Dispersing Agents for Plastics and Masterbatch: 5 Types, Mechanisms, Dosage and Selection

Dispersing agents for plastics and masterbatch are waxes, metal soaps, amides, esters and polymeric surfactants that wet pigment and filler agglomerates, break them down in the melt and stop them re-forming, and they fall into 5 types. A colour masterbatch carries 40 to 65 % pigment and is let down into the base polymer at 1 to 5 %, so what keeps a pigment at that loading from travelling through the whole process as agglomerates?

The 5 types are polyolefin waxes as the melt-viscosity carrier, amide waxes as the interfacial amide, metal soaps as the polar soap, fatty-acid and polyglycerol esters as the surfactant ester, and polymeric dispersants as the anchored polymer. Three outcomes follow a correct choice: higher colour strength, a lower filter pressure value and fewer screen changes, all three recorded by Clariant and Palsgaard. This page covers additives compounded into a polymer melt, not dispersants for paints, inks, textiles, drilling fluids or oil spills.

Everything below follows the same type order: dispersion against distribution, the mechanism, the 5 types and their comparison, dosage with its base named, the match to pigment, filler and polymer, the failure modes, 6 selection criteria, the EN 13900 and ISO 18553 test layer, the food-contact matrix, the producers and the 9 substances. Dispersing agents belong to the processing-modifier group of plastic additives, next to lubricants, processing aids and antiblock additives.

Table T1. The 5 types of dispersing agents used in plastics and masterbatch, compared by mechanism, example chemistries, typical host systems and typical level in the concentrate.

All levels are supplier recommendations or single-study values, and all of them are shares of the concentrate, not of the finished part. Row 5 is named from the class taxonomy only: our source library holds no verified grade, dosage or regulatory record for polymeric dispersants in plastics.

What Is a Dispersing Agent in Plastics?#

A dispersing agent in plastics is a wax, metal soap, amide, ester or polymeric surfactant that wets pigment and filler agglomerates in a polymer melt, lowers the melt viscosity of a highly loaded concentrate and keeps the freed particles apart afterwards, and its effect is measured as filter pressure value and colour strength. Supplier literature also calls the class dispersing aid, wetting and dispersing additive and pigment dispersing aid.

Which dispersants are then not plastic additives? The wetting and dispersing additives sold for paints, inks and coatings work in a liquid vehicle with solvent present and settling times measured in days, so they sit outside this reference. PVC plastisols and liquid thermosets sit on the border, and count as plastics only where the additive is compounded into the polymer.

Dispersion and distribution: two different mixing jobs#

Dispersion and distribution are two different jobs: dispersive mixing breaks an agglomerate down to its primary particles and needs a stress higher than the cohesive strength holding it together, while distributive mixing only spreads the particles evenly through the melt. A dispersing agent acts on the first job, a screw element or a static mixer mostly on the second.

The two mixing definitions are set out below.

• Dispersive mixing: breaking agglomerates of solid particles, such as pigments and fillers, or of droplets, down to their smallest units, which requires stress above the cohesive strength of the agglomerate.
• Distributive mixing: spreading those particles or droplets uniformly through the melt volume, without any reduction in particle size.

Table T2. Dispersive and distributive mixing compared across 4 properties.

Compounding needs both jobs plus appropriate heat management. Coperion reports that side-feeding pigments into an established melt gives "extremely gentle wetting of the pigments thus avoiding agglomerations". Both jobs are done in the same machine, as set out in plastic compounding.

Dispersing agent, wetting agent or carrier wax: what is the difference?#

A wetting agent only displaces air from the pigment surface, a dispersing agent also breaks the agglomerate and keeps the particles apart, and a carrier wax additionally forms part of the concentrate's matrix. The sequence has three steps in that order: wet the surface and displace the trapped air, break the agglomerate under shear, then coat the freed particles so they do not re-agglomerate. A wetting agent stops after step one. A dispersing agent completes all three.

The carrier is a separate role that the same molecule can also fill. A masterbatch carrier is the polymer or wax in which the colorant is dispersed, and Clariant describes its Licocene metallocene polyolefin waxes as acting as both dispersion aid and carrier, "permitting higher pigment and additive loadings, lower processing temperatures and reduced shear". A universal masterbatch uses a wax carrier so one concentrate runs in more than one base polymer, and the carrier is defined on masterbatch.

Is a dispersing agent the same as a coupling agent?#

No: a coupling agent forms a chemical bond between the filler surface and the polymer, while a dispersing agent is only adsorbed on the particle, although titanates such as isopropyl triisostearoyl titanate do both at once, and the bonding chemistries are compared on coupling agents for filled and reinforced plastics. Isopropyl triisostearoyl titanate, CAS 61417-49-0, sold by Kenrich Petrochemicals as Ken-React KR TTS, reacts through its isopropoxy group with surface protons of the filler and needs no surface hydroxyl group, and the hydrophobic isostearate chains it leaves behind lower melt viscosity and improve dispersion. The two classes are not interchangeable, which is why portal guides that treat them in one document still separate a chemical bond from adsorption.

How Do Dispersing Agents Work?#

Dispersing agents work in 3 steps: they wet the pigment surface and displace the air trapped in the agglomerate, they lower the viscosity of the highly loaded melt so the screw can transmit enough stress to break the agglomerate, and they coat the freed particles so these do not re-agglomerate before the concentrate is let down. The same three steps are usually described for a liquid paint or ink. In a polymer melt there is no solvent, the stress comes from the screw rather than from a bead mill, and the stabilisation has to survive a second heat history during the let-down.

Wetting: displacing air from the pigment surface#

Wetting comes first because a dry pigment agglomerate is full of air: the dispersant has to replace that air at the particle surface before any shear can break the agglomerate apart. An agglomerate is a loose cluster of primary particles held by surface forces, with air in every void, and a melt that cannot enter those voids pushes the whole cluster along instead.

How much dispersant a particle needs follows from its surface. Oil absorption, in grams of oil per 100 g of filler under ISO 787-5 and ASTM D281, is the proxy for binder demand and for the viscosity a loading produces, and BET specific surface area drives melt viscosity in the same direction. Oil absorption and specific surface area are defined under filler properties: particle size, surface area and oil absorption.

Deagglomeration and viscosity reduction in the melt#

A dispersant lowers the melt viscosity of the concentrate, and that is what lets the screw break the agglomerates: in a 60 wt% calcium carbonate masterbatch in LLDPE, 3 wt% polyethylene wax with 1 wt% zinc stearate returned the melt viscosity to just above that of the neat polymer, whereas the filled melt without additives was about three times more viscous. Radebe and colleagues reported those viscosity figures in 2022. The mechanism is indirect and often misread: the wax does not tear the agglomerate apart, it keeps the melt processable at a loading where an untreated compound stalls or overheats.

Dispersive mixing needs stress above the cohesive strength of the agglomerate, so an additive helps only while the transmitted stress stays above that threshold. Clariant states the same trade commercially for Licocene, which permits higher pigment and additive loadings at lower processing temperatures and reduced shear.

Why pigments re-agglomerate without a dispersant#

Freed pigment particles re-agglomerate as soon as the shear stops, because the same surface forces that built the agglomerate are still acting, so the dispersant has to stay adsorbed on the particle through the rest of the process. The concentrate is cooled, pelletised, stored and remelted at the converter, and each step gives the particles time to find one another again.

Re-agglomeration costs 4 things, all of them measurable.

• Colour strength, because pigment locked inside an agglomerate contributes no colour
• Filter pressure, which rises as agglomerates accumulate on the screen pack
• Screen changes, which stop the line
• Specks, which appear in the part and in film as visible defects

Clariant reports that 10 % Ceridust 3620 micronised wax in a masterbatch allows a pigment reduction without loss in colour strength, which turns the first item into a raw-material saving.

5 Types of Dispersing Agents for Plastics and Masterbatch#

The 5 types of dispersing agents used in plastics and masterbatch are polyolefin waxes, amide waxes, metal soaps, fatty-acid and polyglycerol esters, and polymeric dispersants. The order runs from the highest-tonnage and best-documented chemistry to the least documented one, which is also the order in which a masterbatch formulator escalates when a first formulation fails to disperse. Every type below names its chemistry, its grades and its level with the base of that level stated in the same sentence.

1. Polyolefin waxes: PE wax, oxidised PE wax and Fischer-Tropsch wax#

Polyolefin waxes are low-molar-mass polyethylene, oxidised polyethylene and synthetic Fischer-Tropsch hydrocarbons that wet pigment and filler surfaces and cut the melt viscosity of a highly loaded concentrate, and they are the highest-tonnage dispersant chemistry in masterbatch. Polyethylene wax, CAS 9002-88-4, is a non-polar hydrocarbon with a broad molar-mass distribution averaging up to about 10,000 g/mol, and it serves as external lubricant, dispersant and carrier at once. Oxidised polyethylene wax, CAS 68441-17-8, carries polar groups that anchor it to metal and give strong release at very low dosage. Fischer-Tropsch wax is a synthetic hydrocarbon of roughly 200 to 1,000 g/mol, and an experimental Sasol grade at Mn 776 and Mw 786 Da has a polydispersity of 1.01.

Grades differ widely inside the class. STRUKTOL PE(H)-100 melts at 90 to 105 °C at a specific gravity of 0.91, Baerolub PA-L at 102 to 110 °C and Baerolub L-KO at 100 to 105 °C. Among the oxidised grades, STRUKTOL PE(O)-300 runs at 6,000 to 14,000 cps at 150 °C with a dropping point of 131 °C and PE(O)-600 at 320 to 400 cps with a dropping point of 99 to 108 °C. The full wax family, including montan grades, is on polymer waxes.

Two limits apply. The lowest-molar-mass fractions must be removed by the producer to avoid a low flash point, migration and equipment build-up, and Mhlabeni reported in 2024 that lower-molar-mass Fischer-Tropsch waxes can worsen die drool relative to PE wax.

2. Amide waxes: ethylene bis stearamide (EBS)#

Amide waxes are bis-amides, in practice almost always ethylene bis stearamide (CAS 110-30-5), whose melting range of 135 to 146 °C keeps them at the interfaces between melt, metal and particle, where they lubricate and disperse at the same time. Ethylene bis stearamide carries EC number 203-755-6, the formula C38H76N2O2 and a molar mass of 593.0 g/mol, with the melting range recorded by PubChem. It is a secondary bis-amide, so it does not bloom to the film surface the way erucamide does.

The trade names are Kemamide W-40 and W-39 from PMC Biogenix, Advawax 280, STRUKTOL TR EBS and Baerolub L-AK. EBS works as lubricant and as pigment and filler dispersant in ABS, PS, PVC, polyolefins and engineering plastics, and it is a standard component of color masterbatch formulations and filled polypropylene. Struktol places its EBS-replacement blend TR 251 at 0.5 to 2.0 % of the ABS, PVC or PS compound, the closest published level for the class.

Newer amide blends are benchmarked against EBS. Its family assignment differs between sources: our source library files it under lubricants while one inventory reading places it with the slip agents, and its dominant plastics roles are lubricant and dispersant.

3. Metal soaps: calcium stearate and zinc stearate#

Metal soaps are the stearate salts of calcium and zinc, which wet both the pigment and the hot metal of the screw and the die, and in colour concentrates they are used as dispersion aids alongside a wax rather than instead of one. Calcium stearate, CAS 1592-23-0 and EC 216-472-8, wets hot metal preferentially through its polar carboxylate group, a mechanism Rabinovitch and colleagues described in 1984, and it is listed for pigment wetting in colour concentrates as well as for acid scavenging in polyolefins at 0.05 to 0.20 % of the polymer. Zinc stearate, CAS 557-05-1 and EC 209-151-9, is recorded as a dispersion aid in colour concentrates, and Baerlocher attributes that to its melting point near 120 °C, which lets it spread evenly as the compound heats.

The commercial names are CEASIT and LIGASTAR CA for the calcium soap and ZINCUM and LIGASTAR ZN for the zinc soap. Struktol gives 0.5 % of the compound as the general use level for zinc stearate, and in the 60 wt% CaCO3 LLDPE masterbatch of Radebe and colleagues it was 1.0 wt% of the concentrate alongside 3 wt% wax. The lubricant and stabiliser roles of the same soaps are on metal stearates.

Kisuma claims, as a supplier, that calcium stearate forms hygroscopic calcium chloride when it neutralises catalyst chloride, raising water carry-over in raffia tape, and that migrating metal soaps can disturb metallisation and lamination in BOPP.

4. Fatty-acid and polyglycerol esters#

Fatty-acid and polyglycerol esters are non-ionic surfactants whose polar head adsorbs on the pigment while the fatty chain reaches into the polymer, and the plant-based polyglycerol ester Einar 103 is used at 1 to 5 % of the colour masterbatch formulation in PE, PP, PVC, PET and PA. Palsgaard supplies Einar 103 as a pigment dispersing aid, and the mechanism recorded for the class is pigment wetting followed by stabilisation. The same chemistry serves as an antifog additive in PP and PE film, so the grade designation rather than the class name decides what a product does.

The class is thinly documented next to the waxes: one member carries a discrete identity here, triglycerol monostearate at CAS 26855-43-6, while the group is described by class rather than by a single CAS number. That is a reporting limit rather than a performance limit, because the food-contact route is fully established.

Stearic acid, CAS 57-11-4, enters by a different door: it is applied as a surface coating on calcium carbonate at about 1.1 % on filler weight in a grade characterised by Radebe and colleagues, rather than dosed into the compound. Stearic acid does the same job at the filler producer, as described under filler surface treatment.

5. Polymeric dispersants and hyperdispersants#

Polymeric dispersants are molecules with anchor groups that adsorb on the pigment and polymer chains that hold the particles apart by steric repulsion, and they are the one type of the 5 for which this reference has no verified grade data yet. The class sits in the family taxonomy beside the waxes, the amide, the metal soaps and the polyglycerol esters. The well-documented polymeric dispersants, including the DISPERBYK and Anti-Terra lines, are coatings products outside the border of this reference. No grade, dosage, food-contact route or supplier is stated here for a polymeric dispersant in plastics, because none is established.

Wax, Soap or Ester: How Do the Types Compare?#

The 5 types divide by what they contribute to the concentrate: polyolefin waxes carry the pigment loading and cut melt viscosity, amide waxes work at the interfaces, metal soaps wet the particle and the metal, esters suit high-surface-area organic pigments, and polymeric dispersants are the least documented route.

Table T3. The 5 dispersing agent types compared across 7 properties, in the type order used throughout this page.

Cost cannot be quantified here, because our source library holds no price, market size or growth rate for any dispersing agent used in plastics. The compliance column carries the decision instead: 4 of the 5 types have a complete EU and US food-contact route, the fifth has none, and that settles a food-packaging concentrate before any commercial discussion begins.

How Much Dispersing Agent Does a Masterbatch Need?#

A colour masterbatch takes 1 to 5 % of a polyglycerol-ester dispersing aid or about 3 wt% of a polyolefin wax with 1 wt% of a metal soap, and every one of those numbers is a share of the concentrate, not of the finished part. That distinction is the most common reading error in published dispersant data: supplier literature quotes the concentrate level and the reader applies it to the compound.

Table T4. Dispersant levels by substance and system, with the basis of every figure stated.

Our source library holds no dispersant level for polymeric dispersants and no verified level for any dispersant in engineering-plastic concentrates beyond the TR 251 blend.

The last two rows are labelled lubricant use for a reason. The same two waxes appear in rigid PVC at a fraction of a phr, where the job is metal release rather than pigment wetting, and merging those phr figures into the masterbatch range gives a dosage wrong by a factor of ten.

A filled system moves the numbers again, because the dispersant level tracks the filler loading rather than the polymer. The concentrate itself is described on filler masterbatch, and the 3 wt% wax plus 1 wt% soap combination applies at 60 wt% calcium carbonate. Levels for every additive family are on additive dosage levels in plastics.

Dosage in the concentrate versus dosage in the finished part#

Every dispersant percentage published by a supplier is a share of the concentrate, and the concentrate itself is only 1 to 5 % of the finished part, so the two numbers differ by roughly two orders of magnitude. A masterbatch usually holds 40 to 65 % of the active additive, with a range of 15 to 80 % in extreme cases, and the usual ratio to the base polymer is 1 to 5 %.

The arithmetic follows from the two sourced ranges. A colour masterbatch dosed with 1 to 5 % of a dispersing aid and let down at 1 to 5 % puts 0.01 to 0.25 % of that dispersant into the finished part. That worked example combines the Palsgaard range with the published let-down range and is not a recommendation, since a real formulation sets its own let-down ratio.

Which Dispersing Agent for Which Pigment, Filler and Polymer?#

The dispersant follows the particle rather than the polymer: high-surface-area organic pigments need the most dispersant, carbon black needs a wax matched to its particle size, and mineral fillers at 60 wt% and above need a wax and a metal soap together. The polymer decides the process window and the food-contact route; the particle decides the chemistry and the level.

Table T5. Recommended dispersant type by particle or system, with the level and its basis.

Dispersing agents for colour masterbatch#

Colour masterbatch is where dispersing agents earn their place: the concentrate carries 40 to 65 % pigment, and the dispersant decides how much of that pigment actually contributes to colour strength after the let-down. Pigment locked in an agglomerate is paid for and not used, so the commercial case is made in colour strength before defect rates.

Three chemistries dominate the colour concentrate. Einar 103 is used at 1 to 5 % of the colour masterbatch formulation and covers PE, PP, PVC, PET and PA. Licocene metallocene waxes act as dispersion aid and carrier at once, which suits organic and effect pigments. The metal soaps, calcium stearate and zinc stearate, appear in the same formulations as dispersion aids for pigment wetting, alongside the wax rather than instead of it. Pigment classes and their dosage are on colorants for plastics.

The outcome is measured twice, as colour strength against a reference and as a filter pressure value in bar per gram of pigment.

Dispersing agents for filler masterbatch and highly filled compounds#

Filler masterbatch runs at 70 to 85 % calcium carbonate in a polyethylene or polypropylene carrier, and at that loading the dispersant is what keeps the melt processable at all. Radebe and colleagues worked one loading below that range, at 60 wt% CaCO3 in LLDPE, and found that 3 wt% polyethylene wax with 1.0 wt% zinc stearate brought the melt viscosity back to just above the neat polymer while the filled melt without additives was about three times more viscous. Fischer-Tropsch wax was tested as a drop-in replacement for the PE wax at the same 3 wt% of the concentrate.

Part of the same job is done before the filler reaches the compounder. Stearic acid coatings on calcium carbonate, applied at around 1.1 % on filler weight in a commercial grade, hydrophobise the surface so the polymer wets it more readily and the concentrate needs less dispersant. Oil absorption, in grams of oil per 100 g of filler, predicts that demand across grades, and loading levels per filler are on fillers for plastics.

Dispersing agents for carbon black and pipe compounds#

Black pipe compound is the most demanding dispersion case in commodity plastics: 2 to 2.5 wt% carbon black in the pipe under ISO 4427, delivered as a 35 % masterbatch let down at 5 to 6.5 %, and graded for dispersion on every lot. Those ratios correspond to 19:1 and 14:1, the carrier is an MLDPE or LLDPE below 20 melt index, and Ampacet advises against masterbatches above 40 % carbon black. The 35 % carbon-black concentrate is described on black masterbatch.

Particle size sets both the performance and the difficulty. An N550-type black at 40 to 48 nm generally suffices for pipe, while outdoor service beyond 3 to 5 years calls for N330 types at 26 to 30 nm or N110 below 20 nm, and Ampacet states that finer particles make good dispersion harder. The result is verified per lot on a microdispersion scale of 1 to 5, with 1 best, on about 1.5 mil polyethylene film, while ISO 18553 grades agglomerates on microtome slices. The complete pipe package is on additives for plastic pipes.

What Goes Wrong When Dispersion Fails?#

Dispersion fails for 4 reasons: too little energy in the concentrate, a dispersant that does not wet this pigment, too much dispersant for the system, or a carrier that does not match the base resin. Each produces a different defect and needs a different countermeasure, so the diagnosis comes before the fix.

Specks, gels and filter blockage#

Undispersed agglomerates show up as specks in the part and as a pressure rise at the screen pack, and in film they are counted as gels together with two other causes that need the opposite countermeasure. Ampacet lists 3 sources of gels in polyethylene film, only one of which is a dispersion problem.

• Degraded or crosslinked polymer, driven by high heat, high shear, long residence time and a weak antioxidant package
• Unmelted resin or unmelted concentrate, which passes through the line as a discrete particle
• Poor dispersion caused by insufficient energy applied during concentrate production
• A rising screen-pack pressure, the quantitative form of the same defect, measured as a filter pressure value in bar per gram of pigment

The fixes Ampacet lists pull in opposite directions depending on the source: lower temperatures, higher throughput, a modified screw design, tighter screen packs, smaller masterbatch pellets and a change of carrier resin. Identifying the gel source first is critical, Ampacet states, because lowering the melt temperature cures a degradation gel while aggravating an unmelt. The three gel causes and their opposite fixes are on gels and fisheyes in plastic film.

Plate-out, migration and interaction with other additives#

A dispersant that leaves the melt is a defect: the lowest-molar-mass wax fractions migrate, deposit on dies and rolls and lower the flash point, which is why wax producers strip them out. Mhlabeni reported in 2024 that lower-molar-mass Fischer-Tropsch waxes can worsen die drool relative to polyethylene wax, so the molar-mass distribution of the wax, and not only its class, decides whether the additive stays where it was put. Deposits on rolls and dies are covered on plate-out in PVC processing.

The metal soaps interact with the rest of the formulation rather than with the equipment. Migration of a stearate is the mechanism behind the two Kisuma supplier claims set out above, water carry-over in raffia tape and impaired metallisation and lamination in BOPP. The antioxidant package moves in the other direction, since Espelage and colleagues reported in 2025 that more Irgafos 168 survived compounding in polypropylene when calcium stearate was present, while a 2023 review records a pro-oxidant effect for the same soap under natural exposure. A dispersant change in a stabilised compound is therefore retested rather than assumed neutral.

How Do You Select a Dispersing Agent? 6 Criteria#

Select a dispersing agent in 6 steps, starting with the particle rather than the polymer, because the specific surface area and oil absorption of the pigment or filler set how much dispersant the concentrate needs. The steps run in the order in which their answers constrain one another.

1. Name the particle first, with its specific surface area and its oil absorption in grams of oil per 100 g, because an organic pigment and a mineral filler at the same loading need different chemistries.
2. Decide whether the dispersant also has to be the carrier, since metallocene and micronised polyolefin waxes fill both roles.
3. Match the melting or working temperature to the process window: ethylene bis stearamide melts at 135 to 146 °C, polyethylene wax at 90 to 105 °C and zinc stearate near 120 °C according to Baerlocher.
4. Set the level as a share of the concentrate, then calculate what it becomes after the let-down, because 1 to 5 % of a masterbatch let down at 1 to 5 % leaves 0.01 to 0.25 % in the part.
5. Check the food-contact route for every component, in the EU Union list and the relevant 21 CFR section, before the trial.
6. Check the rest of the formulation for acid scavengers, metallisation and lamination steps and the antioxidant package, since the metal soaps interact with all 3.

The general framework is on how to select plastic additives, while side feeding and screw design are covered on twin-screw compounding of additives.

How Is Dispersion Measured?#

Dispersion is measured in 3 ways: as a filter pressure value in bar per gram of pigment under EN 13900-5, as an agglomerate grade on microtome slices under ISO 18553, and as colour strength against a reference. The filter pressure value is the maximum pressure minus the starting pressure, divided by the mass of pigment that passed the screen. It is obtained by pressing a diluted masterbatch, typically at 8 % pigment in the test compound, through a defined screen pack, for example 14 µm for fibre grades, where values below 1 bar/g are common.

Table T6. Dispersion and appearance test methods for pigments and masterbatch.

Each method sees a different defect. The filter pressure value measures what reaches the screen pack and predicts a fibre or thin-film failure, while ISO 18553 grades what is embedded in a thick wall. Colour strength detects pigment that never contributed to colour, and ASTM D3015 and ISO 11420 are the neighbouring agglomerate methods. The standard numbers here carry no compliance claim for any product, and the full method descriptions are on dispersion testing of pigments and masterbatch.

How Are Dispersing Agents Regulated?#

Dispersing agents are regulated mainly as food-contact additives: the waxes, the amide and the stearates each have their own entry in the Union list of Regulation (EU) No 10/2011, and oxidised polyethylene wax is the only one with a specific migration limit, at 60 mg/kg. Every food-contact grade needs a Union-list entry under EU 10/2011, and where no specific limit applies the generic 60 mg/kg and the overall migration limit of 10 mg/dm² govern instead. Zinc stearate is subject to the zinc limit of 5 mg/kg in Annex II, as amended by Regulation (EU) 2020/1245.

The United States route is a clearance rather than a dosage: ethylene bis stearamide under 21 CFR 178.3860, oxidised polyethylene wax under 21 CFR 177.1620 at a number-average molar mass of at least 1,200, synthetic petroleum wax under 21 CFR 178.3720, polyglycerol esters under 21 CFR 172.854, and the two stearates as GRAS substances. These clearance routes are explained on FDA food contact rules.

Table T7. Regulatory status of the 9 dispersing agents and dispersing aids used in plastics.

Union-list entries were read from the 16 March 2025 consolidation of Regulation (EU) No 10/2011. Fischer-Tropsch wax has no CAS number in our source library and its REACH identifier is unresolved, so no REACH statement is made for it.

No substance in this family is on the REACH Candidate List as of 22 September 2026, and 3 hazard-classification patterns appear in the aggregated notifications.

• Ethylene bis stearamide: not classified by 76.3 % of 1,846 notifiers, a minority notifying H315, H319 and H335.
• Zinc stearate and calcium stearate: zinc stearate not classified by 61.3 % of 2,108 notifiers, with H400 at 30.9 %, H413 at 22.7 % and H335 at 28.3 %; calcium stearate not classified by 85.5 % of 3,808 notifiers.
• Isopropyl triisostearoyl titanate: notified H315, H319 and H335.

Every SML in the Union list is tabulated under specific migration limits, and oxidised polyethylene wax also holds the food-additive number E 914, re-evaluated by EFSA in 2015.

Who Makes Dispersing Agents for Plastics and Masterbatch?#

Dispersing agents come from 3 kinds of producer: wax producers such as Clariant, Sasol and Solstice Advanced Materials, oleochemical companies such as Baerlocher, Peter Greven, PMC Biogenix and Palsgaard, and additive houses such as Struktol that blend and sell ready-made dispersant packages. No single company covers all 5 types, so a masterbatch house typically buys the wax, the soap and the amide from 3 different suppliers.

Table T8. Producers and brand lines recorded for dispersing agents used in plastics.

Companies are listed for the dispersant lines recorded in our source library. No company is ranked, and no company pays for placement.

Grades, sites and certifications are compared in PE wax and polymer wax manufacturers. Our source library holds no market size, growth rate or price for dispersing agents in plastics, so this page states the structure of the supply rather than its value. The soap producers are listed under calcium and zinc stearate manufacturers.

Complete List of Dispersing Agents for Plastics and Masterbatch: 9 Substances#

The complete list below gives the 9 substances in the directory that act as dispersing agents in plastics, with CAS number, type and EU food-contact status, in the order of the 5 types; each is filed under another family, because dispersing is a second job for all of them.

Table T9. All 9 dispersing agents and dispersing aids recorded for plastics.

All 9 substances are filed under the lubricant, antifog or coupling-agent family and are listed here for their dispersing function. Our source library holds no substance record for a polymeric dispersant used in plastics.

Every other additive family is in the plastic additives database, where each substance carries its full identity, dosage and regulatory record.

How Do Dispersing Agents Differ From Lubricants, Coupling Agents and Processing Aids?#

Dispersing agents share the processing-modifier group with 6 other families: lubricants act between melt and metal, processing aids act at the die wall, mold release agents act at the tool, slip and antiblock act on the finished film surface, and desiccants act on water. The overlap with the lubricants is chemical, not editorial: polyethylene wax, oxidised polyethylene wax, ethylene bis stearamide, calcium stearate and zinc stearate are all lubricants in their primary listing and dispersants in this one.

Table T10. The 7 processing-modifier families and the interface each one acts on.

Dispersants in paints, inks and coatings: why they are not plastic additives#

A coatings dispersant works in a liquid vehicle where the pigment can settle over days, so it is formulated for long-term suspension rather than for the seconds of residence time in a twin-screw extruder, and it is outside the scope of this reference. The polymeric wetting and dispersing additives that rank for the same search words, including the DISPERBYK and Anti-Terra lines and equivalents from BASF, Arkema, Borchers and Lubrizol, serve solvent-borne and water-borne systems where flocculation and sedimentation are the failure modes. They are named as context only, and no coatings grade is recommended for a plastics application. Two adjacent phrases also fall outside the border: zinc stearate dispersion and calcium stearate dispersion mean aqueous dispersions of those substances, not dispersing agents. Dispersants for textiles, drilling fluids, construction chemicals and oil spills are separate product classes.

Machine or additive: what the twin-screw extruder does and what the dispersant does#

The extruder supplies the stress and the dispersant lowers the stress that is needed, which is why a dispersion problem is solved either at the screw or at the formulation, and usually at both. Dispersive mixing requires a stress above the cohesive strength of the agglomerate, and that stress comes from the screw geometry, the screw speed and the melt viscosity together. Feeding position is the third lever, since Coperion reports that side-feeding pigments into an established melt gives extremely gentle wetting and avoids agglomerations. The machine side of the same failure appears in the Ampacet gel list, where poor dispersion from insufficient energy during concentrate production is one of the 3 causes of gels in polyethylene film.

Frequently asked questions about dispersing agents for plastics#

Four questions dominate the search results, and two of them exist because the trade uses dispersant, wetting agent and surfactant loosely.

What are examples of dispersing agents?#

The dispersing agents used in plastics are polyethylene wax, oxidised polyethylene wax, Fischer-Tropsch wax, ethylene bis stearamide, calcium stearate, zinc stearate and polyglycerol esters such as Einar 103. Stearic acid belongs to the list in a different role, as a coating applied to calcium carbonate at the filler producer, and isopropyl triisostearoyl titanate is a coupling agent with a dispersant function.

What is the difference between a wetting agent and a dispersing agent?#

A wetting agent only displaces air from the pigment surface, while a dispersing agent also helps break the agglomerate apart and then keeps the freed particles from re-agglomerating. The three steps run in that order, so every dispersing agent is also a wetting agent while the reverse does not hold. A carrier wax adds a fourth role by forming part of the concentrate matrix.

What is a polymer dispersant?#

A polymer dispersant, also sold as a hyperdispersant, carries anchor groups that adsorb on the pigment and polymer chains that keep the particles apart by steric repulsion; this reference holds no verified grade data for polymeric dispersants in plastics yet. The documented polymeric dispersants are coatings products. No dosage, food-contact route or supplier is stated here for a plastics grade, because none is established.

Do dispersing agents affect food-contact compliance?#

Yes: every dispersant in the concentrate has to be authorised for the food-contact application, and oxidised polyethylene wax carries a specific migration limit of 60 mg/kg under Regulation (EU) No 10/2011 while polyethylene wax and ethylene bis stearamide have none. Where no specific limit applies, the generic limit of 60 mg/kg and the overall migration limit of 10 mg/dm² govern the same substance. How an additive reaches the food is explained under additive migration in plastics.