Additives for Polypropylene (PP): The Complete Formulation Guide to 24 Additive Families

Polypropylene carries a tertiary carbon on every repeat unit, oxidises there and breaks its own chains, so no commercial polypropylene grade is sold without additives: this guide lists all 24 additive families used in PP, with dosage, function and the package each application needs. Even a plain moulding grade leaves the reactor with under 400 ppm of phenolic antioxidant in it, so what does a finished compound actually contain? A finished polypropylene compound carries between two and eight of the 24 families, at levels spanning 50 ppm for a laser marking additive and 30 wt% of the compound for an intumescent flame retardant system.

The 24 families sort into 7 functional groups, named here in the order they keep everywhere on this site: property modifiers, fillers and reinforcements, flame retardants and other functional additives, stabilizers, colorants and masterbatch, processing modifiers, and surface and optical modifiers. Only the stabilizer group appears in every polypropylene grade. The other 6 groups are selected by application, which is why a clarified drinking cup and a talc-filled dashboard carrier share nothing below the antioxidant.

Isotactic commercial polypropylene melts at 160-166 °C, crystallises to 30-60 % and has a density of 0.895-0.93 g/cm3, and every additive decision below follows from those three numbers. This guide covers the beta-scission mechanism, the 24 families with their PP dosage in wt% and ppm, the master table, 8 application packages from housewares to recycled PP, dosing and compounding, the processing window, the interactions that break packages, the test methods, the food-contact and recyclate rules, and the suppliers. Every grade named here has a record in our plastic additives database.

Table T1. The standard polypropylene package at a glance.

Levels are typical formulation ranges from our source library, not legal limits. Food-contact limits are in Table T5.

Why Does Polypropylene Need Additives?#

Polypropylene needs additives because of one structural detail: the methyl group on every repeat unit leaves a tertiary carbon that oxidises faster than any bond in polyethylene, and the radical formed there splits the chain instead of joining it. Isotactic polypropylene melts at 160-166 °C and is processed 40 to 80 °C above that melting point, in air, in a machine that shears it. Neat PP also has a limiting oxygen index of about 18 vol% O2, measured at 17.5-17.8 by ASTM D2863-23e1 and ISO 4589-2, which puts it among the most readily ignited commodity plastics, and it is embrittled below 0 °C.

Five jobs cover everything additives do in a polypropylene compound, and they are the same five jobs plastic additives do in every polymer. The five jobs are listed below in the order a compounder meets them.

1. Protection against thermo-oxidative, photo-oxidative and catalytic degradation, by antioxidants, acid scavengers, UV stabilizers and metal deactivators.
2. Modification of a property the polymer already has, by impact modifiers, nucleating agents, fillers, reinforcing fibres and coupling agents.
3. Addition of a property polypropylene lacks entirely, by flame retardants, antimicrobials and laser marking additives.
4. Control of the melt in the machine, by peroxides for controlled rheology, lubricants and polymer processing aids.
5. Control of the part surface, by slip agents, antiblock additives, antistatic agents, antifog additives and anti-scratch additives.

Polypropylene is unusual in how little of that package is optional, and every polymer has its own guide under additives by polymer.

How does polypropylene degrade? Beta-scission at the tertiary carbon#

Thermo-oxidative degradation of polypropylene runs in three steps: oxygen abstracts the hydrogen on the tertiary carbon, the radical becomes a hydroperoxide, and the hydroperoxide decomposes into fragments that cut the chain by beta-scission. The tertiary carbon is the carbon that carries the methyl group, and its carbon-hydrogen bond is the weakest in the repeat unit, so abstraction happens there rather than anywhere else on the backbone. The resulting alkyl radical adds oxygen, forms a hydroperoxide, and that hydroperoxide splits into an alkoxy radical and a hydroxyl radical, each of which starts a new oxidation cycle. Beta-scission then breaks the backbone one bond away from the radical site, which is why oxidation of polypropylene shortens chains instead of joining them.

Polyethylene fails the other way round. In PE the radicals recombine, so degraded polyethylene crosslinks and forms gels, while degraded polypropylene chain-scissions and thins. The practical consequence is a measurement: because melt flow rate is read at 230 °C under a 2.16 kg load for polypropylene, chain scission shows up directly as a rising MFR, and a compound whose MFR climbs from pass to pass is a compound whose stabilizer reserve is running out; see additives for polyethylene for the gel-forming counterpart.

What happens to an unstabilized polypropylene compound?#

An unstabilized polypropylene compound does not survive its own processing: every pass through the extruder cuts chains, the melt flow rate climbs, and the part that comes out is weaker and yellower than the one before it. Commodity PP grades therefore leave the reactor already carrying less than 400 ppm of phenolic antioxidant as base stabilization, enough to get the pellet to the compounder and not enough to get a part through its service life. In the closed-loop recycling study by Knoben and colleagues (2025), the oxidation induction temperature of polypropylene at reprocessing cycle 5 was 198 °C without added antioxidant against 257 °C with it, a temperature rather than a time value. The family page for antioxidants for polypropylene carries the dose data by grade.

Four failures show up in the part itself, and they appear in this order as the stabilizer reserve is consumed.

• Melt flow rate rise, seen first as flash, short shots or a filling pattern that changes between batches.
• Yellowing, from conjugated carbonyl and quinoid structures formed during oxidation.
• Embrittlement, as the average molecular weight falls and the impact strength with it.
• Surface chalking outdoors, where photo-oxidation erodes the surface layer and releases pigment and filler particles.

Which polypropylene grade are you formulating? PP-H, PP-R and PP-B#

Three polypropylene grades take three different additive packages: homopolymer (PP-H), random copolymer (PP-R) and block or impact copolymer (PP-B, also called ICP). PP-H is propylene only, the stiffest and the most crystalline of the three, and it is the base of housewares, closures, BOPP film and fibres. PP-R carries a small amount of ethylene distributed randomly along the chain, which lowers crystallinity and melting point and improves transparency, and it is the grade used for plumbing and hydronic heating pipe. PP-B carries a separate ethylene-propylene rubber phase made in the reactor, which is why it survives impact at low temperature and why it dominates automotive and crate applications.

The package changes with the grade in three places. PP-B rarely needs a separate impact modifier, because the elastomer phase is already there, while PP-H in a cold-service part does. PP-R needs a long-term thermal package built around a thioester rather than a processing package, because pipe is judged over decades. Homopolymer PP also needs more antifog additive than the random copolymer at equal film thickness, so a grade swap changes the antifog dose as well as the seal temperature.

The 24 Additive Families Used in Polypropylene#

Polypropylene uses 24 additive families, grouped by the same 7 functions used across this reference: property modifiers, fillers and reinforcements, flame retardants and other functional additives, stabilizers, colorants and masterbatch, processing modifiers, and surface and optical modifiers. The families PP does not use are as telling: polypropylene needs no plasticizer, no PVC heat stabilizer, no hydrolysis stabilizer and no chain extender, because it has no chlorine to lose, no ester bond to hydrolyse and no polycondensation equilibrium to restore. Of the 7 groups, only the stabilizers appear in every grade; the other 6 are chosen by application.

1. Property modifiers (6 families)#

In polypropylene, property modifiers change what the polymer does rather than how long it lasts; PP uses 6 of them: impact modifiers, nucleating agents, clarifying agents, compatibilizers, coupling agents and peroxides for controlled rheology. Four of the six act on the crystalline structure or the rubber phase, and two act on an interface.

Impact modifiers#

Impact modifiers are elastomer phases, mostly polyolefin elastomers, EPR and EPDM, that disperse as micron-scale rubber particles in polypropylene and stop a crack before it runs.

An ENGAGE-type polyolefin elastomer at 2-5 %, typically 3 %, in a 70/30 HDPE/PP recyclate raises impact strength and elongation roughly threefold, and POLYBOND 3150 and 3002 at 5 % in recycled PP and nylon raise notched Izod by about the same factor. Impact copolymer grades carry an in-reactor EPR phase instead, while compounds add EPDM or SEBS. Polypropylene is embrittled below 0 °C, which is why the family exists.

Nucleating agents#

Nucleating agents give the polypropylene melt more crystal nuclei, so it solidifies at a higher temperature, in smaller spherulites, with a shorter cycle and a stiffer part. Crystallization temperature measured by DSC is the property that moves.

ADK STAB NA-27 at 0.1 wt% allowed a 10 % thinner part, which Adeka reports as about 9 kg of lightweighting per 90 kg of polypropylene per vehicle, and Milliken's Hyperform HPN grades carry a UL-certified 5-8 % energy saving in thin-wall lids. The best commercial polypropylene nucleators reach 60-70 % on the Fillon self-nucleation efficiency scale. The FDA caps NA-11 at 0.30 wt% in PP and at 0.10 wt% for conditions of use A to H, and caps HPN-20E and HPN-68L at 0.25 wt%; EU Regulation 10/2011 sets a specific migration limit of 5 mg/kg for NA-11 (FCM 749), the HPN-20E acid (FCM 816) and HPN-68L (FCM 817).

Clarifying agents#

Clarifying agents are nucleators that dissolve in the polypropylene melt and recrystallise as nanofibrils, so the crystals stay smaller than the wavelength of visible light and the part looks clear instead of milky.

DMDBS (Millad 3988) works at 0.2-1 wt%, older ultra-clear generations needed 3,000-4,000 ppm, and the trisamide Irgaclear XT 386 works at 150-200 ppm. Sorbitol clarifiers dissolve in polypropylene only to a few thousand ppm and need about 220 °C to go into solution, with MDBS at 0.4 wt% dissolving at about 210 °C. Milliken credits Millad NX 8000 with about 15 % energy saving and more than 10 % cycle-time reduction. The FDA caps DMDBS at 0.4 wt%, Millad NX 8000 at 0.5 wt% under FCN 825 and Irgaclear XT 386 at 250 ppm under FCN 824.

Compatibilizers#

Compatibilizers hold a polypropylene blend together where two polymers will not mix, which in practice means recycled polypropylene contaminated with polyethylene. They sit at the interface and stop the dispersed domains from coalescing.

Polyethylene contamination in recycled PP-B cuts slow-crack-growth resistance by up to 70 %, and 5 % polypropylene in recycled HDPE cuts it by up to 40 %. A polyolefin elastomer at 2-5 % in a 70/30 HDPE/PP blend is the worked example, and maleated polyolefins serve where a polar phase is present.

Coupling agents#

Coupling agents bond an inorganic surface to the polypropylene matrix, because neither talc nor glass nor wood flour sticks to a non-polar polyolefin on its own. One end reacts with the mineral, the other entangles with the polymer.

Maleic anhydride grafted polypropylene is the standard answer in PP, optimal at 1 wt% for flexural properties, where it gives a 24.7 % gain, and at 3 wt% for tensile strength, modulus and impact. Glass fibre arrives carrying 0.5-2.0 wt% silane sizing, and amino-silane sized glass needs a maleated polypropylene to complete the bridge. Grafting competes with beta-scission during reactive extrusion, and the scission intensifies with peroxide content.

Peroxides for controlled rheology (visbreaking)#

Peroxides are the one additive family that degrades polypropylene deliberately: a controlled dose cuts the longest chains, narrows the molecular-weight distribution and raises the melt flow rate to the value a fibre line needs. The mechanism is the same beta-scission that stabilizers prevent, run on purpose and stopped at a target MFR.

Controlled-rheology polypropylene feeds fibre spinning and melt-blown webs, where a narrow distribution gives even filament diameter. Perkadox PM-60ST-GR is reported to lower melt flow index and raise the melt strength of recycled polypropylene by long-chain branching, a patented route. In crosslinked PP/POE foam, electron-beam treatment with up to 8 phr of TMPTMA, that is 8 parts per hundred parts of resin, reaches at most 55 % crosslinking at 15 kGy, while polypropylene melt viscosity falls above 2 kGy.

2. Fillers and reinforcements (2 families)#

Fillers and reinforcements replace polymer volume or carry load in polypropylene, and they are the families that change the package around them, because mineral surfaces adsorb stabilizer. PP uses 2 of them: fillers and reinforcing fibres.

Fillers (talc, calcium carbonate, barium sulfate)#

Fillers in polypropylene are mineral powders, mainly talc and calcium carbonate, that raise stiffness and heat resistance and lower cost, at 10-40 wt% of the compound. Calcium carbonate is used at 20-40 % as the cheaper route to stiffness, and barium sulfate reaches up to 70 % in PP and PS where density is the point.

Talc is also studied as a nucleating agent at 0.5-5 wt%, the range Kandemir (2022) worked in, and plastics took 32 % of US talc sales in 2024 according to the USGS Mineral Commodity Summaries 2025. Talc adsorbs phenolic antioxidant onto its surface, so a filled compound needs a stronger stabilizer package than the unfilled grade it came from. It is listed in EU Regulation 10/2011 as FCM 615 with no specific migration limit. Its hazard classification is moving: the ECHA Risk Assessment Committee opinion of 20 September 2024 recommends Carc. 1B and STOT RE 1, but talc is not in CLP Annex VI as of the 1 July 2026 consolidation, so the classification is proposed and not in force, while IARC placed asbestos-free talc in Group 2A in 2024.

Reinforcing fibres#

Reinforcing fibres, almost always chopped glass in polypropylene, carry mechanical load that the polymer cannot, but only if a coupling agent bonds the fibre surface to the matrix. Without that bond the fibre acts as a stress concentrator.

Glass fibre for polypropylene carries 0.5-2.0 wt% silane sizing, and an amino-silane sizing needs a maleated polypropylene to couple to the matrix. Our source library holds no verified glass loading range for polypropylene, so this page gives none; the loadings and sizing chemistries sit on the glass-filled polypropylene page.

3. Flame retardants and other functional additives (3 families)#

Functional additives give polypropylene a property it does not have at all; PP uses 3 of them: flame retardants, antimicrobials and laser marking additives. Their dosages span the widest range on this page, from 50 ppm for a laser marker to 30 wt% for an intumescent flame retardant.

Flame retardants#

Flame retardants are the largest additive dose polypropylene ever carries: an intumescent ammonium polyphosphate system needs 22-30 wt% of the compound to reach UL 94 V-0. The intumescent route builds a swollen carbon char that shields the polymer below it, which is why the loading is so high.

A formulated intumescent APP product such as Clariant's Exolit AP 750 or AP 766 needs 22-30 wt% for V-0, while a PAPP to MPP system at 2:1 reaches V-0 at 21 wt% total, including in recycled polypropylene. Adding 0.25 wt% zinc oxide or manganese oxide to an APP and pentaerythritol system gives a limiting oxygen index of 30 % with V-0, and 1.5 wt% zinc oxide raises LOI to 43.7 %. On the mineral route, coated magnesium hydroxide at 185.7 phr gives LOI 30.2 in a halogen-free cable compound according to Huber, and 10 wt% zinc borate with 10 wt% MDH in a PP and calcium carbonate compound gives LOI 29.4. In the cone calorimeter at 35 kW/m2 under ISO 5660-1, peak heat release falls from 1,148-1,332 kW/m2 for neat PP to 220-255 kW/m2 for an intumescent PP.

Antimicrobials#

Antimicrobial additives stop bacteria and fungi growing on a polypropylene surface, and in PP they are dosed in parts per million, not per cent. Silver is the dominant active, carried on a zeolite so that release is slow.

Silver nanoparticles on zeolite are effective in polypropylene at 80-160 ppm silver, reported at close to 100 % antibacterial efficiency. Silver zinc zeolite is approved under the EU Biocidal Products Regulation for product types 2, 7 and 9 from 1 March 2026 to 29 February 2036, and an antimicrobial polypropylene article is a treated article under that regulation.

Laser marking additives#

Laser marking additives turn polypropylene, which barely absorbs a laser beam, into a plastic that takes a permanent code without ink. The additive absorbs at the laser wavelength and converts the energy locally into a colour change.

Loadings sit in the parts-per-million range. Graphene at 50 ppm produces dark laser marks in polypropylene, and lanthanide-doped oxide markers changed no tensile, impact or flexural property in PP and ABS at loadings up to 250 ppm.

4. Stabilizers (4 families)#

Stabilizers are the only group present in every polypropylene grade; PP uses 4 of them: antioxidants, acid scavengers, UV stabilizers and metal deactivators. Each intercepts the oxidation cycle at a different point, so they are dosed as systems.

Antioxidants#

Antioxidants are the one family no polypropylene grade leaves without: a hindered phenol interrupts the radical chain by donating a hydrogen to the peroxy radical, and a phosphite reduces the hydroperoxides to alcohols before they split the chain.

Commodity polypropylene grades carry less than 400 ppm of phenolic antioxidant as base stabilization, and the compounder adds to that. Irganox 1010 is used in polyolefins at 0.05-0.4 wt% and Irgafos 168 at 0.05-0.2 wt%, at a phosphite to phenol ratio of 1:1 to 4:1. For long-term heat at 150 °C the phenol to thioester ratio shifts to about 20:80, while about 80:20 suits processing stabilization. Phenolics also cause gas fading, and the phenol-free remedy is a hydroxylamine with a phosphite, such as Irgastab FS 042, listed in EU Regulation 10/2011 as FCM 768 with use limited to 0.1 % in polyolefins and excluded for fatty foods. The FDA figures are legal maxima, not recommended dosages: under 21 CFR 178.2010, Irganox 1010 is limited to 0.5 % of all polymers, Irganox 3114 and ADK STAB PEP-36 to 0.25 % in PP, and Naugard 445 to 0.3 % in PP for non-fatty foods only.

Acid scavengers#

Acid scavengers neutralise the chloride and other acidic residues that Ziegler-Natta and metallocene catalysts leave in polypropylene, which would otherwise corrode tooling and consume the phenolic antioxidant.

Calcium stearate is used in polyolefins at up to 1,000 ppm as acid scavenger and neutraliser, and hydrotalcite of the DHT-4A type and zinc oxide are the alternatives where calcium stearate causes plate-out or colour. Kisuma's Setogem RD is used at 200-300 ppm in polypropylene as both a nucleator and an acid scavenger. Because calcium and zinc stearate also lubricate, this is the first point where two families in the package overlap in one substance.

UV stabilizers (HALS and UV absorbers)#

UV stabilizers protect polypropylene outdoors, where photo-oxidation attacks the same tertiary carbon that thermal oxidation does, only faster. A hindered amine light stabilizer regenerates through the nitroxyl cycle and scavenges radicals throughout the part, while a UV absorber intercepts the photons.

Dosage is set by part thickness and application. HALS run at 0.2-0.8 wt% in PP and HDPE tape, 0.05-0.5 wt% for a UV-3853-type HALS in PP and TPO, and 0.1-1.4 wt% in PP fibres, with Tinuvin 791 at 0.1-0.8 wt% in thick sections and tapes and Tinuvin 111 at 0.1-1.0 wt% in fibres. The benzoate synergist UV-2908 runs at 0.1-0.5 wt% alongside HALS in thick-section PP. Carbon black absorbs the ultraviolet radiation that would otherwise degrade the polymer, which is why black tape needs less organic light stabilizer. One combination has to be watched: thioester antioxidants antagonise HALS.

Metal deactivators#

Metal deactivators bind copper and other transition-metal ions that would catalyse oxidation of polypropylene where the polymer touches metal. The chelating group wraps the ion so that it can no longer decompose hydroperoxides into radicals.

Plumbing defines the family in PP: PP-R and PP-B pipe in contact with copper fittings carries a metal deactivator alongside the long-term thermal package. Irganox MD 1024 is listed in EU Regulation 10/2011 as FCM 675 with a specific migration limit of 15 mg/kg.

5. Colorants and masterbatch (2 families)#

Colorants give polypropylene its colour, and masterbatch is the form in which nearly every additive above actually reaches the machine. Both change the compound in ways unrelated to their nominal function.

Colorants and pigments#

Colorants in polypropylene are not a cosmetic decision: pigment particles act as heterogeneous nuclei, so changing colour shifts the crystallization temperature exactly as a nucleating agent does, and with it shrinkage, warpage and cycle time.

A transparent phthalocyanine green masterbatch at 1-5 wt% raised shrinkage in the flow direction by 13.6-22.3 % against neat polypropylene, and an opaque chromium and copper oxide masterbatch raised it by 49.5-58.3 %, which is where warpage in coloured parts comes from. Carbon black is capped at 2.5 % w/w in EU food-contact plastics as FCM 411. Titanium dioxide has no harmonised EU classification, the General Court having annulled it on 23 November 2022, a judgment upheld on 1 August 2025.

Masterbatch#

Masterbatch is how polypropylene additives are actually dosed: a concentrate in a polyolefin carrier, let down at a fixed ratio on the machine. The carrier resin matters as much as the active content, because an incompatible carrier shows up as gels or streaks.

The BOPP masterbatch types in use are antiblock, antistat, antifog, migrating slip, non-migrating slip and white, so a converter switches performance by switching masterbatch rather than resin. The let-down ratio, not the concentrate content, is what the processor controls. Ampacet REC-NIR-BLACK is a near-infrared-detectable black masterbatch certified for PP and HDPE rigid packaging, which keeps a black part visible to a sorting line.

6. Processing modifiers (2 families)#

Polypropylene needs far less processing help than PVC, so this group is small in PP: lubricants and metal stearates, and polymer processing aids. PVC needs a balanced internal and external lubricant system that polypropylene never does; see additives for PVC for that contrast.

Lubricants and metal stearates#

Lubricants in polypropylene are mostly the metal stearates already present for acid scavenging, doing a second job at the metal interface, where they lower the force needed to release the part.

Calcium and zinc stearate therefore do triple duty in PP as acid scavenger, lubricant and release agent, and zinc stearate is described as the most powerful mould-release agent among the metal soaps. The food-contact limit is a metal limit rather than a substance limit: the EU specific migration limit for zinc is 5 mg/kg under Annex II of Regulation 10/2011, which also constrains the zinc stearate fraction of Hyperform HPN-20E.

Polymer processing aids#

Polymer processing aids remove melt fracture from polypropylene film and tape lines, and they are the one PP additive family under direct regulatory pressure. The additive coats the die land, so the polymer slips rather than sticking and tearing.

Fluoropolymers are the established chemistry, and the FDA limits VDF-HFP fluoropolymer processing aid to 0.2 % in olefin polymers. PFAS-free acrylic and polyethylene-glycol alternatives are in commercial use. The EU universal PFAS restriction is pending rather than adopted: the ECHA Risk Assessment Committee issued its final opinion on 2 March 2026 and the Socio-Economic Analysis Committee opinion is still a draft.

7. Surface and optical modifiers (5 families)#

Surface and optical modifiers work at the boundary of the polypropylene part, not inside it; PP uses 5 of them: slip agents, antiblock additives, antistatic agents, antifog additives and anti-scratch additives. Four of the five work by migrating to the surface, which is why their effect develops over days and decays over months.

Slip agents#

Slip agents are fatty acid amides that bloom out of polypropylene to the film surface and cut its coefficient of friction, at 500-1,200 ppm. The amide is only partly soluble in the polymer, so it migrates outward and forms an ordered layer.

Erucamide and oleamide are dosed at 0.05-0.12 wt%, the same 500-1,200 ppm, and erucamide is preferred in polypropylene for its higher heat resistance. On a PP fibre it forms a surface bilayer about 4 nm thick. Erucamide and silica antiblock together lower the coefficient of friction more than either alone, because the amide adsorbs onto the antiblock particle. Erucamide in PP is measured by ASTM D6042, using liquid chromatography with ultraviolet detection, at a detection limit of about 2 ppm.

Antiblock additives#

Antiblock additives are mineral or polymer particles that stand proud of the polypropylene film surface so two layers cannot weld together in the roll. Blocking is an area-of-contact problem, and the particle reduces that area.

Talc antiblock in polypropylene blown film is used at up to 5 wt%. Diatomaceous earth and talc are trialled at 2,500-10,000 ppm and calcium carbonate at 2,500-20,000 ppm, because calcium carbonate needs 250-300 % more for the same effect. Tospearl silicone resin beads come in 1.8-2.3, 2.3-3.1, 4.0-5.0 and 8.5-10.5 µm grades, and the working rule in BOPP is a bead diameter of about 40 % of the skin-layer thickness.

Antistatic agents#

Antistatic agents drain the charge polypropylene builds up, because untreated PP sits at 1e15 to 1e16 ohm surface resistivity. A migrating antistat reaches the surface and attracts a thin water film that conducts the charge away; a permanent antistat builds a conductive phase through the part.

Glycerol monostearate and ethoxylated amines together hold more than half the antistatic market, and a migrating antistat such as GMS gives an effect for about 1 to 2 months. An antistatic plastic sits at 1e9 to 1e13 ohm. Permanent systems hold longer: a PA6-PEG-QAS antistat at 20 wt% in polypropylene measured 3.64e11 ohm on day 0 and 4.69e10 ohm on day 60. In US food packaging, antistatic and antifogging agents are covered by 21 CFR 178.3130.

Antifog additives#

Antifog additives spread condensed water into a continuous layer on polypropylene packaging instead of letting it stand as droplets, and PP needs two to three times the level polyethylene needs. The additive lowers the surface tension between water and polymer.

Antifog in polypropylene film is dosed at 0.5-2.0 % against 0.2-0.6 % in polyethylene film across the Palsgaard grade range, and homopolymer PP needs more than the random copolymer at equal thickness. The chemistry is non-ionic surfactants, mainly polyglycerol esters and sorbitan esters, chosen by whether the pack stays clear hot or chilled.

Anti-scratch additives#

Anti-scratch additives lower the friction between a hard tip and a talc-filled polypropylene surface, so the mark it leaves stays below the visible threshold. Scratch visibility in filled PP is a whitening effect caused by the filler debonding under the tip.

Fatty amides and silicone masterbatches are the two routes used on talc-filled interior parts, where scratch shows first. Anti-scratch silicone conflicts with paintability, so a part that will be coated takes the amide route. Scratch is measured by the OEM methods PV 3952 and GMW 14688, both crosshatch tests.

Complete List of Polypropylene Additives: All 24 Families in One Table#

The complete list below gives all 24 polypropylene additive families with their group, their job in PP, the typical level, example substances and the page that holds the selection detail. Row order matches the group and family order used everywhere else on this page, and no value in the table is new: each repeats a figure stated above. Where our source library holds no verified polypropylene-specific level, the cell says so rather than estimating.

Table T2. The 24 additive families used in polypropylene.

Every grade named above has a record in the plastic additives database, with CAS number, function, dosage range and regulatory status.

Additive Packages for Polypropylene by Application#

Two polypropylene compounds made from the same reactor grade can share only their antioxidant: a clarified drinking cup and a talc-filled dashboard carrier take opposite packages from the second additive onwards. The package follows the application, not the polymer. Eight applications cover the commercial bulk of polypropylene, and Table T3 gives, for each one, the families that are mandatory, the families that are typically optional, and the one number that defines the compound. You can filter the 24 families by application and function with the additive finder by polymer and function, and the general framework is on how to select plastic additives.

Table T3. Additive packages for polypropylene by application.

Injection-moulded housewares, crates and caps#

A moulded polypropylene houseware or closure needs only three things in its base package: a phenolic antioxidant with a phosphite, an acid scavenger and, on nearly every modern cap line, a nucleator that buys back cycle time. The antioxidant and phosphite handle the melt at 200 to 240 °C and whatever regrind returns to the hopper; the acid scavenger at up to 1,000 ppm keeps catalyst residues off the tool steel. The nucleator is where the money is: Milliken's Hyperform HPN grades carry a UL-certified 5-8 % energy saving in thin-wall lids, and ADK STAB NA-27 at 0.1 wt% allowed a 10 % thinner part, saving material on every shot and seconds on every cycle.

What the moulder actually changes, once the base package is fixed, is colour, and colour causes most of the trouble. Pigments nucleate polypropylene, so a colour change alters shrinkage: a transparent phthalocyanine green masterbatch at 1-5 wt% raised shrinkage in the flow direction by 13.6-22.3 %, and an opaque chromium and copper oxide masterbatch by 49.5-58.3 %. A tool cut for natural PP delivers out-of-tolerance parts in a deep colour unless the shrinkage is requalified, and the machine-side detail is on additives for injection molding.

Clarified polypropylene for transparent packaging#

Clarified polypropylene only works if the clarifier dissolves: a sorbitol clarifier needs a melt around 220 °C, and a part moulded colder stays hazy however much was added. MDBS at 0.4 wt% dissolves at about 210 °C, which sets the lower bound of the processing window for the whole compound. The solubility ceiling matters too, because sorbitol clarifiers dissolve in polypropylene only to a few thousand ppm, so overdosing buys no clarity and can produce plate-out and taste problems instead.

Dosage then depends on the clarifier generation. DMDBS such as Millad 3988 works at 0.2-1 wt%, earlier ultra-clear generations needed 3,000-4,000 ppm, and the trisamide Irgaclear XT 386 reaches the same effect at 150-200 ppm. Milliken credits Millad NX 8000 with about 15 % energy saving and more than 10 % cycle-time reduction, and reports clarified PP in use across more than 22 markets. Food contact turns the ceiling from technical into legal: the FDA caps DMDBS at 0.4 wt%, Millad NX 8000 at 0.5 wt% under FCN 825 and Irgaclear XT 386 at 250 ppm under FCN 824, while EU Regulation 10/2011 sets migration limits of 5 mg/kg for NA-11, HPN-20E and HPN-68L. Grade-level selection sits on the clarified polypropylene page.

Talc-filled polypropylene for automotive interiors and under-hood parts#

Talc-filled polypropylene is the workhorse of car interiors, and the talc changes the rest of the package: mineral surfaces adsorb phenolic antioxidant, so a filled compound needs more stabilizer than the unfilled grade it came from. Talc runs at 10-40 wt%, the T10 to T40 range, and raises modulus and heat deflection temperature in proportion. A coupling agent completes the interface, and a metal deactivator appears wherever the part touches a copper conductor. Songwon sells SONGXTEND 2124 for high heat stabilization in polypropylene automotive applications.

Automotive packages are then constrained by tests that have nothing to do with mechanics. Interior compounds are screened by VDA 278 for emissions at 90 °C for 30 minutes, by VDA 270 for odour at 80 °C for 2 hours on a 1 to 6 scale, by DIN 75201 for fogging, where BHT raises the result, and by FMVSS 302, which limits burn rate to 102 mm/min. Anti-scratch additives are added because a talc-filled surface whitens under a hard tip, and pigment choice is constrained again by nucleation and warpage. Lightweighting runs through the nucleator: ADK STAB NA-27 at 0.1 wt% gives a 10 % thinner part, about 9 kg of polypropylene saved per 90 kg per vehicle according to Adeka. OEM specifications are on additives for automotive plastics.

BOPP and cast polypropylene film#

Polypropylene film is where the surface additives earn their place: a BOPP web that will not open, feed or seal is a converting problem, not a polymer problem. Biaxially oriented polypropylene is produced by the tenter route or the double-bubble route, and in both the additive functions are delivered as masterbatch: antiblock, antistat, antifog, migrating slip, non-migrating slip and white.

Slip runs at 500-1,200 ppm, and erucamide is preferred over oleamide for its higher heat resistance. Antiblock is dosed by particle size rather than by mass alone: talc reaches up to 5 wt% in blown polypropylene film, while Tospearl silicone beads are supplied in 1.8-2.3, 2.3-3.1, 4.0-5.0 and 8.5-10.5 µm grades, with the working rule that bead diameter is about 40 % of the skin-layer thickness. Erucamide and silica antiblock reinforce each other, since the amide adsorbs onto the particle. Antifog, where the film wraps produce or chilled food, runs at 0.5-2.0 % in polypropylene. The market context is the mono-material shift, with biaxially oriented polyethylene grades such as Ampacet BIAX4CE competing for the same structures, and the film view across polymers is on additives for packaging film.

Polypropylene fibres, tapes and nonwovens#

Polypropylene fibre stabilization has one extra enemy: gas fading, the yellowing that appears when nitrogen oxides from a gas-fired oven or from storage convert a phenolic antioxidant into a coloured quinone methide. The remedy is to remove the phenol rather than to add more of it, using a hydroxylamine with a phosphite. Irgastab FS 042 is the reference product, listed in EU Regulation 10/2011 as FCM 768, with use limited to 0.1 % in polyolefins and excluded for fatty foods.

Light stabilization is the second fibre-specific decision, because a fibre has an extreme surface-to-volume ratio and almost no reservoir. HALS in polypropylene fibres run at 0.1-1.4 wt%, with Tinuvin 111 at 0.1-1.0 wt%, against 0.2-0.8 wt% in the thicker PP and HDPE tape used for woven sacks and ropes. Rheology is the third: controlled-rheology polypropylene made by peroxide visbreaking gives the narrow molecular-weight distribution that melt-blown webs and fine denier spinning need. Polypropylene nonwovens are reported to go largely into diapers and sanitary products, a share our source marks as needing a citation. Spinning-line detail is on additives for synthetic fibres.

PP-R and PP-B pipe#

Pipe tests a polypropylene stabilizer package for decades rather than minutes, so the package shifts from processing protection to long-term thermal stability. The working combination is a high-molecular-weight hindered phenol with a thioester at a ratio of about 20:80 for 150 °C service, the inverse of the roughly 80:20 phenol-rich ratio used for processing stabilization. A metal deactivator joins the package wherever the pipe meets copper fittings, because copper ions catalyse hydroperoxide decomposition at exactly the point where the joint is least accessible.

PP-R is the random copolymer grade used for potable plumbing and hydronic heating, and PP-B serves where impact at low temperature matters more than clarity. Recyclate is not allowed in pressurised gas or drinking-water polypropylene pipe systems at all. For non-pressure multilayer pipes the door is open but specified, and EN 13476-3 Annex D lists the items that have to be agreed for PP recyclate: oxidation induction time, ash content, foreign polymers, impurities, pigments and additives, volatiles, tensile properties and origin. Pipe standards are on additives for plastic pipes.

Flame-retardant polypropylene compounds#

A flame-retardant polypropylene compound is mostly flame retardant: reaching UL 94 V-0 with an intumescent ammonium polyphosphate system takes 22-30 wt% of the compound, which changes stiffness, flow and cost at the same time. The starting point is a polymer with a limiting oxygen index of about 18 vol% O2, which is why so much additive is needed to move it.

Three routes are in commercial use and they differ in loading more than in result. The intumescent APP route runs at 22-30 wt% with formulated products such as Exolit AP 750 and AP 766, while a PAPP to MPP system at 2:1 reaches V-0 at 21 wt% total, in recycled polypropylene as well. Metal oxide synergists cut the loading further: 0.25 wt% zinc oxide or manganese oxide in an APP and pentaerythritol system gives LOI 30 % with V-0, and 1.5 wt% zinc oxide gives LOI 43.7 %. The halogen-free mineral route runs through magnesium hydroxide (MDH) at cable loadings, with coated MDH at 185.7 phr giving LOI 30.2, and 10 wt% zinc borate with 10 wt% MDH giving LOI 29.4. Cone calorimetry under ISO 5660-1 at 35 kW/m2 confirms the result, peak heat release falling from 1,148-1,332 kW/m2 to 220-255 kW/m2. Grade selection is on flame retardants for polypropylene.

Recycled polypropylene (r-PP)#

Recycled polypropylene arrives with its stabilizer partly spent, so the first additive decision is restabilization: a phenol and phosphite blend at 0.1-0.3 wt% is the level tested across multipass extrusion at 250 °C, using products such as Songwon SONGNOX 11B and 21B. The measurable gain is service life: XP 2121 at 0.15-0.4 wt% raised days to embrittlement at 150 °C from about 25 to 37-42, and Recyclobyk 4371 at 0.75 wt% held properties to the twentieth reprocessing cycle. In the closed-loop study by Knoben and colleagues (2025), dosing 500 ppm of primary and 1,000 ppm of secondary antioxidant per cycle let Irgafos 168 build from about 650 ppm at cycle 1 to more than 1,200 ppm at cycle 5, and open-loop regranulate still held more than 150 ppm of intact Irgafos 168.

Three further problems are additive problems. Polyethylene contamination cuts slow-crack-growth resistance of recycled PP-B by up to 70 %, which is the compatibilizer case. Odour is treated physically: 4 wt% zeolite cut odour intensity of mixed polyolefin recyclate by 45 %. Sortability is decided by the original formulation, and the Association of Plastic Recyclers rates a rigid PP package by density, preferring below 0.970 g/cm3, requiring testing between 0.970 and 1.0 and calling 1.0 and above non-recyclable, with colour lightness L above 40 and near-infrared reflectance above 10 % preferred. Dose data by resin are on restabilization of recycled plastics, and the cross-polymer view is on additives for recycled plastics.

How Are Polypropylene Additives Dosed, Delivered and Compounded?#

Polypropylene dosage is written in weight percent and parts per million of the compound, not in phr: phr is the PVC and rubber convention, and mixing the two is the most common error in a polyolefin specification. The difference is the basis. A phr figure is parts per hundred parts of resin, so a formulation containing 185.7 phr of magnesium hydroxide contains 65 wt% of it, while a wt% figure is already a share of the finished compound. The conversion rules are on PHR (parts per hundred resin), and a recipe can be converted directly with the PHR to weight percent calculator, which applies the relation wt%_i = phr_i divided by total phr, times 100.

Additives reach polypropylene at three points, and the point decides the form. Base stabilization is added at the reactor and is already in the pellet, which is why a commodity grade arrives with under 400 ppm of phenolic antioxidant. A compounder adds the rest on a twin-screw line, as powder, liquid or one-pack blend. A converter adds the last increment at the machine as masterbatch, at a let-down ratio checked with the let-down ratio calculator.

The compounding step changes the additive as well as distributing it. Dispersive mixing breaks agglomerates of talc, antiblock or pigment and distributive mixing spreads them, and a badly dispersed nucleator acts as a defect rather than a nucleus. Residence time and shear also consume stabilizer, so the dose that leaves the extruder is lower than the dose that entered it, the phosphite in particular converting to phosphate as it works. Twin-screw settings and side-feeding of fillers are covered on plastic compounding.

What Is the Processing Window of Polypropylene?#

The processing window of polypropylene is set from below by the clarifier and from above by beta-scission: a clarified grade needs a melt around 220 °C to dissolve its sorbitol, while every extra degree and every extra pass raises the melt flow rate. Isotactic polypropylene melts at 160-166 °C, so the window is wide in principle and narrow in practice, because the additives rather than the polymer define both edges. Chain scission is read from the melt flow rate (MFR / MFI / MVR), measured for polypropylene at 230 °C under 2.16 kg.

Three limits close the window, and they are listed below in the order a process engineer meets them.

1. Melt temperature, bounded below by the clarifier dissolution point, about 210 °C for MDBS at 0.4 wt% and about 220 °C for the traditional sorbitols, and above by thermo-oxidative degradation.
2. Shear and residence time, which cut chains mechanically and thermally, so the same compound gives a different MFR on a long screw than on a short one.
3. Regrind fraction, because every pass consumes stabilizer reserve, and that reserve separates a compound that tolerates 30 % regrind from one that does not.

Which Additives Fight Each Other in Polypropylene?#

Polypropylene packages fail more often from interaction than from underdosing: the thioester that protects a pipe compound at 150 °C weakens the HALS in the same formulation. The five synergies that matter in polypropylene are listed below.

• Hindered phenol with phosphite, at a phosphite to phenol ratio of 1:1 to 4:1, the standard processing system.
• Hindered phenol with thioester, at about 20:80 for long-term heat at 150 °C.
• HALS with a UV absorber, and with the benzoate synergist UV-2908 at 0.1-0.5 wt% in thick sections.
• Erucamide with silica antiblock, where the amide adsorbs onto the particle and the pair lowers the coefficient of friction more than either alone.
• Zinc oxide or manganese oxide at 0.25 wt% with an intumescent ammonium polyphosphate system, which lifts LOI to 30 % and delivers V-0.

Five antagonisms recur in polypropylene formulations, and they are listed below in the order of how often they appear in failure analysis.

• Thioesters antagonise HALS, so a compound needing both heat and weathering protection takes a different heat stabilizer.
• Talc adsorbs phenolic antioxidant, so a filled compound needs a stronger package than its unfilled base grade.
• Phthalocyanine pigments nucleate polypropylene and change shrinkage, which appears as warpage in coloured parts.
• Anti-scratch silicone conflicts with paintability, so a coated interior part cannot use the silicone route.
• Amine and amide antistats react with acidic additives and with halogenated flame retardants, destroying both functions.

The full cross-family matrix is on additive interactions.

How Are Polypropylene Additive Effects Tested?#

Four measurements carry most polypropylene additive work: melt flow rate for chain scission, oxidative induction time for the stabilizer reserve, crystallization temperature by DSC for nucleation, and haze for clarity. Each maps to one family and each has a current standard edition, which matters because oxidative induction time by ASTM D3895-19 and by ISO 11357-6 are both run at 190-220 °C but are not technically equivalent, so a result has to name its method. Oven ageing is the slow counterpart, run for polypropylene under ASTM D3012 with a specimen rotator, which produced the r-PP result of about 25 days to embrittlement at 150 °C unstabilised against 37-42 days with 0.2-0.4 % XP 2121. All methods are indexed under testing plastic additives.

Table T4. Test methods for polypropylene additive effects.

Which Rules Apply to Additives in Polypropylene?#

No rule restricts polypropylene itself; the rules apply to the additives in it, and they apply differently depending on whether the part touches food, a child, drinking water or a recycling stream. Three regimes cover the field. Food contact is governed in the EU by Regulation (EU) No 10/2011, consolidated 16 March 2025, and in the US by 21 CFR Parts 177 and 178. Chemical restriction runs through REACH Annex XVII and the authorisation list, the POPs Regulation, California Proposition 65 and the US Toxic Substances Control Act. End-of-life rules, which are newer, reach the formulation through recyclability design guides and through the ban on oxo-degradable products. Every instrument is summarised in plastic additive regulations.

Food contact: FDA 21 CFR and EU 10/2011#

The two food-contact systems ask different questions of a polypropylene compound: the FDA sets a percentage cap per additive and a specification for the resin itself, while the EU sets a migration limit the finished article has to meet. The US route starts with the resin: 21 CFR 177.1520 item 1.1a defines food-contact polypropylene by density 0.880-0.913 g/cm3, melting point 160-180 °C, a maximum n-hexane extractable fraction of 6.4 % after 2 hours at reflux, and maximum xylene solubles of 9.8 % at 25 °C, with the reflux extraction method applying to polypropylene and not to polyethylene. An additive is then permitted by a listing in 21 CFR 178 or by a Food Contact Notification, at a stated percentage ceiling. Those percentages are legal maxima, never recommended dosages: each additive is listed under a numbered section rather than granted an approval. The 21 CFR sections are mapped on FDA food contact rules.

The EU route starts with the substance and ends with the article. An additive has to appear on the Union list of Regulation (EU) No 10/2011 with an FCM number, and it then carries either no specific migration limit, a numeric SML in mg/kg of food, or a group restriction shared with related substances. Compliance is demonstrated on the finished article by migration testing, so the same additive at the same dose can pass in a thick-walled crate and fail in a thin film. Migration limits and testing conditions are explained on EU 10/2011.

Table T5. Food-contact status of the main polypropylene additives.

Restricted substances and recyclate rules#

Few restrictions name polypropylene, but three reach into its formulation: cadmium pigments are capped at 0.01 % by weight in polypropylene under REACH Annex XVII entry 23, and the pending EU restriction on PFAS would reach the fluoropolymer processing aids used in film. The PFAS restriction is not in force, because the ECHA Risk Assessment Committee issued its final opinion on 2 March 2026 while the Socio-Economic Analysis Committee opinion remains a draft, so a fluoropolymer processing aid at the FDA limit of 0.2 % in olefin polymers is legal today. Talc sits in a similar state: the RAC opinion of 20 September 2024 recommends Carc. 1B and STOT RE 1, but talc is not in CLP Annex VI as of the 1 July 2026 consolidation, so it is proposed and not classified. Entry 23 and the other entries are explained on REACH Annex XVII restrictions.

Recyclate rules work the other way round, restricting what a formulation may contain if the part is to re-enter a stream. Oxo-degradable plastic products have been banned in the EU since 3 July 2021 under Article 5 of Directive (EU) 2019/904, and the Association of Plastic Recyclers rates a degradable additive as making a polypropylene package non-recyclable outright. Density decides the rest for rigid PP: the APR guidance prefers below 0.970 g/cm3, requires testing between 0.970 and 1.0 and treats 1.0 and above as non-recyclable, a mineral-filler limit expressed as a density. The design rules are on design for recycling.

Who Supplies Polypropylene Additives?#

No single company supplies a complete polypropylene additive package: stabilizers come from BASF, Songwon, SI Group, Clariant and Adeka, clarifiers and nucleators are dominated by Milliken and Adeka, and flame retardants and masterbatch come from a third set of suppliers again. A compounder therefore buys from four to six sources for one formulation, and the one-pack blends that stabilizer makers sell exist precisely to reduce that count. Company profiles are in the directory of plastic additive manufacturers and suppliers.

The market these suppliers serve is reported as a range rather than a figure, because analyst scopes differ. MarketsandMarkets put plastic additives at USD 43.5 billion in 2023, IMARC at USD 58.1 billion in 2025 and Precedence Research at USD 63.71 billion in 2025, with Precedence naming polypropylene the largest polymer segment. Songwon describes itself as the world's second-largest polymer stabilizer maker, a company claim rather than an audited ranking. Suppliers ranked by additive sales are on largest plastic additive companies.

Table T6. Suppliers of polypropylene additives and what they supply.

Is Polypropylene Safe? What Its Additives Mean for Health and Recycling#

Questions about whether polypropylene is safe are in practice questions about what was added to it, because the polymer chain itself is an inert hydrocarbon and every substance that can migrate out of a polypropylene part was either put there on purpose or arrived as a by-product. The four questions below each have a measured answer in the literature, though the measurements differ greatly in how settled they are. What follows summarises the evidence on additive detection, PFAS, particle release and recyclability.

Which additives have been found in polypropylene food packaging?#

Analytical surveys of polypropylene food packaging keep finding the same class of substance: not the additive itself, but its degradation product. 2,4-di-tert-butylphenol, known as 2,4-DTBP, is a breakdown product of phosphite antioxidants such as Irgafos 168, measured in BOPP and LDPE food-contact products at up to 45.568 plus or minus 31.513 mg/kg. It is not on the Union list of Regulation (EU) No 10/2011, which makes it a non-intentionally added substance, a NIAS, assessed by the manufacturer rather than authorised by entry.

The detection work itself is a live research area rather than a settled one. Akoueson and colleagues at ANSES and the University of Lille published an analysis of additives in polypropylene and polylactic acid food packaging in Science of the Total Environment in 2022, and that study is currently the second organic result on the query this page targets, which says something about how little formulation-side information exists next to it. The wider study set is reviewed on chemicals migrating from plastic food packaging.

Does polypropylene contain PFAS?#

Polypropylene contains no fluorine by nature, so a PFAS finding in a polypropylene film normally points to one additive family: the fluoropolymer processing aid used to suppress melt fracture. The FDA limits VDF-HFP fluoropolymer processing aid to 0.2 % in olefin polymers, which is the upper bound of the intended content, and PFAS-free acrylic and polyethylene-glycol alternatives are commercially available for lines that choose to remove it.

The regulatory position is pending rather than settled. The ECHA Risk Assessment Committee issued its final opinion on the universal PFAS restriction on 2 March 2026 and the Socio-Economic Analysis Committee opinion is still a draft, so no EU restriction currently applies. The whole PFAS picture is on PFAS in plastics.

Can polypropylene release microplastics?#

Polypropylene containers do shed particles under heat, and the measured amounts come from a small number of studies rather than from a settled body of evidence. Hussain and colleagues (2023) estimated the highest daily intake at 22.1 ng/kg of body weight per day for toddlers consuming microwaved dairy from polypropylene containers and 20.3 ng/kg per day for infants given microwaved water, and reported up to 4.22 million particles released per cm2 during 3 minutes of microwave heating.

Those figures are single-study estimates and are reported here as such, with the authors and year named, rather than as established exposure values. The heating studies are on is it safe to microwave plastic.

How do additives affect polypropylene recycling?#

The additives in a polypropylene part decide whether it can be recycled at all: a density above 1.0 g/cm3 from heavy mineral filling takes a rigid PP package out of the sink-float stream, and a degradable additive takes it out entirely. The Association of Plastic Recyclers prefers a density below 0.970 g/cm3, requires testing between 0.970 and 1.0, and rates degradable additives as making the package non-recyclable, while oxo-degradable plastic products have been banned in the EU since 3 July 2021 under Article 5 of Directive (EU) 2019/904.

Two additive problems follow the material into the recyclate: stabilizer reserve is partly spent, which restabilization at 0.1-0.3 wt% restores, and odour accumulates, which 4 wt% of zeolite reduced by 45 % in mixed polyolefin recyclate. What comes back with the recyclate is on legacy additives in recycled plastic.