BHT (Butylated Hydroxytoluene) as an Antioxidant for Plastics

BHT (butylated hydroxytoluene, CAS 128-37-0) is a low-molecular-weight hindered phenol used as a primary antioxidant in polymers, and at 220.35 g/mol it is the lightest of the phenolic stabilizers in commercial use. That low molecular weight is also the reason BHT has disappeared from most polyolefin compounds, which raises the question of where it is still the right choice. Its molecular formula is C15H24O and its systematic name 2,6-di-tert-butyl-4-methylphenol.

BHT is authorised for EU food-contact plastics as FCM substance 315 under Regulation (EU) No 10/2011 with a specific migration limit of 3 mg/kg, prior-sanctioned for US food packaging under 21 CFR 181.24, and registered under REACH without being a Substance of Very High Concern, while a REACH substance evaluation for suspected endocrine disruption and the FDA post-market reassessment opened on 13 May 2026 both remain unfinished. BHT is one of 43 antioxidant pages in our directory of plastic additives, each with the same identity, dosage and regulatory fields.

Four facts organise everything below: the phenolic O-H interrupts autoxidation at its propagation step, 220.35 g/mol against 531 and 1,178 g/mol decides how much stabilizer survives compounding, 4 polymer systems still specify BHT despite its gas-fading and VOC penalties, and Irganox 1076, Irganox 1010 and vitamin E carry the volume it lost.

The identity table below collects the numbers a specification, a customs declaration and a food-contact declaration ask for.

What Is BHT (Butylated Hydroxytoluene)?#

BHT is 2,6-di-tert-butyl-4-methylphenol, a hindered phenol whose two bulky tert-butyl groups sit either side of the phenolic O-H and let that O-H give up a hydrogen atom to a peroxy radical without starting a new chain. The two ortho tert-butyl groups do two jobs at once: they shield the oxygen sterically, and they spread the unpaired electron of the phenoxy radical left behind across the aromatic ring. That resonance stabilization turns a phenol into a radical trap, and it is why hindered phenols form the chain-breaking class of antioxidants for plastics rather than the hydroperoxide-decomposing class.

Molecular weight is where BHT separates from the rest of that class. Primary antioxidants generally sit between 300 and 1,000 g/mol, and BHT at 220.35 g/mol falls below the band, which is the single property that explains its processing behaviour, its migration behaviour and its decline in tonnage. As a primary antioxidant, BHT belongs to the chain-breaking half of the family; the hub on antioxidants for plastics compares the primary, secondary and carbon-radical classes and shows which job each one takes inside a formulation. Why does the industry also call this molecule antioxidant 264?

What does BHT stand for, and what is antioxidant 264?#

BHT stands for butylated hydroxytoluene, and in the Asian generic naming system the same substance is sold as antioxidant 264. That number is a trade convention rather than a chemical code, and unlike 1010 or 1076 it matches no Irganox grade. Four further synonyms describe the same CAS number 128-37-0: the systematic name 2,6-di-tert-butyl-4-methylphenol, the older 2,6-di-tert-butyl-p-cresol, the abbreviation DBPC and the EU food additive number E321, and suppliers add their own trade names, among them Ionol, Topanol O and OC, Tenox BHT, Sustane BHT, Vulkanox KB and Sumilizer BHT. Equivalent grade names across suppliers are resolved in the plastic additive trade name lookup.

Is BHT the same as BHA?#

No: BHT (butylated hydroxytoluene, CAS 128-37-0) and BHA (butylated hydroxyanisole) are different substances, and the difference matters in California, because BHA is on the Proposition 65 list and BHT is not. Both are named in the same US prior-sanctioned list for food packaging, 21 CFR 181.24, which is where the habit of writing "BHA and BHT" as a single item comes from. Carried into a hazard statement, that habit produces the most frequent factual error made about BHT in plastics.

How Does BHT Work as an Antioxidant in Polymers?#

BHT works as a chain-breaking antioxidant: its phenolic O-H donates a hydrogen atom to a peroxy radical (ROO• + ArOH → ROOH + ArO•), which stops that radical from abstracting a hydrogen from the polymer chain. Each hydrogen atom transfer converts a propagating peroxy radical into a hydroperoxide, a species that no longer attacks the chain directly, and converts BHT into a phenoxy radical. The antioxidant is consumed sacrificially in that step, so the protection built into a compound is finite and falls with every processing pass, every regrind and every hour at service temperature. What happens to the phenoxy radical that is left behind?

The phenoxy radical is resonance-stabilized by the two ortho tert-butyl groups, is too hindered to pull hydrogen out of the polymer, and ends as non-radical products, typically quinone methides. Quinone methides are colour bodies, which is why BHT can tint a white compound while it does its job. The hydrogen-transfer step is shared by every one of the phenolic antioxidants (hindered phenols), which differ from one another only in the anchor that carries the phenol head.

Which degradation cycle does BHT interrupt?#

BHT interrupts the autoxidation cycle at the propagation step, the stage in the Bolland-Gee scheme where a peroxy radical pulls a hydrogen atom from the polymer and creates a new alkyl radical. The basic scheme, set out by J. L. Bolland and G. Gee at the British Rubber Producers' Research Association in the 1940s, runs in the 4 steps listed below.

1. Initiation: heat or shear splits a bond (R-R → 2 R•), and each alkyl radical adds oxygen (R• + O2 → ROO•).
2. Propagation: the peroxy radical abstracts hydrogen from a neighbouring chain (ROO• + RH → ROOH + R•), which regenerates an alkyl radical and closes the loop.
3. Chain branching: the hydroperoxide splits (ROOH → RO• + •OH), so one hydroperoxide yields two new radicals and the reaction turns autocatalytic.
4. Termination: radicals combine to non-radical products, which is slow while oxygen remains available.

Autocatalysis gives oxygen uptake its sigmoidal shape, with an induction period followed by a steep climb, and a chain-breaking antioxidant works by extending that induction period. The alkyl radical of step 1 is the hardest target in the cycle, because R• + O2 runs at a diffusion-controlled 10^7 to 10^9 L mol-1 s-1, which is why lactones, hydroxylamines and acrylated phenols exist as a separate carbon-radical scavenger class beside the phenols. The 4 steps and their rate constants are set out on polymer oxidation and antioxidant mechanisms.

How many radicals does one BHT molecule trap?#

One hindered phenol traps about 2 peroxyl radicals, a stoichiometric factor measured for alpha-tocopherol, PMHC, BHA and BHT. Rate constants are a different matter. In a 2004 Chemistry and Physics of Lipids study that followed methyl methacrylate polymerisation at 70 °C by differential scanning calorimetry, BHT inhibited growing PMMA radicals with a rate constant of (1-2) x 10^3 M^-1 s^-1 and an n value of 1 to 2. That measurement was made against carbon-centred radicals rather than peroxy radicals, so it cannot be quoted as a peroxyl rate constant, and the higher BHT rate constant that circulates in secondary sources is not supported by the primary literature checked for this page.

What Are the Physical and Chemical Properties of BHT?#

BHT is a white crystalline solid with a melting point of 70 to 71 °C (158 to 159.8 °F) and a molecular weight of 220.35 g/mol. The verified property set is listed below.

Boiling point, flash point, vapour pressure, density and solubility are not part of our verified data set; see the methodology page.

That melting point matters more than it looks. Plastics melt processing runs from 150 to 320 °C, so BHT is liquid from the first metre of the extruder barrel and stays at least 80 °C above its melting point even in the coolest compounding job, which puts it in the temperature region where a 220 g/mol molecule evaporates from the melt and from the die face rather than staying in the polymer.

Why is BHT volatile? Molecular weight 220 against 531 and 1,178#

BHT is volatile because it is small: at 220.35 g/mol it sits below the 300 to 1,000 g/mol band that primary antioxidants normally occupy, and molecular weight is the single property that governs how much stabilizer survives compounding. Commercial phenols are built on exactly that insight. The same active head, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, is attached to anchors of increasing weight: BHT carries none, Irganox 1076 carries an octadecyl ester at 531 g/mol, Irganox 1330 reaches 775 g/mol, Irganox 3114 reaches 784 g/mol on an isocyanurate ring, and Irganox 1010 reaches 1,178 g/mol on a pentaerythritol core. How much difference does the molecular weight actually make?

Three orders of magnitude, where the numbers exist. Irganox 1076 has a vapour pressure of 2.5E-7 Pa at 20 °C and Irganox 1010 about 7E-10 Pa, while no measured vapour pressure for BHT is held in our data set. Higher molecular weight buys lower volatility and lower extraction, and it costs diffusion rate, so the heavy phenols move more slowly to the oxidising surface of a part. Molecular weight, vapour pressure and diffusion together decide additive volatility, extraction and fogging for every additive class.

The two vapour-pressure values come from the Irganox 1076 supplier data sheet and our antioxidants dossier; the blanks are gaps in the data set, not zeros.

Which Polymers Use BHT, and at What Level?#

BHT is no longer a general-purpose polyolefin stabilizer: it survives today in 4 systems, namely in-process stabilisation of monomers and polymers, PVC tin stabilizer formulations, polyols and polyurethane foam, and rubber and adhesive compounds. High volatility is the reason for the retreat, and higher-molecular-weight phenols such as Irganox 1076 took the ground it lost in most plastics. The table below records the role BHT plays in each system and the evidence behind it.

No typical loading in phr or wt% for BHT is held in our verified data set, and the single percentage above is a legal maximum inside one FDA-listed formulation, not a recommended dosage. Typical loading ranges for every additive family are collected on additive dosage levels in plastics.

BHT in PVC stabiliser formulations#

In PVC, BHT is a co-stabilizer rather than the main stabilizer: US food-contact law allows it only as an optional constituent at up to 5 % of one methyltin-2-mercaptoethyloleate sulfide formulation for rigid PVC water pipes and fittings (21 CFR 178.2010). The primary work in PVC is done by the heat stabilizer, which neutralises the hydrogen chloride that the polymer releases on heating, and antioxidants only assist that system. The formulation BHT sits inside is a methyltin system, one of the organotin stabilizers used for rigid PVC pipe.

That 5 % figure is a ceiling written into a food-contact clearance and carries no information about what a compounder actually adds. A rigid pipe recipe pairs the tin stabilizer with lubricants, fillers and impact modifiers, as set out in additives for PVC.

BHT in polyols and polyurethane foam#

Polyurethane is the clearest case of BHT being designed out: the standard polyol package is a liquid phenol such as Irganox 1135 with a liquid aminic such as Irganox 5057 at 0.1 to 0.4 %, and these systems are specified BHT-free because BHT evaporates and contributes to fogging. The job the package has to do is scorch protection, scorch being the core discolouration of flexible slabstock foam driven by the exotherm of the isocyanate and water reaction. A volatile phenol is a poor fit for that duty, because the antioxidant has to stay in the polyol through storage and through the foaming exotherm. Scorch protection packages for flexible slabstock foam are compared on antioxidants for polyurethane.

BHT in rubber and adhesives#

BHT also serves as an antioxidant in rubber compounds and adhesives, which is where the trade names Vulkanox KB and Sumilizer BHT come from. Elastomers sit inside the scope of this reference only where the same substance serves both plastics and rubber, as BHT does; where the same chemistry serves elastomers alone, it is covered under antioxidants and antiozonants for rubber.

BHT in polyolefins: why Irganox 1076 and 1010 took over#

Irganox 1076 and Irganox 1010 replaced BHT in polyolefins because they keep the same active hindered-phenol head and attach it to a much heavier anchor, which is what a melt process running at 150 to 320 °C demands. Higher molecular weight lowers both volatility and extraction, the two loss routes that decide how much antioxidant is still present when a part leaves the mould. US Chemical Data Reporting volumes for 2023 show the result as reported bands: Irganox 1010 at 40 to under 55 million lb, Irganox 1076 at 25 to under 40 million lb, and BHT at 2.5 to under 4 million lb, down from the 10 to 50 million lb band reported for 2020 and 2021. Current polypropylene packages are built from phenol and phosphite blends, as described on antioxidants for polypropylene.

What Is BHT Used For in Plastics?#

BHT has 4 remaining jobs in plastics, listed below in the order of the systems that still specify it.

• In-process stabilisation of monomers and polymers during production, protecting the material between reactor and pellet rather than over a service life.
• Storage and scorch protection of polyols before they are foamed, a duty that liquid phenol and aminic packages now take over.
• Co-stabilisation inside PVC tin stabilizer formulations, alongside the methyltin system that neutralises hydrogen chloride.
• Antioxidant duty in rubber and adhesive compounds, sold under names such as Vulkanox KB and Sumilizer BHT.

Every one of those 4 jobs shares a trait: the protection has to last hours, weeks or a single processing step rather than a decade in the sun. A stabilizer that evaporates during compounding cannot protect a water pipe, a garden chair or a bumper for 20 years, so long-service applications went to the heavy phenols. Short-term and in-process work for BHT, long-term work for Irganox 1076 and Irganox 1010: that division of labour is its position in plastics today.

How Does BHT Perform? Volatility, OIT and Discolouration#

BHT is the one phenolic antioxidant whose OIT result needs a caveat: ASTM D3895 states in Note 2 that volatile antioxidants can give poor oxidative induction times and still perform adequately at the intended use temperature. Oxidative induction time is measured by differential scanning calorimetry under ISO 11357-6:2018 and ASTM D3895, typically at 190 to 220 °C with a switch from nitrogen to oxygen, and at that temperature a 220.35 g/mol phenol is partly gone before the oxygen valve opens. So how should a compounder judge BHT?

By pairing the OIT run with a volatile-loss test and a colour check, because the losses that decide the outcome happen during processing and storage rather than in the DSC pan. ASTM D1203 measures volatile loss against activated carbon in two arrangements, Method A with the specimen in direct contact and Method B in a wire cage, and either one exposes what a short OIT hides. The DSC procedure behind these numbers is described on oxidative induction time (OIT).

Does BHT cause gas fading and pinking?#

Yes: nitrogen oxides in ambient air convert phenolic antioxidants into quinone methides, and from BHT they form stilbenequinone, a yellow to pink discolouration that typically appears in warehouses with gas-fired forklifts or heaters. White polypropylene fibre, film and thermoplastic polyolefin parts show the defect first, because there is no pigment to hide a pink cast. The full set of causes behind yellowing, pinking and gas fading covers NOx, overheating, metal traces and pigment reactions.

The remedy is chemical rather than procedural. Phenol-free stabilization, built from a hydroxylamine plus a phosphite, removes the species that NOx attacks, and N,N-dibenzylhydroxylamine is documented as preventing the gas fading of polypropylene stabilized with a phenolic antioxidant in US patent 4,590,231. Phenolics are also not recommended where parts pass through direct gas-fired ovens, a duty that falls to Irgafos 168. Where discolouration cannot be tolerated, compounders move to phenol-free stabilization.

Does BHT raise VOC and fogging values?#

Yes: low-molecular-weight phenolic antioxidants such as BHT raise both VOC emissions and fogging values in vehicle interiors, which is why automotive interior specifications drive compounders towards high-molecular-weight antioxidants such as Irganox 1010. BHT is named in the testing literature as a notorious fogging and VOC source, and the two methods that decide this are covered on fogging and VOC testing: DIN 75201 for fogging, and VDA 278 with thermal desorption at 90 °C for 30 minutes and GC-MS quantification in toluene equivalents.

Odour is judged separately by VDA 270, which holds samples at 80 °C for 2 hours before a panel of 4 to 6 assessors grading 1 to 6. Interior specifications drive the whole additive package, as set out on additives for automotive interiors.

How Does BHT Interact with Other Additives?#

BHT is combined rather than used alone: it pairs with a phosphite as the hydroperoxide decomposer, with a thioester for long-term heat ageing at about 100 to 150 °C, and inside PVC with the organotin or mixed-metal stabilizer that does the primary work. The 3 combinations that govern its use are listed below.

• Phenol with phosphite, the standard processing pair, in phenol to phosphite weight ratios that run from about 20:1 to 1:10 across the patent literature.
• Phenol with thioester, effective for long-term heat ageing at about 100 to 150 °C rather than in the melt, and antagonistic with hindered amine light stabilizers, whose acidic sulfur oxidation products deactivate the HALS.
• Phenol with a PVC heat stabilizer, where the antioxidant is a co-stabilizer and the metal system carries the hydrogen chloride load.

Phenol, phosphite, thioester and HALS combinations are mapped on additive interactions: synergy and antagonism. One BHT-specific interaction is recorded in our formulation matrix: BHT combined with the NOR hindered amine NOR 371 is reported in the NOR 371 supplier data sheet as causing discolouration in the dark, a single-source observation rather than a general rule.

Ready-made ratios are sold as blends, which are listed on antioxidant blends and synergy. BHT does not appear in those commercial blends, and that absence is informative: the blend business is built on Irganox 1010, Irganox 1076 and Irgafos 168.

What Is the Regulatory Status of BHT?#

BHT is REACH-registered, is not a Substance of Very High Concern, is authorised for EU food-contact plastics as FCM substance 315 with a specific migration limit of 3 mg/kg, and is prior-sanctioned in the United States under 21 CFR 181.24, while remaining under both a REACH substance evaluation and an FDA post-market reassessment (status 23 September 2026). The matrix below states each instrument separately, because the answer differs by jurisdiction and by use.

Two of those rows are processes rather than states, and both belong to REACH: registration is complete, while evaluation is not. Registration, evaluation and the CoRAP process are explained on REACH and plastic additives.

Is BHT REACH registered, and is it an SVHC?#

Yes, BHT is registered under REACH (Regulation (EC) No 1907/2006), and no, it is not a Substance of Very High Concern: it is absent from the Candidate List as of 23 September 2026. The registration dossier is held at ECHA under dossier number 15975, and the substance record carries the identifier 100.004.439.

A CoRAP entry is a different signal from a Candidate List entry. The Community Rolling Action Plan schedules a substance for evaluation by a Member State authority, and where the concern is endocrine disruption, that evaluation is the step that can precede an Article 57(f) proposal. BHT also appears on the European Commission's 2019 cosmetics endocrine-disruptor priority list and on EDlists List II, the list of substances under EU investigation for endocrine-disrupting properties. No Article 57(f) proposal for BHT has been published in the sources checked for this page. Antioxidant 2246 and TNPP are on the SVHC Candidate List; BHT has never been added.

Is BHT allowed in food-contact plastics?#

Yes: BHT is listed in Annex I of Regulation (EU) No 10/2011 as FCM substance 315 with a specific migration limit of 3 mg/kg, twenty times lower than the generic 60 mg/kg limit that applies where no substance-specific value exists. The entry carries Ref 46640, and the fat reduction factor does not apply to it. Alongside the specific limit, the overall migration limit of 10 mg/dm2 applies to the finished article, expressed as 60 mg/kg for materials intended for infants and young children. How FCM numbers, SMLs and the overall migration limit fit together is explained on EU 10/2011.

In the United States BHT is prior-sanctioned rather than newly authorised: 21 CFR 181.24 lists it among 9 antioxidants that may migrate from packaging, alongside BHA, DLTDP, DSTDP, gum guaiac, NDGA, propyl gallate, thiodipropionic acid and 2,4,5-trihydroxybutyrophenone, with a limit of addition to food of 0.005 %. The polymer clearance is narrower still. Every antioxidant cleared for US food-contact polymers, with its percentage cap, is listed on 21 CFR 178.2010, and BHT appears there only inside the methyltin stabilizer formulation described above. The full SML table for the family sits on food contact antioxidants.

Is BHT listed under California Proposition 65?#

No, BHT is not on the California Proposition 65 list, although butylated hydroxyanisole (BHA) is, which is the single most common factual error on consumer pages that treat BHA and BHT as one chemical. Listing dates for every listed plastic additive are on California Proposition 65.

What is the FDA doing about BHT in 2026?#

The FDA opened a post-market reassessment of BHT on 13 May 2026, publishing a Request for Information on BHT in food and as a food contact substance under docket FDA-2026-N-2526. The original comment deadline of 13 July 2026 was reopened to 31 August 2026 by a Federal Register notice of 30 July 2026, and no conclusion appears in the sources checked as of 23 September 2026.

A Request for Information gathers data; it does not restrict a substance, and the authorisations in 21 CFR 181.24 and 21 CFR 178.2010 remain in force while the docket is open. BHT sits alongside 4 other entries in the agency's post-market programme: azodicarbonamide under docket FDA-2026-N-4126, the BPA petition under docket FDA-2022-F-1108, fluorinated HDPE containers, and titanium dioxide under review since 4 March 2024, while the Irgafos 168 review concluded on 17 June 2023 with a safe outcome. Prior sanction, GRAS, FCN and threshold-of-regulation routes are distinguished on FDA food contact rules for plastic additives.

Is BHT Safe? Hazard Classification and the Endocrine Question#

BHT has no harmonised hazard classification under the EU CLP Regulation (EC) No 1272/2008, and the hazard statements that appear on safety data sheets are self-classifications: most companies notifying BHT to ECHA report H400 and H410 for aquatic toxicity, and a minority report H302, H361 and H373. The 3 elements of its current status are listed below.

• Classification: no harmonised entry in Annex VI of the CLP Regulation, so every hazard statement on a supplier document is that supplier's own notified classification.
• Evaluation: a REACH substance evaluation for suspected endocrine disruption is open, BHT appears on EDlists List II, and the Commission placed it on the 2019 cosmetics endocrine-disruptor priority list. In the cosmetics domain, the Scientific Committee on Consumer Safety found BHT safe up to 0.8 %, a conclusion that applies to cosmetic products and not to polymers.
• Exposure: synthetic phenolic antioxidants measured in Chinese food-contact materials summed to 44.18 to 69,485.12 µg/kg with a median of 2,615.63 µg/kg, with 2,4-DTBP, 2,6-DTBP and BHT-quinone among the dominant species (PubMed 38788569).

No LD50, no NOAEL and no carcinogenicity conclusion for BHT is held in our verified data set, and none is asserted here. The open question has a precise shape: BHT is under evaluation as one of the suspected endocrine disruptors in plastics, with no EU conclusion published and no restriction in force.

Is BHT banned?#

No: BHT is not banned in the EU or the United States, and for plastics it is explicitly authorised, listed as FCM substance 315 in Regulation (EU) No 10/2011 with a specific migration limit of 3 mg/kg and prior-sanctioned for food packaging under 21 CFR 181.24. Two processes are open at the same time, and neither is a restriction: the REACH substance evaluation for suspected endocrine disruption, and the FDA Request for Information published on 13 May 2026. The additives that do carry restrictions are listed on toxic plastic additives; BHT is not among them. Rules for cosmetics in individual countries sit outside the scope of this page, which covers BHT in plastics.

What Can Replace BHT in Plastics?#

BHT has 3 established substitutes in plastics: Irganox 1076 for polyolefins, Irganox 1010 where the lowest volatility is required, and vitamin E (alpha-tocopherol) where a bio-based melt stabilizer is wanted. The table compares the 4 grades on the fields that decide a substitution.

FDA percentages are legal maxima, not recommended dosages.

Grade-by-grade data, including Irganox 1010 against BHT, sit on the antioxidant grade comparison.

BHT vs Irganox 1076#

Irganox 1076 is the direct replacement for BHT in polyolefins: it carries the same hindered-phenol head on an octadecyl ester anchor, which raises the molecular weight from 220.35 to 530.9 g/mol and the specific migration limit from 3 to 6 mg/kg. The substitution costs nothing in mechanism, because both molecules donate the same phenolic hydrogen to the same peroxy radical, and it buys a vapour pressure of 2.5E-7 Pa at 20 °C. Irganox 1076 (Antioxidant 1076) carries an SML of 6 mg/kg under FCM 433, is cleared under 21 CFR 178.2010 at up to 0.25 % in listed olefin polymers and polystyrene and 0.5 % in ABS, and is used at 0.1 to 0.4 wt% in polyolefins under supplier guidance.

BHT vs Irganox 1010#

Irganox 1010 is the opposite end of the same design: a tetra-functional phenol of 1,177.6 g/mol that carries four hindered-phenol heads on one pentaerythritol core, which is why it is the volume leader and BHT is not. Its vapour pressure of about 7E-10 Pa is three orders of magnitude below that of Irganox 1076, so it stays in thick sections for years. Irganox 1010 (Antioxidant 1010) is listed as FCM 496 with no individual SML, so only the overall migration limit applies, and US Chemical Data Reporting puts it at 40 to under 55 million lb for 2023 against 2.5 to under 4 million lb for BHT.

BHT vs vitamin E (alpha-tocopherol)#

Vitamin E is the bio-based answer to the same problem: alpha-tocopherol protects polyethylene and polypropylene melts at only 100 to 300 ppm, a fraction of the level a conventional phenol needs. Its molecular weight of 430.7 g/mol sits between BHT and Irganox 1076, and it is supplied either as the synthetic all-rac form (CAS 10191-41-0) or as the natural RRR form (CAS 59-02-9). The stoichiometric factor of about 2 peroxyl radicals per phenol applies to alpha-tocopherol as it does to BHT, but the peroxyl trapping rate constant of alpha-tocopherol is roughly three orders of magnitude higher than the value measured for BHT in the PMMA study above. Vitamin E (alpha-tocopherol) works at 100 to 300 ppm in polyethylene and polypropylene melts.

Who Makes BHT? Trade Names and Grades#

BHT is a commodity antioxidant sold under at least 6 trade names, among them Ionol, Topanol O and OC, Tenox BHT, Sustane BHT, Vulkanox KB and Sumilizer BHT. US production and import fell to a reported band of 2.5 to under 4 million lb in 2023 from the 10 to 50 million lb band reported for 2020 and 2021, while the EU registration sits in a tonnage band of 10,000 to 100,000 tonnes per year. Producers and their locations are compared in the directory of polymer antioxidant manufacturers.

No producer is recorded against BHT in our verified data set; the two brand attributions are inferred from sibling records and are being verified.

Buyers should request the supplier's technical data sheet and safety data sheet, the assay and volatiles specification, and a statement of the intended polymer system, because a food grade and a rubber grade of BHT differ in specification rather than in CAS number.

How Does BHT in Plastics Differ from BHT in Food and Cosmetics?#

The molecule is identical; the rule set is not: the same CAS number 128-37-0 is regulated as FCM substance 315 in plastics, as food additive E321 in the EU food chain, and as a GRAS substance under 21 CFR 182.3173 in the United States. Each of those systems asks a different question. Food-contact law asks how much migrates into food, which is why the plastics answer is a number in mg/kg. Food law asks how much is added to food deliberately. Cosmetics law asks about dermal exposure at a use concentration. The sections below mark those borders and return to the polymer case.

BHT as food additive E321#

In food, BHT carries the EU additive number E321 and, in the United States, GRAS status under 21 CFR 182.3173 plus a direct food additive listing under 21 CFR 172.115. Those are direct-addition rules, and they are separate from the packaging route, where 21 CFR 181.24 sets a limit of addition to food of 0.005 % for antioxidants migrating out of packaging material. Food formulation, permitted foods and use levels are outside the scope of this reference, which covers BHT as a polymer stabilizer.

BHT in cosmetics, rubber, fuels and lubricants#

Outside plastics, BHT is used in cosmetics, rubber compounds, adhesives and petroleum products, and each of those sits under a different rule set. The 3 that our data set documents are listed below.

• Cosmetics: the Scientific Committee on Consumer Safety found BHT safe up to 0.8 % in cosmetic products, and the European Commission placed BHT on its 2019 cosmetics endocrine-disruptor priority list.
• Rubber and adhesives: the same antioxidant function as in plastics, carried by the trade names Vulkanox KB and Sumilizer BHT.
• Fuels and lubricants: recorded as a use category only; no fuel or lubricant figures for BHT are held in our verified data set.

Inside plastics the bio-based route is covered on natural and bio-based antioxidants for plastics.

Does BHT migrate out of plastic packaging?#

BHT can migrate from packaging into food, which is exactly what the 3 mg/kg specific migration limit controls. A survey of Chinese food-contact materials indexed in PubMed under identifier 38788569, whose publication year is not yet confirmed in our data set, found synthetic phenolic antioxidants at summed concentrations of 44.18 to 69,485.12 µg/kg with a median of 2,615.63 µg/kg, BHT-quinone among the dominant species. Diffusion and partition drive additive migration in plastics for every low-molecular-weight additive, and BHT is at the light end of that group. Compliance is demonstrated by migration testing of plastics for food contact under Regulation (EU) No 10/2011 with EN 1186 and EN 13130, and under the FDA protocols in the United States.

What is the full form of BHT?#

The full form of BHT is butylated hydroxytoluene, whose systematic name is 2,6-di-tert-butyl-4-methylphenol. The same substance is also written as 2,6-di-tert-butyl-p-cresol, abbreviated DBPC, and numbered E321 in the EU food additive system.

Does BHT have an SDS, and what does it say?#

Yes: every BHT supplier issues a safety data sheet, and because BHT has no harmonised CLP classification, the hazard statements it carries are the supplier's own self-classification, most often H400 and H410 for aquatic toxicity. A minority of notifiers to ECHA also report H302, H361 and H373, so two safety data sheets for the same CAS number 128-37-0 can differ in their classification section.