Nucleating Agents: 8 Types, Mechanisms, Dosage and Selection

Nucleating agents are additives that give a semi-crystalline plastic ready-made crystallization sites, so the polymer crystallizes at a higher temperature on cooling and forms more, smaller crystals instead of a few large spherulites, and this reference sorts them into 8 types. They are dosed from 200 ppm to about 1 wt% of the polymer, which raises the practical question: which of the 8 types belongs in which polymer, and at what level? Clarifying agents answer one end of it, as the subclass that raises nucleation density until the crystalline superstructures fall below the wavelength of light.

Nucleation changes 5 things in a moulded part: cycle time falls; stiffness and heat deflection temperature rise, the target of the organophosphate salts ADK STAB NA-11 and NA-21; shrinkage becomes isotropic, the claim of Hyperform HPN-20E; haze falls with a soluble clarifier such as DMDBS or Irgaclear XT 386; and regrind behaves more consistently.

Nucleating agents are one of the 43 families of plastic additives, filed with the property modifiers rather than with the fillers or the stabilizers. This page covers the definition, the boundary against fillers and clarifiers, the three mechanisms, the 8 types in supplier-generation order, what nucleation changes, dosage in ppm and wt%, the nucleator each polymer needs, a 6-step selection route, testing, the EU and US food-contact rules, the producers, and all 21 substances.

The table compares the 8 types of nucleating agents for plastics by example grades, solubility, level and target property.

Levels are research or tested values unless marked as an FDA or EU legal maximum.

What Are Nucleating Agents?#

A nucleating agent is a plastic additive that provides a foreign surface or a self-assembled structure on which a semi-crystalline polymer starts to crystallize, so crystallization begins at a higher temperature during cooling and produces many small crystals instead of a few large ones. It does not work in amorphous plastics such as polystyrene, polycarbonate or PMMA, because there is no crystallization to seed, and it is not a filler, even when a filler such as talc nucleates as a side effect. The polymers that respond are the semi-crystalline ones: industrial polypropylene is 30 to 60 percent crystalline, and polyethylene, polyamides, PET, PLA and PHA all crystallize on cooling, a process also written crystallisation in British usage.

Nucleating agents are a small-tonnage family with a large effect. The ECHA plastic additives mapping exercise lists 5 substances under the function "nucleating agent" among about 418 additives registered above 100 tonnes per year, and the root taxonomy files them as one of 43 families in the property-modifier group.

Why do semi-crystalline plastics need a nucleating agent?#

Polypropylene crystallizes slowly and nucleates almost nothing on its own, so a nucleator is what turns cooling time into cycle time: Milliken reports UL-certified energy savings of 5 to 8 percent for four Hyperform HPN grades in thin-wall lids. The 5 reasons a semi-crystalline plastic receives a nucleating agent are listed below.

• Cycle time and energy: Milliken states more than 10 percent cycle-time reduction and about 15 percent energy saving for Millad NX 8000 against conventional clarifiers, and 10 percent on average for Millad NX 8000 ECO under a UL Environmental Claim Validation.
• Stiffness and heat resistance: ADEKA reports that 0.1 wt% ADK STAB NA-27 lets a part be 10 percent thinner at equal load, about 9 kg per 90 kg of polypropylene in a vehicle.
• Dimensional stability: Hyperform HPN-20E gives balanced, isotropic shrinkage, which removes warpage from caps and closures.
• Transparency: clarified polypropylene is used in more than 22 markets according to Milliken.
• Regrind and recyclate: the Association of Plastic Recyclers rates nucleating agents "Design Preferred" for rigid polypropylene.

Nucleating agents vs clarifying agents: what is the difference?#

Every clarifying agent is a nucleating agent, but only those that dissolve in the melt and rebuild as a nanofibrillar network reach the nucleus density needed to make polypropylene transparent. Kristiansen, Tervoort and Smith at ETH Zürich showed in Macromolecules (2003) that DMDBS in isotactic polypropylene gives its largest rise in crystallization temperature between 0.2 and 1 wt%, with liquid-liquid demixing above 2 wt%, while Horváth and colleagues reported in RSC Advances (2014) that sorbitol clarifiers dissolve in polypropylene only to a few thousand ppm at most.

Particulate nucleators have no such optical route, so a talc-nucleated part stays opaque, and the threshold is measurable: under ASTM D1003-21 a material with more than 30 percent haze counts as diffusing rather than transparent. Grade-by-grade data for every sorbitol, nonitol and trisamide chemistry sit on clarifying agents for plastics (clarifiers).

Is talc a nucleating agent?#

Yes: talc nucleates polypropylene, polyamides and polyesters, and 0.5 to 5 wt% is the level studied for nucleation, while 10 to 40 wt% is filler loading where nucleation is a side effect. Talc (CAS 14807-96-6) is a platy phyllosilicate whose basal surface matches alpha-polypropylene, and its effect in a slow polyester is larger still: 6 wt% talc in PLLA raised the nucleation density about 500-fold and cut the crystallization half-time seven-fold at 100 to 120 °C (Kolstad, in the review of Gao and Masato, UMass Lowell, 2024). Grades, particle sizes and loadings are set out on talc in plastics.

How Do Nucleating Agents Work?#

Nucleating agents work in 3 ways: an insoluble particle offers a surface that matches the polymer lattice, a soluble nucleator dissolves in the melt and rebuilds as nanofibrils on cooling, and a chemical nucleator reacts with the polymer chain ends to create ionic seeds. All three shorten the same step, the formation of a stable nucleus, and the route a grade takes decides its dosage band, its processing window and its interactions.

Particulate nucleators: heterogeneous nucleation and epitaxy#

A particulate nucleator never melts at processing temperature: ADEKA gives a melting point above 400 °C for ADK STAB NA-11, so the particle stays solid in the polypropylene melt and offers its surface to the growing crystal. Heterogeneous nucleation on that surface lowers the free-energy barrier to a stable nucleus, and epitaxy, the lattice matching described by Wittmann and Lotz (1990), explains why one particle selects the alpha form of polypropylene and another the beta form.

Efficiency then depends on the surface available, which makes particle size and dispersion as important as chemistry: Simanke and colleagues (2016) identified poor dispersion as the reason sodium benzoate is outperformed by the third-generation salts. The ADEKA melting points mark where the particulate route ends: ADK STAB NA-27 above 230 °C, NA-21 and NA-71 above 210 °C, NA-902 above 210 °C and NA-960 above 200 °C. Nucleation and crystal growth are explained step by step on polymer crystallization and nucleation.

Soluble nucleators: a self-assembled fibril network#

A soluble nucleator dissolves in the melt and separates out on cooling as a network of nanofibrils, whose surface then nucleates the polymer: for DMDBS in isotactic polypropylene the useful window is 0.2 to 1 wt%, and above 2 wt% the system demixes. That system is monotectic, as Kristiansen, Tervoort and Smith showed at ETH Zürich in Macromolecules (2003). Benzenetrisamides reach the same effect two orders of magnitude lower: Blomenhofer and colleagues at the University of Bayreuth, with Ciba, clarified isotactic polypropylene from a weight fraction of 0.0002, that is 200 ppm, in Macromolecules (2005).

Dissolution temperature is the second design limit, because a clarifier that does not dissolve does not clarify. The three reference values are listed below.

• Traditional sorbitol clarifiers need about 220 °C in polypropylene to dissolve fully.
• MDBS at 0.4 wt% dissolves at about 210 °C, measured by Iwasaki and colleagues (2020).
• Millad NX 8000 dissolves at lower temperatures than traditional clarifiers, which Milliken states comparatively without publishing a figure.

Chemical nucleation in polyesters#

In PET a chemical nucleator works by reacting rather than by presenting a surface: the sodium ion of sodium benzoate attacks the polyester chain ends and leaves ionic end groups that nucleate the crystal, at the cost of some chain scission. Wang and colleagues (2024) describe the sequence, in which the anionic end groups act as the nuclei while the same reaction shortens the chains, so intrinsic viscosity falls as nucleation improves.

The same substance therefore has two mechanisms depending on the polymer: in polypropylene sodium benzoate is a particulate nucleator, in PET a reagent, which is why PET formulators watch intrinsic viscosity and polyolefin formulators watch crystallization temperature.

How nucleating efficiency is measured: Tc, crystallization half-time and the Fillon scale#

Nucleating efficiency is read from three numbers: the peak crystallization temperature on cooling, the isothermal crystallization half-time, and the position on the self-nucleation efficiency scale, where the best commercial polypropylene nucleators reach only 60 to 70 percent. Fillon, Lotz, Thierry and Wittmann at CNRS Strasbourg defined that scale in 1993 by taking the polymer's own crystal fragments as the 100 percent reference. The three metrics are listed below.

• Peak crystallization temperature (Tc) on DSC cooling: the comparative metric for polyolefins, where TMB-5 at 0.6 wt% raises the Tc of PET by 16.6 °C.
• Isothermal crystallization half-time: the working metric for slow polyesters, where LAK-301 at 1 wt% brings the PLA half-time at 140 °C from 61 minutes to 1.8 minutes.
• Nucleation efficiency on the Fillon scale: the normalized measure that caps commercial polypropylene nucleators at 60 to 70 percent.

The cooling programme and the evaluation of these curves are set out on DSC testing: crystallization temperature and nucleation efficiency. No standard number for the DSC crystallization test is established here.

8 Types of Nucleating Agents for Plastics#

The 8 types of nucleating agents for plastics are mineral nucleators, carboxylate salts, organophosphate salts, bicyclic and cyclic dicarboxylate salts, soluble clarifying nucleators, beta-nucleating agents, polyester nucleators and polymeric nucleators. Suppliers still order the particulate types by generation: talc and sodium benzoate first, phosphate esters such as ADK STAB NA-11 second, the Hyperform dicarboxylate salts third. The clarifier line moved the same way, from DBS through MDBS and DMDBS to Millad NX 8000 and the trisamides.

1. Mineral nucleators: talc, boron nitride and other particles#

Mineral nucleators are inorganic particles, above all talc, that nucleate the alpha form of polypropylene and also stiffen the compound. Their platy surfaces give the epitaxial match without any dissolution step, and the same particles double as filler, which makes the loading the deciding question.

Talc (CAS 14807-96-6) is studied at 0.5 to 5 wt% as a nucleator and used at 10 to 40 wt% as a filler, carries EU entry FCM 615 with no specific migration limit (SML) and is cleared in the US under 21 CFR 178.3297. Boron nitride (CAS 10043-11-5) is the standard nucleator for PHA: FDA Food Contact Notification (FCN) 970 covers it up to 1 wt% there, and in the EU it is FCM 583 under group restriction 16 with an SML(T) of 6 mg/kg expressed as boron.

2. Carboxylate salts: sodium benzoate#

Carboxylate salts are the first-generation nucleators, represented by sodium benzoate (CAS 532-32-1), which was identified as one of the best organocarboxylic salts for polypropylene in the 1960s and is still used at 1,000 to 2,200 ppm. The salt stays solid in the polyolefin melt and nucleates epitaxially, like the mineral particles.

Simanke and colleagues (2016) tested it against the third-generation salts at 1,000 to 2,200 ppm in polypropylene, found its efficiency limited by poor dispersion, and recorded a negative interaction with calcium stearate. In the EU it is covered through benzoic acid, FCM 116, under the Annex I rule for salts of authorised acids; in the US it is Generally Recognized As Safe under 21 CFR 184.1733.

3. Organophosphate salts: NA-11 and NA-21#

Organophosphate salts are the second-generation nucleators: aryl phosphate ester salts such as ADK STAB NA-11 that stay solid in the melt, raise the crystallization temperature and heat deflection temperature, and add partial clarity. ADEKA describes the class as heat-resistant, extraction-resistant and odourless.

NA-11 is sodium 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate (CAS 85209-91-2), melting above 400 °C, listed in 21 CFR 178.3295 up to 0.30 wt% and 0.10 wt% for conditions A to H, and in the EU FCM 749 with an SML of 5 mg/kg. NA-21 is a hydroxy aluminium bis phosphate (CAS 151841-65-5) blended with a lithium fatty-acid salt, whose lithium component is essential to the activity (Lin and colleagues, Polymers 2022, 14:3637). Its US limit is 0.25 wt% under 178.3295 and 0.18 wt% under FCN 202; in the EU it is FCM 771, SML 5 mg/kg, with the Annex II limits of 0.6 mg/kg lithium and 1 mg/kg aluminium, and its main component carries the harmonised classification Aquatic Chronic 2, H411 (CLP Annex VI index 013-010-00-5). The NA series is compared grade by grade on phosphate ester nucleating agents.

4. Bicyclic and cyclic dicarboxylate salts: Hyperform HPN#

Bicyclic and cyclic dicarboxylate salts are the third-generation nucleators: Hyperform HPN-68L and HPN-20E, which crystallize polypropylene faster than sodium benzoate or DMDBS at the same 1,000 to 2,200 ppm. Their advantage is kinetic: Simanke and colleagues (2016) compared the three chemistries at identical loadings in the same resin.

HPN-68L is disodium cis-endo-bicyclo[2.2.1]heptane-2,3-dicarboxylate (CAS 351870-33-2), covered by FCN 186 up to 0.25 wt% in PP and HDPE for all foods (A to H) and in LLDPE (B to H); in the EU it is FCM 817, SML 5 mg/kg, purity at least 96 percent, excluded from polyethylene in contact with acidic foods. HPN-20E is about two thirds calcium cis-1,2-cyclohexanedicarboxylate and one third zinc stearate (Sowiński and colleagues, 2015), and its ruler-like particles orient in flow, which produces the isotropic shrinkage the grade is sold for; it is covered by FCN 608 up to 0.25 wt% in all polyolefins and by FCM 816, SML 5 mg/kg, with the zinc share under the Annex II zinc limit of 5 mg/kg. Five manufacturers hold notifications for this chemistry: Milliken since 2006, GCH Technology since 2023, Beijing Jihaichuan since 2024, Zhejiang Sinoview and Jiangsu Jiyi in 2026.

5. Soluble clarifying nucleators: sorbitol, nonitol and trisamide#

Soluble clarifying nucleators are sorbitol acetals, nonitol acetals and benzenetrisamides that dissolve in the melt and rebuild as a nanofibrillar network, which nucleates polypropylene densely enough to make it transparent. The network is the active surface, so the dosage window is bounded at both ends.

DMDBS (Millad 3988, CAS 135861-56-2) works between 0.2 and 1 wt%, Millad NX 8000 (CAS 882073-43-0) is cleared up to 0.5 wt% under FCN 825, and the benzenetrisamide Irgaclear XT 386 (CAS 745070-61-5) is recommended at 150 to 200 ppm with an FDA cap of 250 ppm under FCN 824. Ultra-clear polypropylene historically needed 3,000 to 4,000 ppm of clarifier according to Milliken, against 150 to 200 ppm for a trisamide today. Milliken states 17 times less migration into olive oil for Millad ClearX 9000 than for the market-leading clarifier, normalized and without disclosing that grade's chemistry, and ADEKA reports 2.2 percent haze at 1 mm for ADK TRANSPAREX against a lowest market value of 3.2 percent, third-party verified.

6. Beta-nucleating agents#

Beta-nucleating agents are selective nucleators, such as calcium pimelate, NU-100 and TMB-5, that force polypropylene into its trigonal beta form, which is tougher than the usual alpha form. Selectivity comes from the lattice match rather than the loading, so the effect is strongly concentration-dependent, and Leugering identified gamma-quinacridone as a beta-nucleant in 1967.

Calcium pimelate (CAS 19455-79-9) is studied at 0.2 wt%, is the subject of FCN 793 up to 0.15 wt% and appears as FCM 820, pimelic acid and salts, with no SML. NU-100, N,N'-dicyclohexyl-2,6-naphthalenedicarboxamide (CAS 153250-52-3), is covered by FCN 713 up to 0.2 wt% and by FCM 772, SML 5 mg/kg. TMB-5, N,N'-dicyclohexylterephthalamide (CAS 15088-29-6), has no EU Union list entry and no FCN in our source library, so no food-contact level can be stated; at 0.025 to 0.05 wt% in rotation-sheared PP pipe it gave a tensile strength of 40.98 MPa against 33.62 MPa without shear (Abudurezhake and colleagues, 2024). Pipe practice combines 0.02 percent alpha with 0.2 percent beta nucleator. Beta content, pipe and microporous film uses are covered on beta nucleating agents.

7. Nucleators for polyesters: PLA, PET and PHA#

Polyester nucleators are sulfonate, carboxylate and amide compounds that attack the slow crystallization of PLA and PET, where the working metric is the crystallization half-time rather than the crystallization temperature. A neat polyester takes tens of minutes to crystallize, so the additive makes a moulding cycle possible at all.

For PLA the reference grade is LAK-301, potassium dimethyl 5-sulfoisophthalate (CAS 10433-41-7, Takemoto Oil & Fat): at 0.25 wt% it raised crystallinity from 10 percent to 45 percent, and at 1 wt% it cut the half-time at 140 °C from 61 minutes to 1.8 minutes (Nagarajan, Mohanty and Misra, University of Guelph, 2016). Orotic acid (CAS 65-86-1) at 1 wt% raised PLA crystallinity from 26 percent to 63 percent at 80 °C (Gao, Masato and colleagues, 2022), TMC-328 at 0.2 wt% cut the half-time from 4.1 to 1.8 minutes, and EBH is cleared up to 1 wt% under FCN 1257, while zinc phenylphosphonate (CAS 34335-10-9) is a PLA nucleator whose dosage is not published here. For PET, sodium saccharin is cleared up to 0.1 wt% under FCN 1148 and TMB-5 at 0.6 wt% raises the crystallization temperature by 16.6 °C; for PHA, boron nitride is cleared up to 1 wt% under FCN 970. LAK-301 is not on the EU Union list as an additive, and FCM 471 and FCM 823 are monomer entries, not a clearance for it.

8. Polymeric nucleators and self-nucleation#

Polymeric nucleators are polymers that crystallize before the matrix does, such as polyvinylcyclohexane in polypropylene and the PLLA/PDLA stereocomplex in PLA, so no small migrating molecule is added at all. The higher-melting polymer crystallizes first and acts as the substrate for the matrix.

Polyvinylcyclohexane (CAS 25498-06-0) is one of the 8 substances listed in 21 CFR 178.3295, at up to 0.1 wt% of the olefin polymer. In PLA the stereocomplex route uses the polymer's own enantiomer: a 99/1 PLLA/PDLA blend with 1 wt% talc cut the crystallization half-time at 110 °C from 25 minutes to 0.4 minutes. Self-nucleation by the polymer's own crystal fragments needs no additive and is the 100 percent reference point of the Fillon scale.

What Does a Nucleating Agent Change? Cycle Time, Stiffness, Haze and Warpage#

A nucleating agent changes 5 things in a semi-crystalline plastic: how fast it solidifies, how stiff and heat-resistant it is, how evenly it shrinks, how clear it is, and how well a coloured or recycled grade holds its shape. All five follow from one physical change, a crystallization exotherm that moves to a higher temperature on cooling, so the part reaches ejection stiffness earlier and builds a finer crystal structure.

Cycle time is the effect that pays for the additive, and every supplier number carries its reference case: Milliken reports UL-certified energy savings of 5 to 8 percent for four Hyperform HPN grades in thin-wall lids, and more than 10 percent cycle-time reduction for Millad NX 8000 against conventional clarifiers. The rest of the moulding package is covered on additives for injection molding.

The same physics works against the formulator when nucleation is unintended: phthalocyanine pigments nucleate polypropylene more strongly than quinacridones and raise shrinkage from 13.6 percent to 22.3 percent, which shows up as warpage in coloured parts.

How Much Nucleating Agent Does a Plastic Need? Dosage in ppm and wt%#

Nucleating agents are dosed between 150 ppm and about 1 wt%: benzenetrisamides clarify polypropylene from 200 ppm, sorbitol clarifiers work between 0.2 and 1 wt%, and particulate nucleators are usually tested at 1,000 to 2,200 ppm. The table separates the three number families, because only the first is a formulation instruction.

Units carry their base. A ppm figure means parts per million of the compound by weight, and 1,000 ppm equals 0.1 wt%, so the 1,000 to 2,200 ppm band of the particulate types is 0.1 to 0.22 wt%. Polyolefins and polyesters are dosed in ppm and wt%, while PVC and rubber use parts per hundred resin; the conversions between ppm, wt% and PHR (parts per hundred resin) follow from those bases. FDA and EU percentages in the table are legal maxima, never recommended levels, and levels for every family are collected on additive dosage levels in plastics.

Most nucleators reach the machine diluted, because powders at 150 to 2,200 ppm cannot be dosed accurately at the throat of a moulding machine, so the grade is normally supplied or pre-compounded as an additive masterbatch. Kisuma's Setogem RD combines nucleation and acid scavenging at 200 to 300 ppm in polypropylene.

Which Nucleating Agent for Which Polymer?#

Each polymer needs a different nucleator because the problem differs: polypropylene nucleates almost nothing on its own, polyethylene already crystallizes fast and needs help with warpage and clarity, and PET and PLA crystallize so slowly that the target is the crystallization half-time. Polyamides sit in a fourth position, where nucleation is bought for injection-moulding cycle time. The matrix pairs each polymer with the types that work in it and their level.

Nucleating agents for polypropylene#

Polypropylene is the polymer that nucleation was built for: Hyperform HPN-68L, HPN-20E, ADK STAB NA-11 and sodium benzoate are all dosed in the 1,000 to 2,200 ppm range, and only the sorbitol and trisamide clarifiers also deliver transparency. The choice inside that range is a choice of target property: the four particulate grades differ less in how much crystallization they produce than in what they do to shrinkage, stiffness and clarity.

Three volume applications carry the family: thin-wall packaging buys cycle time, thermoforming sheet buys stiffness at lower gauge, and automotive downgauging buys the thinner wall ADEKA quantifies at 10 percent with 0.1 wt% ADK STAB NA-27. Grade-by-grade data and thin-wall settings are on nucleating agents for polypropylene.

Clarified polypropylene is a separate decision, built on random copolymer as its usual base.

The nucleator never travels alone. A polypropylene package normally holds a phenolic antioxidant with a phosphite, a thioester, an acid scavenger, hindered amine light stabilizers and a UV absorber outdoors, antistatic agents, slip and antiblock additives, fillers and impact modifiers. The rest of that package is set out on additives for polypropylene.

Nucleating agents for polyethylene#

Polyethylene crystallizes quickly on its own, so nucleation in HDPE and LLDPE is used for warpage in caps and closures, for stiffness in thin-wall containers and for clarity, not for crystallization speed. Seven, Cogen and Gilchrist at Dow and Lehigh University reviewed the HDPE case in Polymer Engineering and Science (2016).

The cleared grades follow from that. Hyperform HPN-68L is covered for HDPE (A to H) and LLDPE (B to H) at up to 0.25 wt% by FCN 186, Hyperform HPN-20E covers all polyolefins at up to 0.25 wt% under FCN 608, and EDBS is cleared in LLDPE and LDPE at up to 0.2 wt% under FCN 509. HPN-210M is the dedicated polyethylene grade, whose main component is sodium 4-[(4-chlorobenzoyl)amino]benzoate (CAS 1489170-67-3), cleared up to 0.25 wt% in polyolefins (B to H) by FCN 1579. HDPE and LLDPE grades are compared on nucleating agents for polyethylene.

One EU restriction is specific to this polymer: the FCM 817 entry for the HPN-68L salt excludes it from polyethylene in contact with acidic foods, so a grade unrestricted in polypropylene needs a food-type check in a PE closure. Warpage control in caps and closures is covered on additives for caps and closures.

Nucleating agents for PET and PLA#

PET and PLA are the two polymers where nucleation decides whether the part survives heat at all: neat PLA needs tens of minutes to crystallize, and 1 wt% LAK-301 brings the crystallization half-time at 140 °C down from 61 minutes to 1.8 minutes. Nagarajan, Mohanty and Misra at the University of Guelph published that result in 2016.

PET takes two routes. Chemical nucleation by sodium benzoate works on the chain ends and costs intrinsic viscosity, while amide nucleators work on the surface: TMB-5 at 0.6 wt% raises the crystallization temperature by 16.6 °C, and sodium saccharin is cleared up to 0.1 wt% under FCN 1148. CPET trays and recycled PET are covered on nucleating agents for PET.

PLA has the larger toolbox, because its crystallization is the slower of the two. LAK-301 at 0.25 wt% raised crystallinity from 10 percent to 45 percent, orotic acid at 1 wt% from 26 percent to 63 percent at 80 °C, TMC-328 at 0.2 wt% cut the half-time from 4.1 to 1.8 minutes, and EBH is cleared up to 1 wt% under FCN 1257.

The nucleator alone is not enough in PLA. Heat resistance needs a hot mould or a post-moulding anneal as well, because the polymer has to stay in its crystallization window long enough to use the nuclei. Mould temperature and annealing schedules are covered on nucleating agents for PLA.

Nucleating agents for polyamides and recycled polyolefins#

Polyamides and recycled polyolefins use nucleation for two different reasons: PA6 and PA66 for cycle time in injection moulding, and recycled polypropylene for the stiffness and shrinkage consistency that a mixed feedstock loses. In polyamides the established products are talc and BRUGGOLEN P22 from Brüggemann, which the supplier describes as reducing injection-moulding cycle time; no dosage for it is established in our source library. PA6 and PA66 cycle times are covered on nucleating agents for nylon.

Recycled polyolefins are the growth case. Nucleators and clarifiers restore in post-consumer recycled polypropylene the stiffness and shrinkage behaviour that a variable feedstock loses, and the Association of Plastic Recyclers design guide rates nucleating agents "Design Preferred" for rigid polypropylene. Data for PCR-PP are collected on nucleating agents for recycled plastics.

Colour is the complication in both cases, because a recycled or pigmented grade already contains particles that nucleate. How additive choices affect sorting and reprocessing is set out on design for recycling.

How Do You Select a Nucleating Agent? 6 Criteria#

Select a nucleating agent in 6 steps: name the target property, confirm the polymer and the crystal form you want, match the type to the melt temperature, check the food-contact route, check the rest of the additive package, then set the level in ppm and confirm it by DSC. Each step removes candidates the next step would otherwise have to test.

1. Name the target property: cycle time, stiffness and heat deflection temperature, clarity, low warpage, or toughness. One nucleator rarely maximises two at once.
2. Confirm that the polymer is semi-crystalline and decide the polymorph. Alpha nucleators raise stiffness and HDT in polypropylene; beta nucleators raise toughness and open the route to microporous film.
3. Match the type to the processing temperature. ADK STAB NA-11, melting above 400 °C, survives any polyolefin melt, while sorbitol clarifiers need about 220 °C to dissolve.
4. Check the food-contact route: the EU FCM number and its SML, a listing in 21 CFR 178.3295 or an FCN, and whether infant contact is included.
5. Check the rest of the additive package for antagonism, above all the acid scavenger and the pigments.
6. Set the level in ppm, then confirm it by DSC and haze measurement and check the dispersion.

Two limits belong in the expectation: commercial polypropylene nucleators reach only 60 to 70 percent on the Fillon scale, and the percentages in 21 CFR 178.3295 are ceilings, so a formulation at the cap is over-dosed. The general framework across all 43 families is on how to select plastic additives.

Dispersion decides whether the chosen level performs, because an agglomerated nucleator presents a fraction of its surface and a clarifier below its dissolution temperature leaves powder in the part. Feeding, melt temperature and screw configuration are covered on plastic compounding.

Which additives conflict with a nucleating agent?#

The acid scavenger is the first additive to check against a nucleating agent: calcium stearate and sodium benzoate interact negatively at the levels where both are used, which is why hydrotalcite or zinc stearate is the safer neutralizer in a nucleated polypropylene. Simanke and colleagues (2016) recorded it at the 1,000 to 2,200 ppm band, against acid-scavenger levels of 0.05 to 0.20 percent in polyolefins. The choice between the neutralizers is set out on acid scavengers and catalyst neutralizers. The 4 antagonism pairs are listed below.

• Sodium benzoate and calcium stearate: a negative interaction at the levels where both are present (Simanke and colleagues, 2016).
• Sodium benzoate and hydrotalcite as the alternative neutralizer: the route that avoids the stearate interaction without giving up acid scavenging.
• Hyperform HPN-20E and a separately added acid scavenger: the grade already carries about one third zinc stearate, and that share counts against the Annex II zinc limit of 5 mg/kg.
• Phthalocyanine pigments and any alpha nucleator: the pigment nucleates as well, and the combined effect raises polypropylene shrinkage from 13.6 percent to 22.3 percent.

Kisuma's quintinite nucleator, the subject of FCN 2476 of 12 February 2026 at up to 2,000 ppm in polyolefins, removes the interaction by nucleating and scavenging acid in one particle. Where the classic package is kept, the full profile of calcium stearate covers its other roles.

Pigments deserve the same scrutiny, because gamma-quinacridone is itself a beta-nucleant, so a colour change can move the crystal form as well as the shrinkage. Pigment classes and their nucleating behaviour are on colorants for plastics, and warpage, plate-out and odour cases are collected on troubleshooting additive-related defects.

How Is Nucleation Tested?#

Nucleation is tested on four properties: the crystallization temperature and half-time by DSC, haze and clarity by ASTM D1003, the heat deflection temperature by ASTM D648 or ISO 75, and impact strength where a beta-nucleator is used. A nucleator that improves one does not automatically improve the others, so the test set follows the target property named in step 1 of the selection route.

One standards trap runs through the optical row. ASTM D1003 is not equivalent to ISO 14782 or ISO 13468-1, so a haze value quoted against the wrong standard cannot be compared with a supplier figure. All methods are indexed under testing plastic additives.

How Are Nucleating Agents Regulated?#

Nucleating agents are regulated first as food-contact additives: the EU authorises them by name in Annex I of Regulation (EU) No 10/2011 with a specific migration limit, and the US either lists them in 21 CFR 178.3295 or clears them through a Food Contact Notification. No other regime restricts the family as a whole.

The REACH picture is correspondingly quiet. No nucleating or clarifying agent in this family appears on the SVHC Candidate List, in REACH Annex XIV or in Annex XVII as of the September 2026 check, and the registrations are few: 52 active dossiers for sodium benzoate and 15 for talc, against 3 for ADK STAB NA-11 and 1 each for Millad NX 8000, Irgaclear XT 386 and LAK-301. For Hyperform HPN-68L, Hyperform HPN-20E, NU-100, RiKACLEAR PC1 and TMB-5, no active registration was found under their CAS or EC numbers in ECHA CHEM in September 2026. Most sorbitol clarifiers, Millad NX 8000, Irgaclear XT 386 and the two Hyperform grades are not classified in the C&L notifications; ADK STAB NA-11 carries self-classifications H332 and H411.

Food contact: EU 10/2011 SMLs, 21 CFR 178.3295 and FCNs#

A nucleating agent is cleared for food contact in the EU only if it appears in Annex I of Regulation (EU) No 10/2011, where the common limit for this family is a specific migration limit of 5 mg/kg. The Union list and the migration testing behind it are explained on EU 10/2011. Every value in the table is a specific migration limits (SML) entry from Annex I, checked against the consolidated text of 16 March 2025, with the Annex II metal limits applied where the substance carries lithium, aluminium or zinc.

EU entries checked against the consolidated text of 16 March 2025; later amendments were not checked.

The US route splits in two. How 21 CFR parts 174 to 178 fit together is set out on FDA food contact rules; 21 CFR 178.3295, "Clarifying agents for polymers", lists 8 substances anyone may use within the stated caps: the NA-21 aluminium salt at 0.25 percent, EDBS at 0.35 percent, MDBS at 0.32 percent, DBS at 0.25 percent, DMDBS at 0.4 percent, polyvinylcyclohexane at 0.1 percent, sodium di(p-tert-butylphenyl)phosphate at 0.35 phr and NA-11 at 0.30 percent or 0.10 percent for A to H. No nucleating agent is "FDA approved": it is either listed in the regulation or the subject of a notification.

A Food Contact Notification binds only its holder. FCN 186, 608, 713, 793, 824, 825, 860, 970, 1148, 1257, 1579, 2095, 2211, 2344, 2357, 2369, 2440, 2476, 2483 and 2495 all cover nucleating or clarifying uses, and the newer ones show two trends: infant-contact exclusions are routine, with FCN 2211 for infant formula and FCN 2440 for repeat-use baby bottles as the exceptions, and four Chinese and Japanese notifiers have entered the HPN-20E chemistry since 2023. Why an FCN binds only its notifier is explained on FDA Food Contact Notifications (FCN).

Talc under the EU classification review#

Talc is the one nucleating agent with a pending hazard classification: the ECHA Committee for Risk Assessment adopted an opinion on 20 September 2024 recommending Carc. 1B and STOT RE 1, but talc still has no entry in CLP Annex VI in the 1 July 2026 consolidation. That recommendation, reported through a supplier source rather than verified against the ECHA record, covers H350 for carcinogenicity and H372 for repeated-exposure lung damage by inhalation. Until an adaptation to technical progress adds the entry, no harmonised classification applies and the proposal cannot be quoted as one in force. How a RAC opinion becomes an Annex VI entry is explained on CLP classification of plastic additives.

Two other assessments already exist. The International Agency for Research on Cancer classified talc not containing asbestos in Group 2A in 2024 and talc containing asbestos in Group 1, while only talc containing asbestiform fibres is listed under California Proposition 65, since 1 April 1990. Milliken markets "talc-free nucleation" on that basis, which is a positioning claim rather than a regulatory statement.

Who Makes Nucleating Agents? Suppliers and Market#

Nucleating agents come from a short list of producers: Milliken, ADEKA, BASF, New Japan Chemical and Takemoto in the established segment, plus GCH Technology, Beijing Jihaichuan, Zhejiang Sinoview and Jiangsu Jiyi, which have taken US food-contact notifications for HPN-20E-type grades since 2023. No independent market size, growth rate or price for nucleating agents is published in our sources, so this section names producers and brand lines rather than a market figure.

Grades, sites and certifications are compared in nucleating and clarifying agent suppliers.

Two structural facts describe the segment. Milliken states that it invented polypropylene clarifying agents nearly 45 years ago and raised Millad capacity by 50 percent at its Blacksburg plant, which puts the clarifier business at the mature end; four new notifiers for one third-generation chemistry in three years is the signature of commoditization. Where these producers sit in the wider additive industry is on largest plastic additive companies.

Complete List of Nucleating and Clarifying Agents: 21 Substances#

The complete list below gives the 21 nucleating and clarifying agents in the directory with CAS number, type, EU food-contact entry and US limit, in the order of the 8 types. Each row is the entry point to that substance's own page, where the identity data, dosage evidence and regulatory history sit in full.

Gamma-quinacridone, Pigment Violet 19, is a beta-nucleant as well as a pigment and is documented with the colorants. Every other additive family is in the plastic additives database.

How Do Nucleating Agents Differ from Fillers, Clarifiers and Foam Cell Nucleators?#

A nucleating agent seeds polymer crystals, a filler replaces polymer volume, a clarifying agent is the nucleator subclass that also removes haze, and a foam cell nucleator seeds gas bubbles rather than crystals. The four families share vocabulary and, in two cases, substances, which is why a datasheet that says "nucleating agent" has to be read together with its loading. In the root taxonomy the separation is clean: property modifiers, fillers and reinforcements, and functional additives.

Foam cell nucleation: the same word, a different job#

A foam cell nucleator seeds gas bubbles, not crystals, and the same trisamide that clarifies polypropylene at 150 to 200 ppm has been studied at 0.1 to 0.5 wt% for cell nucleation in XPS foam. Aksit and colleagues (2019) reported that XPS work with Irgaclear XT 386, one order of magnitude above its clarifying dose.

The physics diverges at the first step. Crystal nucleation needs a surface whose lattice matches the polymer unit cell, while cell nucleation needs a site where dissolved gas leaves solution at lower energy, so surface energy and particle geometry dominate instead.

Nucleating agents outside plastics: glass-ceramics and ice nucleation#

The term nucleating agent is also used in glass-ceramics and in ice nucleation for snowmaking and cloud seeding, and neither is covered here: this reference covers additives used in plastics. Those are different fields with different materials and regulations, and everything on this page concerns semi-crystalline polymers only.

Frequently asked questions about nucleating agents#

The 4 questions below are the ones formulators and buyers ask most often about nucleating agents: what the additive does, how nucleation relates to crystallization, whether it raises crystallinity or only the rate, and what the US status of Millad 3988 is.

What does a nucleating agent do?#

A nucleating agent makes a semi-crystalline plastic crystallize sooner and finer: crystallization starts at a higher temperature during cooling, the part sets faster, and the many small crystals leave the plastic stiffer, more heat-resistant and, with a clarifier, clearer. Shrinkage also becomes more even, which removes warpage from thin-wall parts and closures.

Is nucleation the same as crystallization?#

No: nucleation is the first step of crystallization, in which a stable nucleus forms, and crystal growth is the second step, in which chains add to that nucleus. A nucleating agent acts only on the first step, by lowering the energy barrier to that nucleus. The resulting spherulite is the structure a nucleator makes smaller and more numerous, and its size decides stiffness and light scattering.

Does a nucleating agent raise crystallinity or only the crystallization rate?#

Both, but not equally: in polypropylene a nucleator mainly raises the rate and the temperature of crystallization, while in a slow-crystallizing polyester it also raises the degree of crystallinity, from 26 percent to 63 percent for PLA with 1 wt% orotic acid. Industrial polypropylene is 30 to 60 percent crystalline with or without a nucleator, so the additive moves the kinetics rather than the final structure. The definition and measurement of crystallinity set the limits of that effect.

Is Millad 3988 FDA approved?#

Millad 3988 (DMDBS) is cleared, not approved: 21 CFR 178.3295 allows it in olefin polymers with at least 85 percent propylene units at up to 0.4 wt%, under conditions of use A to H. The FDA lists substances for uses rather than approving products, and 0.4 wt% is a legal ceiling: the level that clarifies is 0.2 to 1 wt%. In the EU it is FCM 766 with no SML.