Additives for PET Resin: Bottle, Fibre and Film Grades and 21 Additive Families

Polyethylene terephthalate (PET) is a polyester, so it does not simply oxidise like a polyolefin: it hydrolyses, loses molecular weight and loses the intrinsic viscosity every grade is sold on, which is why all 21 additive families used in PET resin exist to hold that number or rebuild it. A water-bottle resin is sold at 0.70 to 0.78 dL/g and a tyre-cord resin at 0.72 to 0.98 dL/g, so what exactly is in the pellet that keeps it there?

PET resin additives fall into six of the seven functional groups used across this reference: property modifiers, fillers and reinforcements, flame retardants and other functional additives, stabilizers, colorants and masterbatch, and processing modifiers. Only the stabilizers and the dryer appear in every PET grade, and the seventh group, surface and optical modifiers, carries no PET-specific level in our data.

This guide follows a PET compound from the ester bond to the purchase order: hydrolysis and acetaldehyde, the viscosity ladder that names every grade, the 21 families and their levels in weight percent and parts per million, the packages for seven grades from water bottle to recycled flake, dosing, the processing window, the interactions, the tests, the rules and the suppliers. About 31 million tonnes of PET were made in 2025 and more than 60 % of it is spun into fibre rather than blown into bottles.

The ten rows below are the package of a standard bottle resin, in the order the ingredients enter it.

Levels are typical formulation ranges from our knowledge base, not legal limits. The FDA percentages are legal maxima, and the food-contact limits are collected in the matrix further down the page.

Why Does PET Resin Need Additives?#

PET resin needs additives because of one bond: the ester linkage that builds the polyester is the same bond that water, heat and ultraviolet light can cut, and every cut lowers the molecular weight the grade was sold on. Condensation polymers such as PET and polycarbonate are more susceptible to hydrolysis and to ultraviolet attack than addition polymers, the glass transition temperature sits at 67 to 81 °C, and the polymer absorbs ultraviolet light from about 360 nm.

Five jobs follow from that chemistry, each owned by one family, and they are the five jobs plastic additives do in every polymer.

• Molecular-weight protection: a hydrolysis stabilizer caps the acid end groups water creates.
• Molecular-weight rebuild: a chain extender joins two short chains into one.
• Taste and odour: an acetaldehyde scavenger binds the aldehyde a preform carries out of the machine.
• Process economics: a reheat additive and a nucleating agent buy back energy and cycle time.
• Shelf life and appearance: an oxygen scavenger, a toner and an ultraviolet absorber protect the contents and the colour.

Each polymer answers those five jobs differently, and the comparison across every polymer sits under additives by polymer.

How does PET degrade? Hydrolysis of the ester bond#

PET degrades by hydrolysis first: a water molecule reaches an ester bond in the melt, the bond cleaves into an acid end group and an alcohol end group, and the chain that was one molecule is now two shorter ones. Each cleavage lowers the intrinsic viscosity the grade was bought on. Thermal degradation works on the same bond at melt temperature, roughly 240 to 320 °C for PET, and photo-oxidation works from the outside, where the Norrish type I route dominates and the Norrish type II route yields acetaldehyde.

A polyolefin fails along a different path, since polypropylene oxidises at its tertiary carbon and polyethylene crosslinks into gels, which is why polymer degradation in a polyester is read as a viscosity loss. The routes are compared on polymer degradation.

Four failures make that chemistry visible on the shop floor.

• Falling intrinsic viscosity from one pass to the next.
• Preform and bottle-wall failure at the stretch-blow step, where a short chain cannot hold the orientation.
• Yellowing and greying, worst in recycled flake.
• Acetaldehyde in the bottle headspace, which a water brand detects before any instrument does.

Where does the acetaldehyde in a PET bottle come from?#

Water tastes of acetaldehyde from 10 to 20 parts per billion, and an unscavenged PET preform leaves the moulding machine carrying about 7.5 parts per million of it, which is why bottle resin for water is the one PET grade that always contains a scavenger. The aldehyde is already in the preform at the parts-per-million level, and light adds more in service, because the Norrish type II route in PET yields acetaldehyde under ultraviolet light.

A scavenger does not prevent the aldehyde, it binds it, and the measured effect is large. Industrial preforms made with an anthranilamide scavenger held 1.25 ppm against 7.5 ppm in the control, and bottled water from them held 5 ppb after 52 days against 79 ppb; in screening work, 500 ppm gave a 71 % reduction. Transport inside the wall is slow, with a diffusion coefficient of 4.2e-16 cm2/s at 23 °C rising to 4.2e-15 cm2/s at 40 °C. The dosage and the regulatory position of acetaldehyde scavengers for PET bottles have their own page.

Which PET grade are you formulating? The intrinsic viscosity ladder#

Intrinsic viscosity, measured in decilitres per gram, is the number that separates one PET grade from the next: 0.40 to 0.70 dL/g for textile fibre, 0.60 to 0.70 for biaxially oriented film, 0.70 to 0.78 for water and general-purpose bottles, 0.78 to 0.85 for carbonated soft drinks, 0.72 to 0.98 for tyre cord, and 1.00 to 2.00 for engineering and monofilament grades. The six rungs below each force an additive decision.

Intrinsic viscosity bands are typical commercial ranges from our knowledge base, not specification tolerances; the test method is covered on the intrinsic viscosity page.

Climbing the ladder changes the package more than it changes the polymer. Resin makers describe the beverage grades as one family built on reheat additives, toners, colorants and oxygen barriers, with the water grade at low intrinsic viscosity plus acetaldehyde suppression, and the heat-set grade at higher intrinsic viscosity with diethylene glycol suppression and crystallisation aids. The measurement itself, and the two standards it runs under, belong to the intrinsic viscosity of PET and recycled PET.

The 21 Additive Families Used in PET Resin#

PET resin uses 21 additive families, grouped by the same seven functions used across this reference, and draws on six of them: property modifiers, fillers and reinforcements, flame retardants and other functional additives, stabilizers, colorants and masterbatch, and processing modifiers.

The families PET does not use are as telling as the ones it does: no plasticizer, no PVC heat stabilizer, no crosslinking peroxide, no clarifying agent and no acid scavenger for catalyst chloride, because the polyester has no chlorine to lose, no tertiary carbon to oxidise and no Ziegler-Natta residue to neutralise, and because a clear bottle gets its clarity from quenching the preform. The heat stabilizer PET never needs is the defining family of additives for PVC.

The seventh group, surface and optical modifiers, reaches PET film as antiblock, antistatic, antifog and matting additives, but carries no PET-specific level in our knowledge base and so carries no number here. Only the stabilizers are in every PET grade.

1. Property modifiers (5 families)#

In PET, property modifiers change the molecule itself rather than protecting it, and the first of them is the one family PET needs more than any other polymer does: PET uses five, namely chain extenders, nucleating agents, impact modifiers, compatibilizers and coupling agents.

Chain extenders#

Chain extenders are the one additive family PET needs and the polyolefins do not: a multifunctional epoxide reacts with the acid and hydroxyl end groups that hydrolysis created and stitches two short chains back into one long one, at 0.5 to 1.5 wt% in recycled PET, where gel content stays at or below 2 % while 3 wt% of ADR-4400 overshoots into about 32 % gel. Joncryl ADR-4368 carries about nine epoxy groups per molecule at a molecular weight of 6,800 g/mol. Pyromellitic dianhydride is the tetrafunctional alternative at 0.2 to 0.3 wt%, and once hydrolysed it promotes degradation instead of extension.

Nucleating agents#

Nucleating agents decide how fast PET crystallises, which sets the cycle time of a CPET tray and the heat resistance of a hot-fill bottle: TMB-5 studied in PET at 0.6 wt% raised the crystallisation temperature by 16.6 °C and impact strength about tenfold, in the 2026 review by Hao. Talc and TMB-5 nucleate physically, while sodium benzoate nucleates chemically, because the sodium ion reacts with PET chain ends and that reaction causes chain scission, as Wang reported in 2024. Sodium saccharin carries an FDA limit of 0.1 wt% in PET under food-contact notification FCN 1148.

Impact modifiers#

Impact modifiers in PET are reactive ethylene copolymers that graft onto the polyester end groups rather than simply dispersing as rubber, which is why they work in a glass-filled recyclate where a non-reactive elastomer does not. Copolymers of the Lotader AX8900 type raised the notched Izod impact strength of a recycled PET and glass-fibre compound from 5.2 to about 8.1 kJ/m2, a gain of 55 % to ISO 180 at 23 °C. Residual glycidyl methacrylate carries the regulatory load, as FCM 220 with a migration limit of 0.02 mg/kg.

Compatibilizers#

Compatibilizers earn their place in PET only when something else is in the stream: a polyolefin flake fraction that will not mix, the normal condition of mixed post-consumer rigid packaging. Kraton reports that CirKular+ C1000 at 10 % raised notched Izod by 50 % and yield strength by 30 % in a 72/18 polypropylene and PET blend, and that C1010 at 5 % raised them by 70 % and 40 % in a post-consumer HDPE and PET blend.

Coupling agents#

Coupling agents in PET sit on the glass rather than in the resin: an epoxy silane applied to the fibre at 0.5 to 2.0 wt% of the aqueous size bath bonds the fibre surface to the polyester matrix. 3-Glycidyloxypropyltrimethoxysilane is FCM 1068, authorised only as a component of glass-fibre sizing for PET, polycarbonate, PBT and thermoset polyesters.

2. Fillers and reinforcements (2 families)#

Fillers and reinforcements in PET belong to the engineering grades at the top of the viscosity ladder rather than to packaging; PET uses two of them, fillers and reinforcing fibres, and both reach the compound through the compounder.

Fillers#

Fillers do a different job in PET than in a polyolefin: talc is added to a polyester to make it crystallise rather than to make it cheaper, and 2 wt% in a bio-polyester analogue cut the crystallisation half-time at 66 °C from 7.69 to 1.95 minutes. Titanium dioxide is the other mineral with a named PET use, as the light barrier in white dairy packaging, and no verified filler loading range for PET exists in our sources.

Reinforcing fibres#

Reinforcing fibres, almost always chopped E-glass in PET, carry the mechanical load the polyester cannot, and only where a silane size and a reactive coupling route bond the fibre to the matrix. E-glass has a density of 2.58 g/cm3, a tensile strength of 3,445 MPa and a modulus of 76.0 GPa, and is FCM 38 on the EU Union list. No verified glass loading range for PET exists, so the loading is set by the compounder.

3. Flame retardants and other functional additives (5 families)#

Functional additives give PET a property the polyester does not have at all, and in PET this is the largest and most distinctive group on the page; PET uses five of them: oxygen scavengers, barrier additives, IR absorbers and reheat additives, acetaldehyde scavengers and odour-control additives, and flame retardants.

Oxygen scavengers#

Oxygen scavengers are the only PET additive family that is meant to react: an oxidisable phase, usually MXD6 or a polybutadiene-containing copolyester, is oxidised in place by a cobalt salt at 50 to 200 parts per million of cobalt metal, so the oxygen never reaches the beer. The Oxbar example blend is 96 % PET with 4 % MXD6 and 200 ppm of cobalt (US 5,021,515, priority 1987), and the catalyst is claimed at 10 to 300 ppm as cobalt metal (US 6,083,585). The European Union caps the scavenger backbone copolymer at 5 % w/w in PET as FCM 979.

Barrier additives#

Barrier additives slow oxygen down without consuming it, and the number that matters is measured on the bottle rather than on the film: a 3-layer PET bottle with 10 % MXD6 admits 0.0075 against 0.027 cubic centimetres per bottle per day at 0.21 atm for plain PET, according to Mitsubishi Gas Chemical, while a blend gives 0.016 at 5 % and 0.011 at 10 %. MXD6 is listed under 21 CFR 177.1500(a)(10)(ii) as nylon MXD-6, and its monomer is FCM 421 with an SML(T) of 0.05 mg/kg.

IR absorbers and reheat additives#

Reheat additives are dosed in parts per million because that is all a preform can take before it greys: carbon black works in PET at 0.1 to 8.0 ppm, preferably 1.5 to 3.5 ppm, and 2.5 ppm raised the 80-second heat-up temperature from 201 to 215 degrees Fahrenheit while holding Hunter haze below 3.0 (US 4,408,004). The inorganic absorbers carry PET-only authorisations: titanium nitride nanoparticles are FCM 807, authorised only in PET up to 20 mg/kg with no migration of nanoparticles, reduced tungsten oxide is FCM 1064, and iron phosphide is FCM 607.

Acetaldehyde scavengers and odour control#

Acetaldehyde scavengers bind the aldehyde inside the polymer instead of preventing it, and PET is the only polymer the European Union authorises anthranilamide for: FCM 164, restricted to PET for water and beverages, with a specific migration limit of 0.05 mg/kg. Anthranilamide (CAS 88-68-6) is claimed at 200 to 500 ppm for effective scavenging (US 6,274,212), the oligomeric grade assessed by EFSA in 2025 at 650 mg/kg in PET migrated 0.0038 mg/kg into 20 % ethanol, and activated charcoal is FCM 713, authorised only in PET at up to 10 mg/kg of polymer.

Flame retardants#

Flame retardants reach PET by a route the polyolefins cannot use: CEPPA, 3-(hydroxyphenylphosphinyl)propanoic acid, is copolymerised into the chain rather than compounded into it, which is how a polyester fibre carries phosphorus without carrying a filler. Where bromine is used instead, sodium antimonate is the antimony(V) synergist, because it is less catalytically active towards polyester depolymerisation than antimony trioxide. Our sources hold no loading range and no UL 94 rating for a flame-retardant PET compound.

4. Stabilizers (4 families)#

Stabilizers are the only group present in every PET grade, and in a polyester their order of importance is not the polyolefin order; PET uses four of them: hydrolysis stabilizers, antioxidants, UV stabilizers and metal deactivators.

Hydrolysis stabilizers#

Hydrolysis stabilizers cap the acid end groups that water keeps creating, and a carbodiimide is the standard answer in a polyester: about 0.5 to 2.5 parts per 100 parts of finished product, or 1.5 to 3.0 wt% of active delivered through a PET masterbatch. Stabaxol I (CAS 2162-74-5) works as a hydrolysis stabilizer, an acid scavenger and a mild chain extender in one molecule, and the polymeric grades are Stabaxol P, MB PET 3040 at 15 % active in a PET carrier and the Carbodilite line. Lanxess states the service-life gain is usually threefold, and the named PET application in our data is monofilament for paper-machine dryer screens, running at about 100 °C in water.

Antioxidants#

Antioxidants in PET are chosen for hydrolytic stability before radical-trapping power, because a conventional phosphite in a resin that still holds moisture hydrolyses before it reaches the hydroperoxide it was bought to destroy, and the 240 to 320 °C window is what makes the choice sharp. The numbers in this family are legal maxima rather than recommended dosages: the calcium phosphonate Irganox 1425 carries an FDA maximum of 0.3 wt% in PET under 21 CFR 178.2010, Irgastab FS 042 has a use limit of 0.25 % w/w in PET and is barred from fatty foods, and the hydrolysis-resistant spiro phosphite Doverphos S-9228 is capped at 0.15 wt% of all food-contact polymers.

UV stabilizers#

UV stabilizers in PET are almost always absorbers rather than hindered amines, because the polyester itself starts absorbing from about 360 nanometres and the job is to intercept that light before the ester bond does. Cyasorb UV-3638, a benzoxazinone, is used across a 0.1 to 10 wt% range according to Mayzo, at about one third of the benzotriazole dosage. Tinuvin 1577 is used at 0.2 to 1.0 wt% according to Mayzo, or 0.2 to 6 wt% including cap layers according to BASF, and both it and Tinuvin 234 carry an FDA maximum of 0.5 wt% in PET.

Metal deactivators#

Metal deactivators bind the transition-metal ions that would catalyse oxidation of the polyester, and PET always has some, because the catalyst that built the chain is still in it. The catalytic metals in polymers are titanium, aluminium and copper, and Irganox MD 1024 is a hindered phenol hydrazide that works as both a primary antioxidant and a copper deactivator. Our sources hold no PET dosage for this family.

5. Colorants and masterbatch (2 families)#

Colour work in PET is mostly corrective rather than decorative, and masterbatch is the form in which nearly every additive above actually reaches the machine; PET uses two families here: colorants, toners and optical brighteners, and masterbatch.

Colorants, toners and optical brighteners#

Colorants in PET are usually there to remove a colour rather than to add one: a blue or violet toner at parts-per-million level masks the yellow that thermal history and recycled flake put into the resin. Lanxess states that nearly all of its Macrolex solvent dyes are cleared for colouring PET at loadings below 0.20 %, a supplier statement rather than a listing, and Solvent Blue 104 is capped by 21 CFR 178.3297 at 0.0004 % by weight of PET. Titanium dioxide has no harmonised EU classification, after the General Court annulled the entry on 23 November 2022 and the appeals were dismissed on 1 August 2025, and optical brightener OB-1 runs at 50 to 1,000 ppm in polyester fibres.

Masterbatch#

Masterbatch is how PET additives are actually dosed, and in PET it is unusually often a liquid: a reheat additive at 5 parts per million cannot be weighed into a blender, so it arrives as a 10 % dispersion in monoethylene glycol. Additive masterbatch typically holds 40 to 65 wt% of active and is let down at 1 to 5 %, and the PET forms in our data are Joule RHB at 10 % active, Stabaxol MB PET 3040 at 15 % active and Amosorb Oxyloop-1 at up to a 3 % let-down.

6. Processing modifiers (3 families)#

Processing modifiers in PET are dominated by one problem the polyolefins do not have, which is water; PET uses three of them: desiccants, lubricants and mould release agents, and slip agents.

Desiccants#

Desiccants are the additive answer to the question every PET moulder asks first, which is what to do about residual moisture, and they are dosed at 1 to 5 % of the resin, roughly 1 % of masterbatch per 0.15 % of water. Moisture in the melt cuts the chain, so the desiccant protects molecular weight, and the masterbatch should be used within 16 to 24 hours of opening the bag.

Lubricants and mould release agents#

Lubricants in PET are pentaerythritol esters doing an interface job, blooming to the mould wall so that a crystalline part releases without a spray. Pentaerythritol tetrastearate (CAS 115-83-3) is an internal mould release for polycarbonate and a processing aid for PET and PBT, covered by FCM 880 with no SML and limited by 21 CFR 177.1580 to 0.5 wt% in polycarbonate. No PET dosage exists in our sources.

Slip agents#

Slip agents lower the coefficient of friction of a PET film web so that it feeds, opens and seals on the converting line, and the dosage ranges published for this family are polyolefin values. The erucamide and oleamide range of 0.05 to 0.12 wt% belongs to polyolefin film, so the controlled property is named here and the number is not.

Complete List of PET Additives: All 21 Families in One Table#

The complete list below gives all 21 PET additive families with their group, their job in the polyester, the typical level where our data holds one, example substances and the page that carries the selection detail.

Eight of the 21 rows carry no PET level, because no verified PET-specific range exists in our sources, and the cell says so rather than borrowing a polyolefin number. Every grade above has a record in the plastic additives database.

Additive Packages for PET by Grade and Application#

Two PET compounds made from the same monomers share almost nothing below the stabilizer line: a 0.74 dL/g water-bottle resin carries an acetaldehyde scavenger and a reheat additive, while a 0.95 dL/g tyre-cord resin carries neither and carries a carbodiimide instead. The package follows the grade, and the grade is named by its intrinsic viscosity.

The machine-side view belongs to additives for plastic bottles and blow-moulded containers, the framework for choosing between families is on how to select plastic additives, and the families can be filtered by grade with the additive finder by polymer and function.

Water and general-purpose bottle resin#

A water-bottle resin is the one PET grade defined by a taste limit rather than a mechanical one: the water has to stay below the 10 to 20 parts per billion at which acetaldehyde becomes audible to a tasting panel, so the scavenger is not optional. The resin sits at 0.70 to 0.78 dL/g, and anthranilamide is dosed at 200 to 500 ppm under FCM 164, restricted to PET for water and beverages.

What the resin maker changes is small and measurable. Scavenged industrial preforms held 1.25 ppm of acetaldehyde against 7.5 ppm in the control, and the bottled water from them held 5 ppb after 52 days against 79 ppb. A reheat additive and a light toner complete the package. Bottled water is a food rather than a drinking-water installation, so the positive lists for plastic additives in drinking-water contact do not govern the pack, and the cross-polymer view sits on additives for food packaging.

Carbonated soft drink and hot-fill bottles#

A carbonated soft drink resin sits a step up the viscosity ladder, at 0.78 to 0.85 dL/g, because the wall has to resist creep under pressure for the life of the pack rather than only survive filling. The reheat additive earns its place here: ColorMatrix Joule RHB runs at about 5 ppm in that resin, SmartHeat RHC at 0.02 to 0.075 %, carbon black at a preferred 1.5 to 3.5 ppm, and titanium nitride at up to 20 mg/kg under its PET-only EU authorisation.

Hot-fill and heat-set bottles add a crystallisation requirement. Resin makers describe the heat-set grade as a higher intrinsic viscosity with diethylene glycol suppression and crystallisation aids, so a nucleating agent joins the package to hold the neck and base geometry at fill temperature. The detail for reheat additives for PET preforms has its own page.

Beer, juice and wine bottles: the oxygen-barrier package#

A beer, juice or wine bottle is the only PET pack that needs two different oxygen strategies at once: a passive barrier that slows oxygen down and an active scavenger that consumes what still gets through. The passive side is MXD6, where a 3-layer bottle with 10 % admits 0.0075 against 0.027 cc per bottle per day for plain PET, and the European PET Bottle Platform caps PA-MXD6 at 5 wt% in clear and 6 wt% in coloured 3-layer bottles without tie layers.

The active side is a separate calculation, and the two numbers are never added together. A cobalt salt at 50 to 200 ppm of cobalt metal oxidises the MXD6 or the polybutadiene segment in place, and the regulatory position is unfinished: the EFSA CEP panel concluded in 2022 that it was not able to conclude on the safety of a polycyclooctene and cobalt stearate scavenger, and the Union list of active and intelligent substances under Regulation (EC) No 450/2009 was still not adopted when we checked it on 22 September 2026. Recyclability turns on the same choice, since the Association of Plastic Recyclers requires an oxygen scavenger to pass PET-CG-01 after ageing per PET-P-12. One route puts the chemistry in the cap, where Avient credits ColorMatrix Capture with up to 24 months of added shelf life; the closure is covered by additives for caps and closures and the wall chemistry by oxygen scavengers for PET bottles.

BoPET film and sheet#

Biaxially oriented PET film works at the lowest useful viscosity of any PET grade, 0.60 to 0.70 dL/g, and its additive package moves from the bulk of the web to its two surfaces. Slip additives set the coefficient of friction, and our sources hold no PET-specific slip level, because the published 0.05 to 0.12 wt% range belongs to polyolefin film.

Light management is the second surface job. Tinuvin 1577 and Cyasorb UV-3638 are the PET film and fibre absorbers, with FDA maxima of 0.5 wt% in PET under 21 CFR 177.1630, and titanium dioxide gives the light barrier of white dairy sheet. Matting additives carry no PET level in our data, so the function is named and no loading is given. The view across polymers sits on additives for packaging film.

PET fibre, filament and tyre cord#

More than 60 % of all PET is spun rather than blown, and the fibre grades sit at the bottom and the top of the viscosity ladder at once: 0.40 to 0.70 dL/g for textile and 0.72 to 0.98 for tyre cord. Textile grades carry an optical brightener, where OB-1 runs at 50 to 1,000 ppm under FCM 422 with an SML of 0.05 mg/kg, and ultraviolet absorbers protect gas-fade colour and tenacity outdoors.

Durable filament is where hydrolysis stabilization becomes the whole formulation. Monofilament for paper-machine dryer screens runs at about 100 °C in water, the named PET application for a polymeric carbodiimide at 1.5 to 3.0 wt% of active. Flame-retarded polyester fibre takes the reactive route, with CEPPA copolymerised into the chain. Spinning-line detail belongs to additives for synthetic fibres.

Glass-filled and engineering PET compounds#

Engineering PET starts at an intrinsic viscosity of 1.00 dL/g and above, which is where the polyester stops being a packaging material and starts competing with PBT and nylon. The reinforcement is chopped E-glass at a loading the compounder sets, since no verified glass loading range for PET exists in our sources, and the interface is made by an epoxy silane at 0.5 to 2.0 wt% of the size bath, authorised as FCM 1068 only for sizing.

Toughness and cycle time are bought separately: a reactive ethylene copolymer raised notched Izod from 5.2 to about 8.1 kJ/m2 to ISO 180 at 23 °C, and a nucleating agent sets the crystallisation rate that decides mould temperature. PET competes with additives for nylon (polyamide) in exactly these parts, the sister polyester takes a different package under additives for PBT, and the reinforcement itself is covered on glass fiber reinforced plastics.

Recycled PET (rPET) and bottle-to-bottle#

Recycled PET arrives with its molecular weight already spent, so the first additive decision is not protection but reconstruction: a multifunctional epoxide at 0.5 to 1.5 wt% rebuilds intrinsic viscosity while keeping gel content at or below 2 %, and 3 wt% overshoots into about 32 % gel. Pyromellitic dianhydride does the same work at 0.2 to 0.3 wt%, and once hydrolysed it promotes degradation rather than extension, which makes drying the additive as important as drying the flake.

Three more families follow the recyclate. A toner masks the yellow of post-consumer flake, a compatibilizer handles the polyolefin fraction that survives sorting, and the antioxidant package has to be rebuilt rather than topped up, which is the subject of restabilization of recycled plastics. Amosorb Oxyloop-1 holds an EPBP accreditation for coloured bottle-to-bottle use at up to a 3 % let-down, and the cross-polymer view of recyclate formulation is on additives for recycled plastics.

How Are PET Additives Dosed, Delivered and Compounded?#

PET dosage is written in weight percent and in parts per million of the resin, never in phr: a reheat additive at 2.5 ppm and a hydrolysis stabilizer at 2 wt% are four orders of magnitude apart, and the same formulation sheet has to carry both. Parts per hundred resin belongs to PVC and rubber, where the recipe starts at 100 parts of polymer, and the conversion into weight percent divides each ingredient by the total parts and multiplies by 100, as set out on PHR (parts per hundred resin). The one exception here is the carbodiimide range of 0.5 to 2.5 parts per 100 parts of finished polyester.

Delivery form follows the dose. Additive masterbatch holds 40 to 65 wt% of active and is let down at 1 to 5 % of the base polymer, so 25 kg per tonne is 2.5 % or a 39:1 ratio. Liquid concentrates are metered by peristaltic pump, which is how a 10 % reheat dispersion reaches 5 ppm in the preform, and gravimetric feeders make parts-per-million accuracy repeatable.

Where the additive enters the chain decides who owns it. Catalyst residue, acetaldehyde scavenger, reheat additive and toner are in the resin as it leaves polymerisation, while chain extenders, impact modifiers, glass fibre and nucleating agents are compounded in later, as covered on plastic compounding.

What Is the Processing Window of PET?#

The processing window of PET is set from below by moisture and from above by the melt: the resin has to be dry before it reaches 240 to 320 degrees Celsius, because water and heat together cut the ester bond faster than either does alone. The glass transition temperature of 67 to 81 °C marks where the amorphous wall of a bottle starts to move, and every extra thermal pass costs intrinsic viscosity that only a chain extender gets back. Three limits define the window.

1. Drying comes first, because excess moisture reduces molecular weight by chain scission. Our sources hold no drying temperature, dew point or residence time for PET, so none is stated, and where pre-drying is unavailable the additive route is a desiccant masterbatch at 1 to 5 %.
2. Melt temperature comes second. The 240 to 320 °C band is shared with PA66, PBT and polycarbonate, and it is why a hydrolysis-resistant phosphite is specified.
3. Regrind comes third, because each pass lowers the intrinsic viscosity of the pellet.

A melt-stability loss also shows up in the melt flow rate (MFR / MFI / MVR) of a polyester compound, while intrinsic viscosity remains the reference measurement.

Which Additives Fight Each Other in PET?#

PET packages fail more often from interaction than from underdosing, and the clearest case is the one that looks like a free lunch: sodium benzoate nucleates PET by reacting with its chain ends, which means it buys crystallisation rate by spending molecular weight. Four pairings work for the formulator.

• A hindered phenol with a hydrolysis-resistant phosphite, trapping radicals and destroying hydroperoxides.
• An ultraviolet absorber with a light stabilizer.
• A carbodiimide doing double duty, as acid scavenger and mild chain extender.
• A chain extender with a nucleating agent in a CPET compound, restoring melt strength and setting the crystallisation rate.

Eight antagonisms run the other way, each with a named mechanism.

• Sodium benzoate nucleates chemically and causes chain scission in doing so, as Wang reported in 2024.
• Hydrolysed pyromellitic dianhydride promotes degradation instead of chain extension.
• Antimony trioxide catalyses polyester depolymerisation, hence sodium antimonate in flame-retardant PET.
• An ultraviolet absorber and an optical brightener compete for the same photons.
• Talc, kaolin and silica adsorb antioxidant and light stabilizer on their acid sites.
• Low-treated titanium dioxide with a phenolic antioxidant causes pinking through titanium-quinone complexes.
• Flame retardants reduce antioxidant effectiveness.
• Carbodiimides and aziridines suppress crystallinity to below 5 % in polylactic acid, which is polylactic acid data and a caution for any crystallising polyester; the same chain extenders are used in additives for PLA (polylactic acid).

Phosphite hydrolysis is the interaction a polyester line meets first, compared on phosphite and phosphonite antioxidants, and the full matrix of additive interactions sits on its own page.

How Are PET Additive Effects Tested?#

Four measurements carry most PET additive work: intrinsic viscosity for molecular weight, residual acetaldehyde for taste, crystallisation temperature by differential scanning calorimetry for nucleation, and haze and yellowness index for what the reheat additive and the recyclate did to the colour. Intrinsic viscosity runs under ASTM D4603 and ISO 1628-5, and acetaldehyde is measured in the preform or in the headspace, with no method number in our sources. Every method below is indexed under testing plastic additives.

Haze is measured to ASTM D1003-21, procedure A on a hazemeter and procedure B on a spectrophotometer, with haze above 30 % counted as diffusing. Yellowness index is reported to ASTM E313-20, reapproved in 2025, and never to the withdrawn D1925. ASTM D3895-19 and ISO 11357-6 are not technically equivalent.

Which Rules Apply to Additives in PET?#

Most rules on plastic additives ignore the host polymer, which makes PET the exception worth knowing: five entries on the EU Union list are authorised in polyethylene terephthalate and in nothing else, namely FCM 164 anthranilamide, FCM 607 iron phosphide, FCM 713 activated charcoal, FCM 807 titanium nitride and FCM 979 the PET, hydroxylated polybutadiene and pyromellitic dianhydride copolymer. Three regimes then apply in parallel: food contact under Regulation (EU) No 10/2011 and 21 CFR, chemical restriction under REACH Annex XVII, CLP and California Proposition 65, and recycled content under the PPWR, Regulation (EU) 2022/1616 and the APR and EPBP design guides, each summarised in our guide to plastic additive regulations.

Food contact: EU 10/2011 and FDA 21 CFR 177.1630#

The two food-contact systems ask different questions of a PET compound: the FDA sets a percentage cap per additive inside 21 CFR 178.2010 and a resin specification in 177.1630, while the European Union sets a migration limit the finished article has to meet. The generic specific migration limit is 60 mg/kg, the overall migration limit is 10 mg/dm2, and a functional barrier has to hold any non-listed substance below 0.01 mg/kg, in the consolidated text of 14 July 2026. The structure of the Union list is explained on EU 10/2011.

Cobalt is the one metal limit a PET formulator can breach through an additive choice, because the oxygen-scavenger catalyst is a cobalt salt: the Annex II limit is 0.05 mg/kg expressed as cobalt, and the catalyst is dosed at 50 to 200 ppm of cobalt metal in the wall. Antimony is capped at 0.04 mg/kg through the antimony trioxide Annex I entry rather than through Annex II, and on the United States side 177.1315 covers PETG and 178.3297 the colorant caps, as mapped on FDA food contact rules. No additive is approved in the abstract: it is listed for a stated condition of use, at a stated level, in a stated polymer.

Modelling shortens the work before any simulant is poured. The Piringer screening model of Annex V 2.2.3, used under Article 18(3), gives PET the constants A_P'* 6.4 and tau 1,577 K for 70 to 175 °C with a molar mass above 32 g/mol, as published in JRC EUR 27529, and hot-fill contact time follows the Annex V formula, t = 120 / 2^((T-70)/10) minutes between 70 and 100 °C. The screening route is explained on additive migration in plastics.

Recycled content and recyclability: PPWR, EU 2022/1616, APR and EPBP#

PET is the only polymer the EU packaging regulation names by itself: Article 7 of Regulation (EU) 2025/40, published in the Official Journal on 22 January 2025 and applying from 12 August 2026, requires 30 % post-consumer recycled content in contact-sensitive PET and in single-use plastic beverage bottles from 1 January 2030 or three years after the implementing act, whichever is later, rising to 50 % and 65 % in 2040, against 10 % for contact-sensitive packaging other than PET. The full timetable is on the EU Packaging and Packaging Waste Regulation (PPWR) page, and the decontamination rules on recycled plastics regulations. Regulation (EU) 2022/1616, in force since 10 October 2022, makes post-consumer mechanical PET recycling suitable technology 1, with at most 5 % input from non-food applications, and EFSA assumes a baseline misuse contamination of 3 mg per kg of PET while the FDA works to a negligible dietary concentration of 0.5 ppb.

The design guides decide what the additive package is allowed to be. The Association of Plastic Recyclers rates reheat additives "Requires Testing" because they can turn flake dark or yellow, and the European PET Bottle Platform requires an oxygen scavenger in clear PET to be thermally stable for five loops with below 0.1 % non-PET content, which is what design for recycling means in a PET bottle. One restriction travels with the recyclate rather than the design: entry 23 of REACH Annex XVII caps cadmium below 0.01 % by weight of the plastic material in listed polymers including PET and PBT, in force since 10 December 2011 under Regulation (EU) No 494/2011, and the other entries are explained on REACH Annex XVII restrictions.

Who Supplies PET Additives?#

No single company supplies a complete PET additive package: reheat additives, oxygen scavengers and toners come from Avient, hydrolysis stabilizers from Lanxess and Nisshinbo, chain extenders from BASF, and the stabilizer and ultraviolet chemistry from BASF, Songwon, Dover Chemical and Syensqo. The plastic additives market is quoted between USD 43.5 billion (2023, MarketsandMarkets) and USD 63.71 billion (2025, Precedence Research), and profiles are in the directory of plastic additive manufacturers and suppliers.

Company data from our source library, with every performance claim attributed to the company that makes it. No company on this page pays for placement.

Ranked by additive sales rather than by PET speciality, the same companies appear on largest plastic additive companies. One input sits outside the additive market and still moves PET costs: the USGS Mineral Commodity Summaries 2026 put the average antimony price at USD 25 per pound in 2025 against USD 10.24 in 2024, tracked on antimony trioxide price.

Is PET Safe? What Its Catalyst Residue and Additives Mean for Health and Recycling#

The safety question about PET separates into three things: the polyester chain, the additives put into it on purpose, and the antimony catalyst that built it. The chain ranks low in the analytical surveys, the additives carry the migration limits set out above, and the catalyst residue is what consumers ask about most, although it is not an additive. Microplastic release is covered under microplastics and additive leaching.

Does antimony leach out of PET bottles?#

The antimony in a PET bottle is not an additive: antimony trioxide is the catalyst that built the polyester chain, and what is left in the wall is residue rather than something chosen for an effect. The substance (CAS 1309-64-4) is classified Carc. 2 H351 under CLP index 051-005-00-X, was listed under California Proposition 65 for cancer on 1 October 1990, and the EU migration limit for the finished article is 0.04 mg/kg expressed as antimony.

Two measurement studies set the scale. Shotyk and Krachler at the University of Heidelberg reported in Environmental Science and Technology in 2007 that antimony in PET-bottled water rose by an average of 90 % over six months across 48 European brands. Westerhoff and colleagues at Arizona State University measured 0.095 to 0.521 ppb of antimony in US bottled water in Water Research in 2008, against an EPA maximum contaminant level of 6 ppb and a WHO guideline of 20 ppb, and calculated 176, 38, 12, 4.7, 2.3 and 1.3 days to exceed that level at 60, 65, 70, 75, 80 and 85 degrees Celsius. The catalyst itself is profiled on antimony trioxide.

Which additives have been measured in PET food packaging?#

Analytical surveys of plastic food packaging rank PET low rather than high: in the 34-product screen by Zimmermann and colleagues at Goethe University Frankfurt and NTNU in 2019, 74 % of extracts were active in at least one in vitro assay, with PVC and polyurethane the most toxic while PET and HDPE showed none or low activity. A survey of synthetic phenolic antioxidants in Chinese food-contact materials found sums from 44.18 to 69,485.12 µg/kg with a median of 2,615.63 µg/kg, and antioxidant 2246 was found mainly in polyethylene and PET.

Non-intentionally added substances are the open edge of the system. 2,4-Di-tert-butylphenol, a phosphite degradation product, was found at up to 45.6 mg/kg in biaxially oriented polypropylene and LDPE by Qian and colleagues in 2018, a polyolefin measurement rather than a PET one. How a sample is identified at all is set out on additive analysis and deformulation of plastics, and the study set is reviewed on chemicals migrating from plastic food packaging.

Do biodegradable additives work in PET?#

Five biodegradation-promoting additives were tested against polyethylene and PET by Selke and colleagues in 2015, and none produced a significant increase in biodegradation in compost, in anaerobic digestion or in soil. The law has moved the same way: oxo-degradable plastic products have been prohibited in the European Union since 3 July 2021 under Article 5 of Directive (EU) 2019/904, and FTC Green Guides 260.8 treat an unqualified degradable claim as deceptive unless the item decomposes within one year of customary disposal. The evidence for every pro-degradant type is on biodegradation additives for plastics.

How do additives affect PET recycling?#

The additives in a PET bottle decide whether the bottle can go back into a bottle: a reheat additive that darkens the flake, a barrier layer above the EPBP threshold or a scavenger that will not survive five loops each take the pack out of the clear bottle-to-bottle stream. The Association of Plastic Recyclers fails a dark flake at an L* below 40 or a near-infrared reflectance of 10 % or less. What comes back with the recyclate from older packaging is covered on legacy additives in recycled plastic.