Nucleating Agents for Polypropylene: 8 Nucleator Classes, Dosage and Selection

Nucleating agents for polypropylene are additives that give the melt ready-made crystallization sites, so that PP starts to crystallize at a higher temperature and forms more, smaller spherulites, at levels between 150 ppm and about 1 wt% for organic nucleators and 0.5-5 wt% for talc. Isotactic polypropylene (also PP crystallisation, in British spelling) grows crystals slowly and nucleates almost nothing by itself, which is why Gahleitner and co-workers at Borealis (International Polymer Processing 26, 2011) call it an ideal material for controlled nucleation, so which nucleator suits which PP part?

Nucleators sit in the small group of plastic additives that change how a polymer solidifies rather than how it resists heat, light or fire: a nucleator decides cycle time, stiffness, shrinkage and, for the clarifier subclass, whether the part is see-through.

This page covers the 8 nucleator and clarifier classes used in PP, the nucleator-versus-clarifier and alpha-versus-beta choices, dosage by application from thin-wall packaging to pipe, additive interactions, DSC and haze testing, EU and US food-contact status, and the producers that supply them.

Key figures

• 8 nucleator classes are used in polypropylene, from organophosphate salts to beta nucleators
• Benzenetrisamide clarifiers work at 150-200 ppm, the lowest dose of any class covered here
• FDA caps Hyperform HPN-68L and HPN-20E at 0.25 wt% each in polyolefins (FCN 186, FCN 608)
• The EU specific migration limit is 5 mg/kg for NA-11, HPN-68L, HPN-20E, Millad NX 8000 and Irgaclear XT 386 alike

Why Does Polypropylene Need Nucleating Agents?#

Polypropylene needs nucleating agents because isotactic PP crystallizes slowly at large undercooling and nucleates almost no crystals by itself, so the resin sets late in the mould, in coarse spherulites that scatter light and leave the part more flexible than stiff. Homopolymer iPP melts between 160 °C and 166 °C, reaches only 30-60 % crystallinity and has a density of 0.895-0.93 g/cm3, a range wide enough that two PP parts from the same resin can differ in stiffness purely because one cooled through a nucleated path and the other did not. The hub on nucleating agents covers the same 8 classes across every semicrystalline polymer that needs them.

How does polypropylene crystallize without a nucleating agent?#

Unnucleated polypropylene crystallizes by sporadic nucleation at large undercooling: the melt cools well below its melting range before the first nuclei appear, each nucleus then grows into a large spherulite, and the part reaches dimensional stability late. The process runs in 3 steps.

1. The melt cools below its equilibrium melting point without crystallizing, since iPP has almost no heterogeneous nuclei of its own.
2. Sporadic nucleation begins only at a large undercooling, when a handful of stable nuclei form from chance chain folding.
3. Each nucleus grows into a spherulite, and because so few nuclei exist, every spherulite grows large before meeting its neighbours, giving unnucleated PP its coarse, light-scattering microstructure.

A nucleating agent shortens this sequence by supplying a surface or a self-assembled structure the melt nucleates on directly, so crystallization starts higher and produces more, smaller spherulites. Epitaxy, the lattice matching between a nucleator's surface and the PP helix, explains why some nucleators select the alpha form and others the beta form (Wittmann and Lotz, Progress in Polymer Science 15, 1990). Tc, the peak of the DSC cooling exotherm at 10 °C/min, is the quick metric of nucleator performance. Spherulite growth and undercooling are explained further under polymer crystallization and nucleation.

What does a nucleating agent change in a polypropylene part?#

A nucleating agent changes six things in a polypropylene part: the crystallization temperature rises, the cycle time falls, flexural modulus and heat deflection temperature rise, shrinkage becomes more isotropic, warpage falls and, at high enough nucleus density, haze falls. Milliken states that 4 Hyperform HPN grades deliver UL-validated energy savings of 5-8 % in thin-wall lids and a cycle-time cut of more than 10 % for Millad NX 8000; ADEKA reports that 0.1 wt% of NA-27 lets a part be made 10 % thinner at the same load, about 9 kg less material per 90 kg of PP per vehicle.

Table 1. What a nucleating agent changes in a PP part

No figure in our source library states a numeric Tc rise or flexural-modulus gain beyond the two supplier claims above. Nucleation raises stiffness at the cost of impact strength, a trade-off the Madison Group also names, and the heat deflection temperature gain follows the same load and deflection conventions used across every other additive family on this site.

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

A nucleating agent mainly changes when and how polypropylene crystallizes, not how much of it crystallizes: it raises the crystallization temperature and multiplies the number of spherulites, while the final degree of crystallinity moves far less. More nuclei mean smaller spherulites at roughly the same crystalline fraction, since nucleation density, not total crystallinity, is what a nucleator primarily controls. On the Fillon self-nucleation efficiency scale, NE = (Tc,NA − Tc,1) / (Tc,2max − Tc,1) × 100 %, commercial iPP nucleators reach at best 60-70 % efficiency (Benoit Fillon, Bernard Lotz, Rene Thierry and Jean-Claude Wittmann, University of Strasbourg, Journal of Polymer Science Part B 31, 1993).

What Are the 8 Types of Nucleating Agents for Polypropylene?#

The 8 types of nucleating agents used in polypropylene are organophosphate salts, bicyclic and cyclic dicarboxylate salts, carboxylate salts, talc and other mineral nucleators, sorbitol and nonitol clarifiers, trisamides, polymeric nucleators and beta nucleating agents, with the first two classes carrying most of the commercial volume. The list is ordered by commercial importance in PP, particulate alpha-nucleators first and beta nucleators last, and every later list and table on this page repeats that same order.

Table 2. The 8 nucleator classes used in PP

Supplier literature also describes these classes by generation: sodium benzoate and talc as first-generation, phosphate esters such as NA-11 as second-generation, and bicyclic dicarboxylates such as HPN-68L as third-generation; on the clarifier side the same language runs DBS, then MDBS, then DMDBS, then nonitol acetals such as Millad NX 8000, then trisamides as the lowest-dose generation yet.

1. Organophosphate salts (NA-11, NA-21, NA-27)#

Organophosphate salts such as ADK STAB NA-11 (CAS 85209-91-2) are insoluble particulate nucleators that melt above 400 °C, so they stay solid throughout processing and offer their surface as a permanent crystallization site. ADEKA describes NA-11 as raising stiffness, HDT, Tc and clarity, and as heat- and extraction-resistant and odourless. It carries EU FCM 749 at SML 5 mg/kg, and 178.3295 caps it at 0.30 wt% (0.10 wt% conditions A-H); ADEKA publishes no dosage, so the FDA figure is a legal maximum only. Full identity sits on NA-11.

NA-21 (CAS 151841-65-5) is the hydroxy aluminium bis-phosphate version, blended with a lithium fatty-acid salt that Lin and co-workers (Polymers 14, 2022, 3637) found essential to its activity. It carries EU FCM 771 at SML 5 mg/kg, plus Annex II limits of 0.6 mg/kg lithium and 1 mg/kg aluminium, and a harmonised Aquatic Chronic 2, H411 classification. FDA 178.3295 caps it at 0.25 wt%, FCN 202 at 0.18 wt%. ADEKA reports that 0.1 wt% of NA-27 (melting above 230 °C) lets a part be made 10 % thinner at equal load, about 9 kg less material per 90 kg of PP per vehicle. The class of phosphate ester nucleating agents is compared on its own page.

2. Bicyclic and cyclic dicarboxylate salts (Hyperform HPN-68L, HPN-20E)#

Bicyclic and cyclic dicarboxylate salts are the third-generation particulate nucleators for polypropylene, and the two commercial references are Hyperform HPN-68L (CAS 351870-33-2) for crystallization speed and Hyperform HPN-20E (CAS 491589-22-1) for isotropic shrinkage. Simanke and co-workers (2016) found that HPN-68L at 1,000-2,200 ppm accelerates PP crystallization more efficiently than sodium benzoate or DMDBS. FDA FCN 186 caps it at 0.25 wt% in PP and HDPE (conditions A-H) and LLDPE (B-H); the EU lists it as FCM 817 at SML 5 mg/kg, minimum purity 96 %, not for use with PE in acidic foods. Full FCN 186 conditions sit on Hyperform HPN-68L.

HPN-20E is formulated as roughly two-thirds calcium cis-1,2-cyclohexanedicarboxylate and one-third zinc stearate (Sowiński and co-workers, 2015); its ruler-like particles orient in flow to balance shrinkage between the flow and cross-flow directions. FDA FCN 608 caps it at 0.25 wt% in all polyolefins, and the EU lists it as FCM 816 at SML 5 mg/kg, with the Annex II zinc SML of 5 mg/kg on its stearate share. Hyperform HPN-20E is the warpage grade, and 4 more suppliers now hold FCNs for the same chemistry.

3. Carboxylate salts (sodium benzoate and aluminium benzoates)#

Sodium benzoate (CAS 532-32-1) is the first-generation nucleator for polypropylene and still the cheapest, but its poor dispersion and its antagonism with calcium stearate keep it out of demanding compounds. Harold N. Beck at Dow identified it, together with basic aluminium dibenzoate, as one of the best nucleators in the first systematic screening of PP nucleators, published in the Journal of Applied Polymer Science in 1967. Simanke and co-workers tested it at the same 1,000-2,200 ppm range used for HPN-68L in 2016 and confirmed the negative interaction with calcium stearate at that loading. In the EU it is covered through benzoic acid (FCM 116) and the Annex I salt rule, since sodium carries no metal SML of its own; in the US it is GRAS under 21 CFR 184.1733. Dispersion problems and the calcium stearate antagonism are detailed on sodium benzoate.

4. Talc and mineral nucleators#

Talc is the mineral nucleator for polypropylene: it nucleates the alpha form at 0.5-5 wt% and keeps nucleating as a side effect when it is used as a 10-40 wt% reinforcing filler. Talc (CAS 14807-96-6) accounted for 32 % of US talc sales by end use in 2024 (US Geological Survey), plastics being the largest single market. The EU lists it as FCM 615 with no SML, and the US permits it under 21 CFR 178.3297 as a colorant for polymers. Because talc adsorbs antioxidants from the melt, talc-filled PP needs a stronger stabilizer package than an unfilled grade. Grades and loadings are on talc in plastics; the classification history below sits on talc.

5. Sorbitol and nonitol clarifiers (DMDBS, MDBS, NX 8000)#

Sorbitol and nonitol clarifiers such as DMDBS (Millad 3988, CAS 135861-56-2) work differently from every particulate nucleator: they dissolve in the polypropylene melt and crystallize on cooling into a nanofibrillar network whose surface nucleates PP at ultrahigh density. That mechanism, described by Kristiansen, Tervoort, Smith and Bernland at ETH Zürich, gives crystallites too small to scatter visible light, so the part turns see-through. The iPP/DMDBS system is monotectic: Kristiansen and co-workers (Macromolecules 36, 2003, 5150) found the maximum Tc gain and lowest haze inside a 0.2-1 wt% window, with optics worsening above 1 wt% and demixing above 2 wt%.

Sorbitol clarifiers dissolve in PP only to a few thousand ppm at most (Horváth and co-workers, 2014). Traditional grades need about 220 °C to dissolve, 0.4 wt% MDBS dissolves at about 210 °C (Iwasaki, 2020), and Millad NX 8000 dissolves lower still, which Milliken states widens the processing window. Every generation of clarifying agents for plastics is compared on the clarifier hub; the phase diagram behind the 0.2-1 wt% window of DMDBS (Millad 3988) is on its own page.

6. Trisamide nucleators and clarifiers#

Trisamides are the lowest-dose nucleators used in polypropylene: Blomenhofer, Schmidt and co-workers at the University of Bayreuth, with Ciba and ETH Zürich, showed in Macromolecules 38 (2005) 3688 that substituted 1,3,5-benzenetrisamides clarify isotactic PP at weight fractions as low as 0.0002, which is 200 ppm. Small structural changes switch a trisamide between alpha, beta and mixed nucleation. Irgaclear XT 386 (CAS 745070-61-5) is recommended at 150-200 ppm (Ciba, 2008), carries an FDA cap of 250 ppm under FCN 824, and is listed in the EU as FCM 784 at SML 5 mg/kg; the same chemistry also works at 0.1-0.5 wt% as a foam-cell nucleator in extruded polystyrene (Aksit and co-workers, 2019). An aliphatic trisamide, CAS 160535-46-6, carries an FDA cap of 0.25 wt% under FCN 860 and an EU SML of 5 mg/kg under FCM 870; its trade name is unconfirmed and not stated here. Structure and dosage for the full class of trisamide clarifiers are covered separately.

7. Polymeric nucleators (polyvinylcyclohexane)#

Polymeric nucleators such as polyvinylcyclohexane (PVCH, CAS 25498-06-0) are hydrogenated polystyrene chains that crystallize before polypropylene does and then nucleate it, and 21 CFR 178.3295 clears them at up to 0.1 wt% of the polyolefin. PVCH is generated directly in the polymerization reactor, in the route Borealis markets as BNT, rather than compounded in afterward, which sets it apart from every other class on this page. Sub-micron PTFE particles and stereocomplex PLA are the other polymeric nucleators used across plastics, though neither is established for PP specifically in our source library. No dosage other than the 21 CFR 178.3295 legal maximum is established for PVCH.

8. Beta nucleating agents#

Beta nucleating agents such as gamma-quinacridone, calcium pimelate, NU-100 and TMB-5 steer polypropylene into its trigonal beta crystal form, which is tougher and less stiff than the standard alpha form. Gamma-quinacridone (E3B) was identified as a beta nucleant by Leugering in 1967; Jozsef Varga (Budapest University of Technology and Economics) reviewed the class in 2002. Calcium pimelate (CAS 19455-79-9) carries an FDA cap of 0.15 wt% under FCN 793 and an EU listing under FCM 820; NU-100 (CAS 153250-52-3) carries an FDA cap of 0.2 wt% under FCN 713 and an EU SML of 5 mg/kg under FCM 772; TMB-5 (CAS 15088-29-6) has no EU 10/2011 entry and no FCN found. The beta form is metastable and converts back to alpha on heating or strain, creating micro-voids, the basis of microporous PP film and battery separators. The full list of beta nucleating agents sits on its own page.

Nucleating Agent vs Clarifying Agent in Polypropylene: What Is the Difference?#

A clarifying agent is a nucleating agent that works at such a high nucleus density that the crystal superstructures end up smaller than the wavelength of visible light, so the part becomes see-through instead of merely stiffer. Every clarifier is a nucleator, but not every nucleator is a clarifier: the difference is nucleus density, not chemistry class. In PP a clarifier is almost always a melt-soluble sorbitol or nonitol acetal or a trisamide, or occasionally a very fine phosphate salt, chosen because it reaches the ultrahigh density that particulate salts such as NA-11 or talc do not.

• Nucleus density: a clarifier reaches a far higher nucleus count per unit volume, shrinking crystalline superstructures below the wavelength of light
• Solubility: clarifiers dissolve in the PP melt and recrystallize on cooling, while most general nucleators stay solid throughout processing
• Optical result: every clarifier also raises nucleus density, so it improves stiffness and cycle time as well as clarity

Grades, haze targets and processing windows for clarified polypropylene are covered on its own page.

Alpha or Beta Nucleation: Which Crystal Form Does the Part Need?#

Alpha nucleation is the default choice for polypropylene because it raises stiffness, heat deflection temperature and clarity, while beta nucleation is chosen only when toughness or a controlled micro-void structure matters more than stiffness. Industrial beta-PP pipe practice, reviewed by Wu and co-workers in Polymers 15 (2023) 3107, combines about 0.02 % alpha nucleator with 0.2 % beta nucleator to keep the beta content stable under fast cooling. TMB-5 at 0.025-0.05 wt%, combined with rotational shear during processing, raised the tensile strength of PP pipe to 40.98 MPa against 33.62 MPa without shear, according to Abudurezhake and co-workers in 2024. Chain defects in random copolymers and single-site PP reduce beta-nucleation efficiency, a finding reported by Wang, Gahleitner and co-workers at Borealis in 2020.

Table (mini). Alpha versus beta nucleation in PP

Which Nucleating Agent Is Best for Each Polypropylene Application?#

The best nucleating agent for polypropylene depends on what the part has to do: a particulate salt for stiffness and cycle time, HPN-20E where warpage decides, a soluble clarifier where the part has to be see-through, and a beta nucleator where toughness matters more than stiffness. Table 3 sets out the recommended class, example grades and regulatory level for every major PP application.

Table 3. Master selection table

FDA and EU limits are legal maxima, not recommended dosages. Where no supplier dosage is published, the table says so. Trials decide the final level.

Request quotes for nucleating agents and clarifiers for PP: grade or CAS, target property, volume, country, through the plastic additive supplier finder. Converters comparing grades before an RFQ can also download the PP Nucleator and Clarifier Selection Chart (PDF), available with email, role and company.

Thin-wall injection moulding and rigid packaging#

Thin-wall packaging is the largest use of nucleators in polypropylene, because the crystallization temperature decides when the part can be ejected and therefore how short the cycle is. Simanke and co-workers found in 2016 that HPN-68L at 1,000-2,200 ppm accelerates crystallization more efficiently than sodium benzoate or DMDBS at the same loading. Milliken states that 4 Hyperform HPN grades deliver UL-validated energy savings of 5-8 % in thin-wall lids, and that Millad NX 8000 cuts cycle time by more than 10 %. Cycle-time additives across polymers are listed under additives for injection moulding, which covers the same nucleation lever alongside mould-temperature and wall-thickness design.

Caps, closures and low-warpage parts#

Caps and closures use Hyperform HPN-20E because its anisotropic particles orient in the flow and balance shrinkage between the flow and cross-flow directions, which is what keeps a closure round. FDA FCN 608 caps HPN-20E at 0.25 wt% in all polyolefins. HDPE closures use the same nucleator family for the same warpage-control reason, since the particle geometry that balances shrinkage in PP works the same way in HDPE. Slip, torque and warpage additives specific to this product form are on additives for caps and closures.

Clarified PP for housewares, bottles and medical parts#

Clarified polypropylene for housewares, thin-wall bottles and medical parts is built on random copolymer PP plus a soluble clarifier, and the processing temperature has to stay above the clarifier's dissolution temperature or the part stays hazy. Random copolymer PP is the dominant resin base for clarified PP. Milliken states that clarified PP is used in more than 22 markets worldwide and that it opens extrusion blow moulding to PP in competition with PVC and PET. ADEKA reports a haze record of 2.2 % at 1 mm for its TRANSPAREX grade, against a market low of 3.2 %, third-party verified and awarded a Guinness World Records title in 2025. Sterilization and biocompatibility rules for this product group are on additives for medical plastics.

Automotive and talc-filled PP#

Automotive polypropylene uses nucleation for downgauging: ADEKA reports that 0.1 wt% of ADK STAB NA-27 lets a part be made 10 % thinner at the same load, which it converts into about 9 kg of material saved per 90 kg of PP per vehicle. Talc-filled PP, typically grades from T10 to T40, is the dominant automotive compound, and talc nucleates as a side effect of its reinforcing role. Because talc also adsorbs antioxidants, talc-filled automotive grades need a correspondingly stronger stabilizer package. The complete interior and exterior package is on additives for automotive plastics, and talc and calcium carbonate loadings for this segment are on fillers for polypropylene.

PP sheet and thermoforming#

Thermoformed polypropylene sheet is nucleated to control sag during heating and to shorten the cycle on the forming line, and Milliken introduced Hyperform HPN 58ei for sheet and thermoforming at K 2025. Nucleated PP homopolymer entered thermoformed packaging specifically for the haze and stiffness gain nucleation provides, a shift the trade press was already noting by 2013. No dosage is published for HPN 58ei, so this page names the grade and its purpose only, without a loading figure.

PP pipe and beta-nucleated PP-R#

Beta-nucleated polypropylene is the pipe grade: PP-R for hot water and pressure pipe uses a beta nucleator because the trigonal beta form resists slow crack growth better than the stiffer alpha form. Industrial practice combines about 0.02 % alpha nucleator with 0.2 % beta nucleator to control the beta content through fast cooling. TMB-5 at 0.025-0.05 wt%, applied with rotational shear, raised pipe tensile strength to 40.98 MPa against 33.62 MPa unsheared, per Abudurezhake and co-workers in 2024. Ageing of beta-nucleated PP-R in chlorinated hot water has been studied by Fischer and co-workers at Johannes Kepler University Linz in 2019. Pressure-pipe formulations in full are on additives for plastic pipes.

Recycled PP (PCR and regrind)#

Recycled polypropylene is nucleated to recover the stiffness and cycle time that contamination and thermal history cost it, and the Association of Plastic Recyclers rates nucleating agents among the Design Preferred workhorse additives for rigid PP. ADEKA sells CYCLOAID UPR-011, an antioxidant-plus-nucleator package built specifically for recycled polyolefins. Milliken states that clarifiers are used in PCR-PP and that Millad ClearX 9000 reduces the need to segregate rPP streams by feedstock, though its exact chemistry is undisclosed. Millad NX 8000 ECO carries RecyClass certification and APR recognition. Regrind and PCR dosing specifics are covered under nucleating agents for recycled plastics, and the full restabilization package is on additives for recycled plastics.

How Much Nucleating Agent Does Polypropylene Need?#

Polypropylene needs between 150 ppm and about 1 wt% of an organic nucleator or clarifier, and 0.5-5 wt% of talc, with the exact level set by the nucleator class, the target property, the melt temperature and the food-contact cap. Five factors drive that decision.

• Nucleator class and efficiency, since a trisamide works at 150-200 ppm while a particulate salt needs 1,000-2,200 ppm for the same effect
• Whether clarity or stiffness is the target, because a clarifier has to reach ultrahigh nucleus density while a general nucleator only has to raise Tc
• Process temperature, since a soluble clarifier has to dissolve, at about 220 °C for traditional sorbitols and lower for Millad NX 8000, or the part stays hazy
• Food-contact cap, a hard ceiling regardless of the technical optimum
• Recyclate content, since PCR contamination and thermal history often call for a stronger package than virgin resin needs

More is not always better: DMDBS optics worsen above 1 wt%, and demixing starts above 2 wt%, so overdosing a clarifier can undo the clarity it is meant to achieve. Nucleators and clarifiers at ppm level are almost always let down from a masterbatch, since accurate neat metering is impractical on a line. Worked example: a 10 wt% clarifier masterbatch let down at 2 % gives 0.2 wt%, or 2,000 ppm, in the part (0.10 × 2 % = 0.2 %); check other ratios in the let-down ratio calculator. FDA and EU limits are legal maxima, not dosages.

How Do Nucleating Agents Interact with Other Additives in Polypropylene?#

A nucleating agent never works alone in polypropylene: calcium stearate can deactivate a sodium nucleator, pigments nucleate on their own and distort shrinkage, and talc pulls antioxidant out of the melt. Table 4 sets out each interaction and what a formulator does about it.

Table 4. Nucleator interactions with other PP additives

Simanke and co-workers documented the calcium stearate antagonism with sodium benzoate directly in their 2016 study. Kisuma's quintinite grade, surface-treated with cis-1,2-cyclohexanedicarboxylic acid, combines acid scavenging with nucleation under FDA FCN 2476, cleared at up to 2,000 ppm in polyolefins. Phthalocyanine pigments raise flow-direction shrinkage across a 1-5 wt% transparent-masterbatch range, which is why Milliken markets its ClearTint polymeric colorants specifically as non-nucleating for use in clarified PP. The choice between calcium stearate and hydrotalcite as the base acid scavengers for polyolefins is made on that page, and shrinkage data by pigment class sits on pigment-induced warpage.

How Is Nucleation Measured in Polypropylene?#

Nucleation in polypropylene is measured first by differential scanning calorimetry, where the crystallization peak on cooling moves to a higher temperature, and then confirmed on the part by haze, flexural modulus, heat deflection temperature and shrinkage. Sample preparation and cooling rates for this method are set out in full on DSC testing.

Table 5. Nucleation test methods

DSC: crystallization temperature and nucleation efficiency#

Differential scanning calorimetry is the standard nucleation test for polypropylene: the sample is cooled at a fixed rate, typically 10 °C/min, and the peak of the crystallization exotherm gives the crystallization temperature Tc. Tc is compared against an unnucleated reference resin from the same base, since no absolute pass or fail Tc value for nucleated PP is established in our source library. The Fillon nucleation-efficiency scale, NE = (Tc,NA − Tc,1) / (Tc,2max − Tc,1) × 100 %, is the standard way to express how close a given nucleator comes to the maximum achievable Tc, and commercial iPP nucleators reach at best 60-70 % on that scale. Crystallization half-time from isothermal DSC is the key metric for PLA and PET rather than for PP, where the cooling-scan Tc is the metric that matters.

Haze and clarity: ASTM D1003 and ISO 14782#

Haze is the percentage of transmitted light scattered by more than 2.5 degrees, measured to ASTM D1003-21 or ISO 14782, and it is the number that decides whether a clarifier has done its job. ASTM D1003 procedure A uses a hazemeter and procedure B a spectrophotometer, and the standard is not equivalent to ISO 13468-1 or ISO 14782, so results from different standards should not be compared directly. Material above 30 % haze counts as diffusing rather than clear, and moves to ASTM E2387 instead. Clarity, the narrow-angle scattering below 2.5 degrees, governs see-through sharpness separately from haze. Procedure A and procedure B differ, as haze and clarity measurement explains in full.

Stiffness, HDT and shrinkage checks#

The property checks that confirm nucleation on a real part are heat deflection temperature to ASTM D648 or ISO 75, flexural or tensile modulus, notched impact strength and the shrinkage difference between the flow and cross-flow directions. HDT is run at 0.455 MPa or 1.82 MPa, 2 °C/min, to a 0.25 mm deflection, and nucleating agents raise PP HDT at either load. Impact is measured to ISO 180 or ASTM D256 for Izod and ISO 179 for Charpy, and tensile properties to ISO 527 or ASTM D638; stiffness rises while impact strength falls as nucleation proceeds. The toughness that nucleation costs is measured as impact strength (Izod, Charpy), covered in full on its own testing page.

Which Nucleating Agents Are Allowed in Food-Contact Polypropylene?#

Food-contact polypropylene may contain only nucleating agents that are listed in Regulation (EU) No 10/2011 within their specific migration limit, or cleared in the US under 21 CFR 178.3295 or a Food Contact Notification held by the supplier. Neither system uses the word "approved": this page writes "listed", "authorised" or "cleared under 21 CFR 178.3295", or names the FCN that covers a given grade. Regulation (EU) No 10/2011 also sets a generic overall migration limit of 10 mg/dm2, or 60 mg/kg for infant food, alongside every substance-specific SML shown below, and every FDA Food Contact Notification is effective only for its notifier and that notifier's customers, so the supplier, not the chemistry alone, decides compliance.

EU: Regulation (EU) No 10/2011 entries and SMLs#

Regulation (EU) No 10/2011, consolidated on 16 March 2025, lists the common polypropylene nucleators in Annex I, most of them with a specific migration limit of 5 mg/kg. Table 6 sets out the food-contact matrix for every nucleator and clarifier covered on this page, EU entry against US clearance.

Table 6. Food-contact matrix for PP nucleators

FDA caps are maximum use levels, not recommended dosages. An FCN is effective only for the notifier and its customers, so the same chemistry from another supplier may not be covered.

Annex II metal limits ride on several entries: aluminium at 1 mg/kg, lithium at 0.6 mg/kg and zinc at 5 mg/kg since Regulation (EU) 2020/1245, never the 25 mg/kg figure some older sources state. The sodium in sodium benzoate falls under the separate Annex I salt rule instead of carrying its own metal SML. SML, OML and the salt rule are explained on specific migration limits, and EU 10/2011 sets out the mechanics behind the table above.

US: 21 CFR 178.3295 and company-specific FCNs#

In the United States, 21 CFR 178.3295 lists 8 clarifying agents for polymers with fixed use limits, and everything newer runs through a Food Contact Notification that is effective only for its notifier and that notifier's customers. Recent nucleator FCNs illustrate how fast this list keeps changing.

• Milliken's trisamide (CAS 2649373-38-4), FCN 2440, 31 July 2025, up to 0.08 wt%, permitted in baby bottles
• Kisuma's quintinite nucleator and acid scavenger, FCN 2476, 12 February 2026, up to 2,000 ppm in polyolefins
• Two HPN-20E-type calcium salts from Sinoview and Jiyi, FCN 2483 and FCN 2495, both March 2026
• ADEKA's disodium N-benzoyl-L-aspartate, FCN 2357, 2024, up to 0.3 wt% in PP
• ADEKA's biphenol/triazine clarifier, FCN 2344, 15 June 2024, up to 0.15 wt% in PP
• Calcium tert-butylphosphonate, FCN 2211, up to 0.15 wt%, including infant formula contact

Since about 2021, new FCNs routinely exclude infant formula and human milk contact; FCN 2211 and FCN 2440 are the exceptions above. FCN 2344 (possibly TRANSPAREX) and FCN 2440 (possibly Millad ClearX 9000) are unconfirmed, so this page cites only the FCN number and notified chemistry, never the trade name. Why FDA Food Contact Notifications bind only the notifier, and the clearance structure generally, are set out in FDA food contact rules.

The talc classification watch#

Talc is the one nucleator in polypropylene with a pending EU classification: the Committee for Risk Assessment adopted an opinion on 20 September 2024 recommending Carc. 1B, but talc is still not in CLP Annex VI as of the 1 July 2026 consolidation, so no harmonised classification applies yet. IARC classified asbestos-free talc as Group 2A, probably carcinogenic to humans, in 2024 (Stayner and co-workers, The Lancet Oncology, 2024). Proposition 65 lists only talc containing asbestiform fibres, since 1 April 1990, not talc generally. Milliken markets its nucleating grades on a talc-free basis, citing this pending classification. This page uses "proposed" and "recommended", never "classified" or "banned", since the entry has not reached CLP Annex VI.

Who Supplies Nucleating Agents for Polypropylene?#

Nucleating agents for polypropylene come from a small group of specialty chemical producers, and the same chemistry often appears under several brand names as more suppliers file their own Food Contact Notifications for it. Table 7 lists the main producers, brand lines and notable grades.

Table 7. Producers, brand lines and notable grades

Buyers should compare grades by CAS number and by the Food Contact Notification that actually covers the supplier they intend to buy from, not by trade name, since the same base chemistry can carry different FCN coverage depending on who notified it. No market-size figure for the nucleating and clarifying agent family is established in our source library, so this page lists producers without a market value. Plants, grades and FCN holdings by company are in the directory of nucleating and clarifying agent suppliers.

Request quotes for nucleating agents and clarifiers for PP: grade or CAS, target property, volume, country, through the plastic additive supplier finder.

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What Else Goes into a Nucleated Polypropylene Formulation?#

A nucleated polypropylene compound still needs the whole stabilizer package: the nucleator changes how the part solidifies, but nothing about how it survives processing, heat or sunlight. The full package covers a phenolic antioxidant plus a phosphite for the melt, a thioester for long-term heat ageing, an acid scavenger, HALS and a UV absorber outdoors, the nucleating or clarifying agent covered on this page, antistats, slip and antiblock for BOPP film, fillers, impact modifiers and, where required, flame retardants. The full PP package is on additives for polypropylene, covering every additive class this page references alongside nucleation.

The rest of the PP additive package#

Every PP compound carries a phenolic antioxidant with a phosphite before any nucleator is added, and outdoor parts add a hindered amine light stabilizer on top. Impact modifiers, typically olefin elastomers, restore the toughness that nucleation costs when a formulation needs both stiffness and impact resistance at once. Dosage by grade for the base antioxidant package is on antioxidants for polypropylene, and toughness lost to nucleation is restored with impact modifiers for polypropylene.

Nucleating agents for polyethylene, PET, PLA and nylon#

Polyethylene, PET, PLA and nylon are nucleated for different reasons than polypropylene: PE for warpage, clarity and cycle time, PET and PLA because they crystallize far too slowly on their own, and nylon mainly for cycle time. HDPE and LLDPE crystallize fast, so nucleation there targets clarity, cycle time, warpage and stiffness (Seven, Cogen and Gilchrist, 2016); HPN-20E, HPN-68L and a calcium norbornane salt carry separate FCNs for HDPE, LLDPE and LDPE. PET nucleates chemically: sodium from sodium benzoate reacts with PET chain ends, forming anionic end groups that also cut molecular weight (Wang and co-workers, 2024). PLA needs a nucleator plus a hot mould at 80-110 °C or annealing; Nagarajan, Mohanty and Misra (Guelph, 2016) showed LAK-301 at 1 wt% cuts the half-time at 140 °C from 61 to 1.8 minutes. Details are on nucleating agents for PLA and nucleating agents for polyethylene.

Is talc a nucleating agent?#

Yes: talc nucleates the alpha form of polypropylene at 0.5-5 wt%, and it keeps nucleating when it is used at 10-40 wt% as a reinforcing filler, which is why talc-filled PP is already partly nucleated before any dedicated nucleator is added. That side effect is one reason talc-filled automotive PP rarely carries a separate nucleator on top of the filler package.

Does a nucleating agent make polypropylene stronger?#

A nucleating agent makes polypropylene stiffer, not tougher: flexural modulus and heat deflection temperature rise, while impact strength falls, a trade-off that beta nucleation reverses. No numeric modulus value for nucleated PP is established in our source library, so the answer here stays directional rather than quoting a before-and-after figure. Beta nucleators such as calcium pimelate and NU-100 push the balance the other way, raising toughness at the cost of some of the stiffness gain alpha nucleation provides.

Why does clarified polypropylene smell or turn hazy?#

Clarified polypropylene turns hazy when the melt never reaches the clarifier's dissolution temperature, which is about 220 °C for traditional sorbitol clarifiers and about 210 °C for 0.4 wt% MDBS. Above 1 wt% DMDBS, optics also worsen even at the correct processing temperature, so overdosing is a second route to the same hazy result. An aldehyde odour is sometimes reported in sorbitol-clarified PP; this page notes it as a reported issue only, without a confirmed chemical mechanism.

Are nucleating agents toxic?#

No nucleating or clarifying agent used in polypropylene is on the REACH Candidate List, Annex XIV, Annex XVII or Proposition 65, and the common grades carry no harmonised hazard classification at all. HPN-68L, HPN-20E, DMDBS, Millad NX 8000 and Irgaclear XT 386 are not classified in their notifications. NA-11 self-classifies H332 and H411 in a minority of notifications, and the NA-21 main component carries a harmonised Aquatic Chronic 2, H411 classification (CLP Annex VI index 013-010-00-5), the one exception. Several grades, including HPN-68L, HPN-20E and NU-100, simply have no active REACH dossier found under their current identifier, a gap in the record rather than proof of non-registration.

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