
| Injection moulding and thermoforming | PP | Often 20-40 % in the compound | CaCO3 %, carrier MFR, top cut, ash |
| Raffia tape and woven sacks | PP | No sourced figure | CaCO3 %, top cut d98, moisture, filter pressure value |
| PVC (reference, not a masterbatch route) | PVC | Drainpipe 15-20 %, window profile 5-15 % coated, cable up to 70 phr | Not applicable; PVC is dry-blended |
The loading figures are compound loadings from primary and encyclopaedic sources, not masterbatch loadings. We publish no let-down ranges because no sourced figure exists; ask the supplier for theirs.
Request quotes for filler masterbatch, covering CaCO3 content, carrier polymer, application, monthly volume and country, through the plastic additive supplier finder.
Blown film, carrier bags and refuse sacks#
Blown film is the largest outlet for filler masterbatch: carrier bags, refuse sacks and liner film take mineral because the film is opaque anyway and the saving goes straight into the cost per bag. Our source library holds no maximum filler level for blown film, so the practical ceiling is qualitative: pinholes, tear strength and bubble stability set the limit long before any regulatory rule does, and the spec fields in Table 3 are what a buyer checks before raising the dose.
Particle top cut controls most of that ceiling, because the largest particles in the distribution are what punches a pinhole in a thin film. Gels and unmelted concentrate in the finished film usually trace back to poor masterbatch dispersion rather than to the resin, and the fixes are smaller masterbatch pellets, tighter screen packs on the extruder, or a carrier change. Which minerals suit PE film is covered on fillers for polyethylene, and the rest of the packaging-film additive package, antioxidant, slip, antiblock and UV protection where the film is used outdoors, is on additives for packaging film.
Breathable and microporous film#
Breathable film is the one application where the mineral is the functional ingredient rather than a cost saving: the film is stretched after extrusion and micropores open at each calcium carbonate particle, so the sheet passes water vapour but not liquid water. The mechanism depends on fine ground calcium carbonate, used in products such as diaper backsheets and construction house wrap, where the pore network has to form uniformly across the whole stretched area.
No figure for filler loading, particle size or stretch ratio in breathable film sits in our source library, so this page describes the mechanism rather than a target percentage; a supplier's technical data sheet for a breathable-film grade should state all three.
Injection-moulded and thermoformed polypropylene#
Polypropylene housewares, crates and thermoformed trays run at calcium carbonate levels that are often quoted as 20 to 40 % of the compound, a band wide enough that the exact figure has to come from the part specification rather than from a rule of thumb. The same filler-masterbatch route supplies fibres and nonwovens at comparable loadings.
Particle size, not just loading, decides whether the mineral helps or hurts. Fine, coated calcium carbonate below about 3 micrometres can raise notched impact strength in polypropylene by the debonding and matrix-yielding mechanism described above, while a coarser grade mainly adds stiffness and cost saving without the toughening effect. At the same loading, talc gives more stiffness than calcium carbonate, because a platy particle with a higher aspect ratio reinforces the matrix more efficiently under the Halpin-Tsai model (Halpin and Kardos, Polymer Engineering and Science 16, 1976, 344). Talc and CaCO3 loadings in PP are compared on fillers for polypropylene, and release, nucleation and flow additives used alongside filler masterbatch in the same mould are on additives for injection molding.
Raffia tape, woven sacks and sheet#
Woven polypropylene sacks are made from stretched tape, and stretched tape is the least forgiving product for a filler masterbatch, because every oversized particle is a break point in a filament a few tens of microns thick. Raffia tape, woven sacks and sheet share the same top-cut sensitivity as blown film, but at a smaller cross-section, so the same d98 specification matters even more here than in a thicker film.
Oversized particles act as defect sites at the point where the tape is drawn down to its final width, and a supplier's top-cut figure is one of the most useful spec fields a raffia converter can request before switching filler-masterbatch grades.
What Does Filler Masterbatch Do to the Plastic?#
Filler masterbatch raises stiffness, opacity, heat transfer and density, and it lowers the cost per kilogram; what it takes away is elongation, impact resistance at poor adhesion, and part of the cost saving once the higher density is counted per litre instead of per kilogram. Every one of those changes has a distinct mechanism, and Table 4 sets them out property by property.
Stiffness rises with the filler's volume fraction and its aspect ratio, a relationship the Halpin-Tsai model describes (Halpin and Kardos, 1976); a blocky mineral like calcium carbonate stiffens the compound less than a platy one like talc at the same loading. Strength behaves differently: it depends on how well the particle bonds to the matrix. Pukanszky's model (Composites 21, 1990, 255) quantifies that interaction: poorly bonded particles lower tensile strength, while fine, well-dispersed, coated calcium carbonate below about 3 micrometres can raise notched impact strength in polypropylene through the debonding and matrix-yielding mechanism reported by Thio et al. (2002) and Zuiderduin et al. (2003).
The physical changes are more predictable. Calcium carbonate has a density of 2.7 to 2.95 g/cm3 against roughly 0.91 to 0.96 g/cm3 for the polyolefins it replaces, so a filled part is heavier for the same volume, and it scatters light more than the polymer alone, raising opacity. Melt viscosity rises too, by a factor of about 3 at 60 wt% CaCO3 before the wax and stearate package corrects it. Omya states that calcium-carbonate-filled polymers transfer heat more quickly than the neat resin, which can raise line speed, and that calcium carbonate can replace up to 60 % of the polymer in some finished articles; both are supplier claims, not independently sourced figures.
The single most useful rule for a buyer sits in the cost line: filler lowers the cost per kilogram, but because the filled compound is denser, the cost per litre falls by less than the cost-per-kilogram figure suggests, so a like-for-like comparison has to be run on cost per unit volume, not on price per kilogram. How the strength and toughness trade-off is actually measured is explained on impact strength (Izod, Charpy).
Table 4: property effects of filler masterbatch
| Property | Direction | Mechanism and source |
|---|---|---|
| Stiffness / modulus | Up | Volume fraction and aspect ratio (Halpin-Tsai) |
| Tensile strength | Depends on adhesion | Poorly bonded particles lower it (Pukanszky, 1990) |
| Notched impact strength in PP | Can rise with fine coated grades below about 3 micrometres | Debonding and matrix-ligament yielding (Thio 2002; Zuiderduin 2003) |
| Density | Up | CaCO3 2.7-2.95 g/cm3 vs 0.91-0.96 g/cm3 for polyolefins |
| Opacity | Up | Mineral scatters light; calcite refractive index 1.6584 |
| Melt viscosity | Up | About 3x at 60 wt% before lubricants are added |
| Line speed | Can rise | Faster heat transfer (Omya claim) |
| Equipment wear | Up | Mohs hardness 3 |
| Cost per kilogram vs cost per litre | Down, but less per litre | Density rises, so cost per litre falls less than cost per kilogram |
How Do You Check the Quality of a Filler Masterbatch Lot?#
A filler masterbatch lot is judged on 5 measurements: calcium carbonate content, melt flow rate, particle top cut, moisture and dispersion. None of these has a universal pass or fail value in our source library for filler masterbatch, because no sourced spec range exists yet; what a buyer can do is request the measured value on every lot and compare it against the supplier's own technical data sheet.
- Calcium carbonate content confirms the masterbatch matches the loading on the data sheet, usually by ash content or thermogravimetric analysis, since an under-loaded lot changes every downstream calculation in the how-much section above.
- Melt flow rate, tested to ISO 1133 or ASTM D1238, is the quickest incoming check on a masterbatch lot and catches a carrier or additive-package change before it shows up as a processing problem.
- Particle top cut (the d98) matters more than the median particle size for impact strength and film pinholes, because the largest particles in the distribution are the ones that start cracks or punch holes.
- Moisture matters because carbonate fillers carry water into the extruder; excess moisture shows up as voids, splay or hydrolysis in sensitive resins, which is why converters running high filler loadings also run a desiccant masterbatch alongside it.
- Dispersion, rated in the masterbatch industry on a 1 to 5 microdispersion scale (1 best) on thin PE film, roughly 1.5 mil, a practice documented for black masterbatch in pressure pipe and applied across the masterbatch industry more broadly; the filter-pressure and microdispersion methods behind that scale are explained on dispersion testing of pigments and masterbatch.
Gels and fisheyes in the finished film trace back to degraded or crosslinked polymer, unmelted resin or concentrate, poor masterbatch dispersion, excessive heat, shear or residence time, or a weak antioxidant package, and the fix is usually smaller masterbatch pellets, a tighter screen pack or a carrier change rather than a different filler grade.
Is Filler Masterbatch Allowed in Food-Contact Plastics?#
A filler masterbatch can be used in food-contact plastics in both the EU and the US, but compliance is decided component by component: the calcium carbonate itself is the easy part, and the carrier, the coating and the stearate are what a declaration of compliance has to cover. None of the four ingredients is individually banned from food contact, but each one carries its own listing, and the finished article still has to meet the overall migration limit regardless of which additive contributes to it.
The two sections below work through the EU and US routes component by component, because a masterbatch that clears the EU list is not automatically cleared for the US route, and the reverse is also true.
EU: Regulation (EU) No 10/2011 applies to every component#
In the EU, calcium carbonate is listed in Annex I of Regulation (EU) No 10/2011 as FCM substance No. 21 (carbonic acid, salts), reference number 42500, with no specific migration limit, so the mineral itself does not constrain a food-contact filler masterbatch. The stearic-acid coating on the filler is covered too: stearic acid is FCM No. 106 (Ref 24550), authorised as both an additive and a monomer, and the polyethylene wax dispersant is FCM No. 549 (Ref 80000) for additive use, also with no specific migration limit, and exempt from REACH registration as a polymer.
Table 5: EU food-contact status per component
| Component | CAS | EU 10/2011 status |
|---|---|---|
| Ground calcium carbonate | 471-34-1 (EC 207-439-9) | FCM 21, Ref 42500 (carbonic acid, salts), additive, no specific SML |
| Stearic-acid coating | Stearic acid, FCM 106 | FCM 106, Ref 24550, authorised as additive and monomer |
| Zinc stearate | 557-05-1 | Covered as a salt of authorised stearic acid under Art. 6(3)(a); zinc SML(T) 5 mg/kg in Annex II |
| Polyethylene wax | 9002-88-4 | FCM 549, Ref 80000, additive use, no specific SML; polymer, exempt from REACH registration |
| Carrier resin (PE, PP) | Not applicable | Governed by the polymer rules of 10/2011, not by an Annex I additive entry |
Overall migration limit 10 mg/dm2; generic SML 60 mg/kg where no specific limit applies. Nanoforms need an explicit Annex I authorisation under Article 9(2).
Zinc is the constraint in practice. A zinc-stearate-lubricated masterbatch contributes to the zinc specific migration limit of 5 mg/kg set in Annex II of Regulation (EU) No 10/2011, as amended by Regulation (EU) 2020/1245, and that limit is a per-article limit, checked against the whole finished formulation, not against the masterbatch in isolation. The overall migration limit for the finished article is 10 mg/dm2, and the generic specific migration limit where no substance-specific figure applies is 60 mg/kg. Ultrafine and nano-grade calcium carbonate sits outside the FCM 21 entry unless the nanoform is explicitly authorised and specified in Annex I under Article 9(2). The full set of migration limits and the overall migration rule are explained on EU 10/2011, and the complete compliance workflow for a food-contact formulation is on additives for food packaging.
US: the 21 CFR routes for calcium carbonate#
In the US, calcium carbonate reaches food-contact plastics by two different routes: it is generally recognised as safe under 21 CFR 184.1191, and it appears in the colorant list of 21 CFR 178.3297, which names calcium carbonate among the filler minerals usable as a colorant for polymers. The 178.3297 route limits the use level to the amount needed for the colouring effect, which is not a route for a filler masterbatch dosed at 15 wt% or more; the GRAS listing under 184.1191, combined with the finished-article migration rules, is the route that actually covers a filler-masterbatch application. No US maximum use level for calcium carbonate as a filler sits in our source library, so a converter selling into the US market confirms the specific 21 CFR basis with the supplier rather than assuming one route covers every use.
Zinc stearate is GRAS under 21 CFR 182.8994 in the US, the parallel route to its EU coverage as a salt of an authorised additive.
Does Filler Masterbatch Affect Recyclability?#
Mineral filler changes how a part behaves in a recycling plant before it changes anything else: calcium carbonate has a density of about 2.7 to 2.95 g/cm3, and once a polypropylene part passes 1.0 g/cm3 it sinks in the float-sink tank that is supposed to separate it from PET and PVC. That single density fact is the mechanism behind most of the recyclability discussion around filler masterbatch; the mineral itself is not the regulatory problem, the density it adds is.
Three effects follow from that mechanism:
- Sorting: a heavily filled polypropylene part can sink alongside denser polymers in a float-sink separation line instead of floating with the rest of the PP stream, misrouting it at the sorting stage.
- Design-for-recycling scoring: filler loading in packaging is becoming a factor in the recyclability grading introduced under the Packaging and Packaging Waste Regulation (EU) 2025/40, which applies from 12 August 2026.
- Restricted substances: the same regulation caps the sum of lead, cadmium, mercury and hexavalent chromium in packaging at 100 mg/kg under Article 5(4), a limit that a mineral filler and its additive package have to be checked against alongside every other packaging component.
The specific density or filler-content thresholds that recyclability certification schemes apply to a filled polyolefin part could not be verified against a primary source at the time of writing, so this page states the mechanism rather than a percentage cutoff. Density, sorting and additive effects across the whole recycling chain are mapped under design for recycling.
Who Supplies Filler Masterbatch?#
Filler masterbatch comes from two different kinds of company: the global masterbatch houses that also sell colour and additive concentrates, and a large regional industry of dedicated filler-masterbatch plants close to the limestone and to the converters. Ampacet, Avient and Tosaf are examples of the first group: Avient formed as PolyOne on 31 August 2000 and added Clariant's masterbatch business in 2020, and Tosaf runs 22 sites and about 1,600 employees across more than 50 countries. The calcium carbonate itself comes from mineral producers such as Omya, founded in 1884 and headquartered in Oftringen with about 9,000 employees, alongside Imerys, Minerals Technologies (through its Specialty Minerals brand) and Huber.
The regional plants that dominate search results for this topic, across South-East Asia, Egypt, India and China, are a real and large part of the supply base, but this page does not list individual regional suppliers, because they sit outside our verified records; the directory of filler masterbatch manufacturers covers that ground. Buyers should compare offers on CaCO3 content, carrier polymer, top cut and moisture, not on price per kilogram alone, because a cheaper pellet with a coarser top cut is paid for again in film breaks. The global houses that also sell colour, white and black concentrates are listed under masterbatch manufacturers.
Request quotes for filler masterbatch, covering CaCO3 content, carrier polymer, application, monthly volume and country, through the plastic additive supplier finder.
What Other Masterbatches Does a Filled Compound Need?#
A filled polyolefin still needs the rest of its additive package: filler masterbatch replaces resin, not antioxidants, slip, antiblock or UV protection, and each of those normally arrives as its own concentrate. The polyolefin package described elsewhere on this site combines an antioxidant with a phosphite co-stabiliser, an acid scavenger, slip and antiblock in film, and a UV stabiliser where the part is used outdoors, and a filled compound needs all of them regardless of the mineral content.
Calcium carbonate itself shows up a second time in that package, as an antiblock rather than as a filler: trial dosage for that role runs 2,500 to 20,000 ppm, a level 250 to 300 % higher than diatomaceous earth or talc need for the same effect, because the particle has to be large enough to space the film surfaces apart without acting as a bulk filler. The complete additive package for a polyethylene film is on additives for polyethylene, and calcium carbonate also appears as an antiblock, at ppm levels, under antiblock additives.
Filler masterbatch in PVC and other polymers#
PVC is the largest user of calcium carbonate among plastics, but it almost never uses a filler masterbatch, because rigid PVC is dry-blended as a powder and the mineral is simply another ingredient in the blender rather than a melt-compounded concentrate. Loadings run 15 to 20 % in unplasticised PVC drainpipe, 5 to 15 % (stearate-coated) in window profile, and up to 70 phr in PVC cable compounds, all added as a dry powder rather than through a pellet.
Calcium carbonate does one more job in PVC beyond bulking the compound: it scavenges hydrogen chloride released as the resin degrades during processing, a secondary function the mineral does not perform in the polyolefins covered above. PVC loadings and the acid-scavenging effect are covered on fillers for PVC, and the equivalent additive package for polypropylene is on additives for polypropylene.
What is the difference between filler masterbatch and calcium carbonate powder?#
Calcium carbonate powder is the mineral; filler masterbatch is that mineral already dispersed, coated, lubricated and pelletised in a carrier resin, so it can be dosed on a standard feeder without dust. In South-East Asia the product is sometimes called "taical" in trade conversation, though that is regional usage rather than a technical term. Buyers researching either term are usually asking the same underlying question: how does the mineral get into the plastic, and the pellet form is the answer for every polyolefin converter without a twin-screw compounding line.
Does filler masterbatch weaken plastic?#
It depends on the property and on the particle: stiffness rises with mineral content, while elongation at break falls, and impact strength can go either way, because well-bonded fine coated particles toughen polypropylene while oversized agglomerates start cracks. A supplier's particle-size and coating specification, not the CaCO3 percentage alone, decides which side of that trade-off a given grade lands on.
How much does filler masterbatch cost?#
Filler masterbatch is priced between the mineral and the resin it replaces, so its value to a converter moves with the polyolefin price rather than with the limestone price. The main cost drivers are the mineral price, the carrier resin price, the CaCO3 percentage, the coating level and freight, since the product is heavy and low-value relative to its shipping weight. This page publishes no price figure; mineral price drivers are tracked on calcium carbonate filler price.
What is the HS code for filler masterbatch?#
We do not publish a tariff code for filler masterbatch: classification depends on the exact composition and on the importing country's ruling, and our source library holds no verified entry, so ask your customs broker. Import-data services file related products under HS sub-chapter 3824, an observation about how a third-party database groups the trade, not a legal classification a converter can rely on.
Every figure on this page is checked against primary sources; see our methodology and fact-checking process.