A cyanoacrylate adhesive is a one-part adhesive based on an alkyl 2-cyanoacrylate monomer that polymerizes anionically when surface moisture meets the bond line, so parts fix in seconds and reach full chemical resistance after at least 24 hours. Among industrial adhesive chemicals, its formula holds four bottle ingredients at most: the monomer as the balance, an acidic and a free-radical stabilizer, an optional thickening polymer, and a separate accelerator applied to the part rather than to the bottle.
The four attributes in the title follow in that order: the chemistry of cure and composition, the grades and their data sheet values, the accelerators and primers that carry the chemistry into gaps and onto polyolefins, and the limits that send a joint to another adhesive family.
Fixture time is the time to 0.1 N/mm² (14.5 psi) shear strength, not full cure. A published patent example stabilizes 2-octyl cyanoacrylate with 100 ppm sulfur dioxide and 1,000 ppm butylated hydroxyanisole and thickens it to 567 cP with its own polymer. Polyethylene, polypropylene and PTFE bond only with a primer or a CA/epoxy hybrid. In the EU, ethyl and methyl 2-cyanoacrylate carry CLP Annex VI entries 607-236-00-9 and 607-235-00-3, and every cyanoacrylate adhesive carries EUH202 on its immediate packaging; in the US, SCAQMD Rule 1168 defines the cyanoacrylate adhesive and 21 CFR 878.4010 classifies medical tissue adhesives.
Sources and checks: identities and hazard classifications are read at ECHA and the issuing regulator, standards at the body that publishes them, and grade values at the data sheet named next to them; methodology and fact-checking explains each step.
What Is a Cyanoacrylate Adhesive?#
A cyanoacrylate (CA) adhesive, also sold as an instant adhesive, is a one-part reactive adhesive whose alkyl 2-cyanoacrylate monomer polymerizes in thin bond lines without mixing, heat or light. Super glue is the consumer term for the same chemistry. The answer to whether cyanoacrylate is just super glue is therefore chemical: the monomer family is the same, and industrial grades are specified by viscosity, fixture time on named substrates and service temperature on a dated data sheet.
Cyanoacrylates belong to the chemically curing adhesives, and within that group they are the one family that cures by anionic chain polymerization, against polyaddition for epoxy and polyurethane and radical chain polymerization for acrylic, anaerobic and UV acrylate adhesives. The abbreviation CA is ambiguous: it also stands for cellulose acetate and for California, so the full name comes first wherever the context is not clear. MCA is ambiguous in the same way, naming both methyl 2-cyanoacrylate and melamine cyanurate.
How Does a Cyanoacrylate Adhesive Cure?#
A cyanoacrylate adhesive cures by anionic polymerization that moisture or hydroxide ions on the substrate start without any added hardener. The nitrile (-CN) and ester (-COOEt) groups on one carbon pull electron density from the C=C double bond, so a weak base such as adsorbed water can attack that bond and start a growing chain, as a review indexed in PubMed Central (PMC12444979) describes.
Anionic chain polymerization sets cyanoacrylates apart from the other chemical cure routes. The comparison of how adhesives cure by evaporation, cooling, chemical reaction and radiation, with the open time each route allows, sits under how adhesives cure.
Cure speed follows the surface and the air. Higher relative humidity speeds cure, while acidic or dry surfaces and larger gaps slow it. Each effect follows from the initiation step, because the chain starts only where a weak base meets the monomer, and an acid neutralizes that base.
Fixture Time Versus Full Cure#
Fixture time is the time a cyanoacrylate bond needs to reach 0.1 N/mm² (0.1 MPa, 14.5 psi) shear strength at 22 °C (71.6 °F) and 50 % relative humidity, and it is not full cure. On that definition, LOCTITE 401 fixtures steel, aluminum, ABS, PVC and nitrile rubber in less than 5 seconds (typical product value, Henkel TDS February 2012).
Full chemical and solvent resistance arrives later, because cure continues for at least 24 hours after fixture. A fixtured part holds its position for handling and the next assembly step, while the resistance and strength values of a data sheet describe the fully cured bond. A cyanoacrylate is therefore never "fully cured in seconds"; it is fixtured in seconds.
What Are Cyanoacrylate Adhesives Made Of?#
Cyanoacrylate adhesives are made of an alkyl 2-cyanoacrylate monomer as the balance, an acidic stabilizer and a free-radical stabilizer for shelf life, and optionally a thickening polymer and a plasticizer, as set out in Chemence Medical patent US20130095262A2. The accelerator and the primer are separate products applied to the part, not ingredients of the bottle.
The table lists each cyanoacrylate raw material by function, with its example in the published formula where one exists.
| Function | Family hub | Substances | Example in a published formula |
|---|---|---|---|
| Base monomer (balance) | monomers for reactive adhesives | ethyl cyanoacrylate, methyl, n-butyl and 2-octyl cyanoacrylate | 2-octyl cyanoacrylate, balance (US20130095262A2, Example 1) |
| Acidic (anionic) stabilizer | none | sulfur dioxide, sulfonic acids, phosphoric acid, sulfuric acid | sulfur dioxide 100 ppm (Example 1) |
| Free-radical stabilizer | none | hydroquinone, catechol, 4-methoxyphenol (MEHQ), butylated hydroxyanisole (BHA) | BHA 1,000 ppm (Example 1) |
| Thickening polymer | none | polymer of the monomer | poly(2-octyl cyanoacrylate) 3.5 % (Example 1) |
| Plasticizer | plasticizers for adhesives | dimethyl sebacate, tricresyl phosphate, dioctyl adipate | not in Example 1 |
| Accelerator (applied to the part) | none | amine accelerators (N,N-dialkyl aniline derivative, US5561198A); organic disulfide | carrier ethyl acetate (US5561198A); acetone (LOCTITE SF 7452) |
| Activator and primer carrier | solvents in adhesives | acetone, ethyl acetate, isopropyl acetate | acetone (LOCTITE SF 7452); isopropyl acetate (LOCTITE SF 770) |
| Polyolefin primer | adhesion promoters | aliphatic amine | LOCTITE SF 770 |
Cyanoacrylate Monomers: Ethyl, Methyl, Butyl and Octyl Esters#
Ethyl 2-cyanoacrylate (ECA, CAS 7085-85-0, EC 230-391-5, C6H7NO2) is the base monomer of general-purpose cyanoacrylate adhesives, and methyl, n-butyl and 2-octyl esters serve metal bonding and medical grades. Methyl 2-cyanoacrylate (MCA, CAS 137-05-3, EC 205-275-2, C5H5NO2) carries the shortest ester group of the four. Permabond assigns methyl 2-cyanoacrylate to strong bonds on metals, n-butyl 2-cyanoacrylate to medical and veterinary adhesives and 2-octyl cyanoacrylate to medical adhesives (producer article, 2016).
The two longer esters are n-butyl 2-cyanoacrylate (n-BCA, CAS 6606-65-1, EC 229-552-2, C8H11NO2) and 2-octyl cyanoacrylate (2-OCA, CAS 133978-15-1, EC 700-845-1, C12H19NO2). Both are REACH registered, and neither has a CLP Annex VI entry, unlike the ethyl and methyl esters. Alkoxyalkyl cyanoacrylates complete the monomer list of US20130095262A2 as a fifth class.
Acidic and Free-Radical Stabilizers in Cyanoacrylates#
Acidic, or anionic, stabilizers hold off premature anionic cure in the bottle; the patent names sulfur dioxide (SO2), sulfonic acids, phosphoric acid and sulfuric acid as examples. Stabilizer content is the shelf-life lever. An acid that neutralizes stray base keeps the monomer liquid, and the same acid slows cure once the adhesive reaches the part.
Free-radical stabilizers, such as hydroquinone, catechol, 4-methoxyphenol (MEHQ) and butylated hydroxyanisole (BHA), inhibit radical polymerization during storage. Two classes are needed because the monomer can polymerize by both routes, and each class inhibits one of them. Example 1 of the patent pairs one of each class, sulfur dioxide with BHA, at the levels given in the starting formula below.
Thickeners and Plasticizers in Cyanoacrylate Adhesives#
A thickening polymer dissolved in the monomer raises viscosity; Example 1 of the patent uses poly(2-octyl cyanoacrylate), the polymer of its own monomer. A thickened grade is specified by its viscosity range at a stated shear rate and temperature, the form industrial data sheets use.
Plasticizers, such as dimethyl sebacate, tricresyl phosphate and dioctyl adipate, add flexibility to the cured film, which is otherwise brittle under impact or peel. Rubber-toughened ethyl grades address the same brittleness from the polymer side and appear in the grade-types comparison further down.
Cyanoacrylate Adhesive Formulation#
Cyanoacrylate adhesive formulation balances reactivity against shelf life: the formulator adds just enough acid and radical stabilizer to keep the monomer liquid in the bottle, then sets viscosity with a dissolved polymer, as in Example 1 of US20130095262A2. Bottle gelation from moisture is the failure this balance guards against, since water that enters the container starts the same anionic chain that bonds the part. Excess acid shows up on the line instead, as slower cure on the substrate.
A Published Cyanoacrylate Starting Formula#
The published cyanoacrylate starting formula is Example 1 of US20130095262A2: 2-octyl cyanoacrylate stabilized with sulfur dioxide and BHA and thickened with its own polymer, as listed in the table.
The table gives the components, amounts and functions of Example 1.
| Component | Amount | Function |
|---|---|---|
| 2-Octyl cyanoacrylate | balance | monomer |
| Sulfur dioxide | 100 ppm | acidic stabilizer |
| Butylated hydroxyanisole (BHA) | 1,000 ppm | free-radical stabilizer |
| Poly(2-octyl cyanoacrylate) | 3.5 % | thickener |
| Result: viscosity before sterilization | 567 cP (567 mPa·s) |
Source: US20130095262A2, Example 1 (Chemence Medical, priority 2004-09-17, published 2013-04-18, abandoned); patent example, not a recommendation.
Example 1 reports 567 cP (567 mPa·s) before sterilization, the point at which the patent measured it, because sterilization is part of the medical route the composition was written for.
This is a patent example for a medical 2-octyl composition, not a recommendation for an industrial grade. Industrial ethyl grades differ in monomer and viscosity: LOCTITE 406, an ethyl grade for plastics and rubber, measures 12 to 22 mPa·s and the surface-insensitive LOCTITE 401 measures 70 to 110 mPa·s, both by cone and plate at 3,000 s⁻¹ and 25 °C (77 °F) (typical product values, Henkel TDS February 2012). Viscosity is therefore a grade choice, while the monomer and stabilizer system define the chemistry.
How Each Component Moves Shelf Life, Viscosity and Flexibility#
Each component of a cyanoacrylate moves one property in one direction, and the table sets out that direction for the stabilizers, thickener, plasticizer, accelerator and primer.
| Component | Raising its share or using it |
|---|---|
| Acidic stabilizer | longer shelf life against bottle gelation; slower cure on the part |
| Free-radical stabilizer | inhibits radical polymerization in storage |
| Thickening polymer | higher viscosity (3.5 % gives 567 cP in Example 1) |
| Plasticizer | more flexibility in the cured film |
| Accelerator applied to the part | faster cure in gaps and on dry surfaces; can reduce ultimate strength |
| Primer (aliphatic amine) | bonds PE, PP, PTFE and TPE; not for high-peel joints |
Read the table as two opposed pairs. The acid trades shelf life against cure speed on the part, and the accelerator trades cure speed against ultimate strength, so neither lever improves one property without costing another.
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Cyanoacrylate Accelerators, Activators and Primers#
Cyanoacrylate accelerators, also called activators, are solvent solutions of a base that start anionic cure on the part, while primers, such as aliphatic amines in solvent, prepare polyolefins for bonding. Both go onto the substrate and never into the bottle, since a base inside the container would start the same chain that causes bottle gelation. The solvent carries the active chemistry to the surface and then evaporates.
The table compares one activator and one primer by chemistry, carrier, drying time and on-part life.
| Product (producer, data sheet date) | Type | Active chemistry and carrier | Drying time | On-part life | Further data sheet values |
|---|---|---|---|---|---|
| LOCTITE SF 7452 (Henkel, page read 2026-11-02) | activator, applied after the adhesive | organic disulfide in acetone | 30 s | 5 min | used for wire tacking in electronics |
| LOCTITE SF 770 (Henkel, TDS May 2021) | polyolefin primer | aliphatic amine in isopropyl acetate | 8 to 9 s (steel and PP 9 s, PE 8 s) | 8 h | viscosity 0.62 mPa·s; PP block shear 15 N/mm² (2,200 psi) with LOCTITE 406, ISO 13445, cured 24 h at 23 °C / 50 % RH; not recommended where high peel strength is required |
How Does a Cyanoacrylate Accelerator Work?#
A cyanoacrylate accelerator works by leaving a weak base on the surface, which starts anionic polymerization where moisture alone is too slow: in large gaps and on dry or acidic surfaces. The solvent leaves within the drying time, and the base stays active only for the on-part life, so the adhesive has to follow inside that window.
Amine chemistry is the second accelerator route next to the organic disulfide in the table. US patent 5,561,198 A, assigned to Henkel, uses an N,N-dialkyl aniline derivative dissolved in ethyl acetate as the cyanoacrylate activator.
Speed has a price: the LOCTITE 401 data sheet notes that activators speed cure but can reduce ultimate strength. An accelerated joint therefore trades some strength for fixture in a gap or on a dry part, the trade the component table records.
Polyolefin Primers for Cyanoacrylate Bonding#
Polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE) and thermoplastic elastomers (TPE) need a primer before a cyanoacrylate bonds them. The aliphatic-amine primer in the table dries in seconds and leaves the surface ready for hours, so priming can run as its own station ahead of bonding.
Surface preparation for bonding decides the result on these plastics. Primed polypropylene reaches the block shear value in the table, so the primer, not the adhesive, carries the polyolefin case; the corona, plasma, flame, primer and abrasion routes are compared under surface preparation for bonding.
The primer carries one stated limit: it is not recommended where high peel strength is required, which matches the brittleness of cured cyanoacrylate under peel. Polyolefin joints that see peel move to the CA/epoxy hybrid or to another chemistry, as the selection table below shows.
Properties of Cyanoacrylate Adhesives#
Cyanoacrylate adhesives are characterized by fixture time, viscosity, shear and tensile strength, gap capability and service temperature, and every value on a data sheet is a typical product value of one named grade. A data sheet value is measured under stated conditions of temperature, humidity, substrate, cure time and method. It describes that grade only and never sets a requirement for the class.
Strength Values from Cyanoacrylate Data Sheets#
Cyanoacrylate strength values on data sheets cover lap shear and tensile strength on named substrates, and the table lists three of them with grade, substrate, cure and method.
| Property | Value | Substrate and cure | Method as cited | Grade (producer, data sheet date) |
|---|---|---|---|---|
| Lap shear strength | 20 N/mm² (2,900 psi) | grit-blasted steel | ISO 4587 | LOCTITE 401 (Henkel, TDS February 2012) |
| Lap shear strength | 15.5 N/mm² (2,250 psi) | grit-blasted steel, after 24 h | ISO 4587 | LOCTITE 406 (Henkel, TDS February 2012) |
| Tensile strength | at least 6.9 N/mm² (1,000 psi), product specification | Buna-N (nitrile rubber), after 10 s | ISO 6922 (withdrawn) | LOCTITE 401 and 406 (Henkel, TDS February 2012) |
The tensile row differs in kind from the two lap shear rows. It is a product specification, a minimum the grade must meet after 10 seconds on nitrile rubber, while the lap shear values are typical results.
Lap shear on grit-blasted steel is a rigid-to-rigid test, so these values describe metal joints rather than the rubber and plastic parts that fixture fastest. The primed polypropylene value in the accelerator table comes from a different test again, block shear, and is not comparable with lap shear.
Service Temperature and Environmental Resistance#
Cyanoacrylate service temperature ranges from 85 °C (185 °F) to 250 °C (480 °F) across cyanoacrylate types, according to a 2016 Permabond producer article. The range spans types, not one grade, so the data sheet of the chosen grade sets the limit for a given joint.
Water and polar solvents are the weak side: cured cyanoacrylate degrades by hydrolysis and in polar solvents, which limits it in wet service. The CA/epoxy hybrid LOCTITE HY 4090 reaches a glass transition temperature of 88 °C (190.4 °F) (typical product value, Henkel TDS July 2019). Service temperature is not the same quantity as glass transition temperature, so neither value stands in for the other.
Which Substrates Do Cyanoacrylate Adhesives Bond?#
Cyanoacrylate adhesives bond steel, aluminum, nitrile and neoprene rubbers, ABS, PVC, polycarbonate and phenolic directly, porous wood, paper, leather and fabric with surface-insensitive grades, and PE, PP, PTFE and TPE only with a primer.
The four substrate groups are listed below.
- Metals and rigid plastics, bonded directly: steel, aluminum, ABS, PVC, polycarbonate and phenolic.
- Rubbers, bonded directly: nitrile and neoprene.
- Porous substrates, bonded with surface-insensitive grades: wood, paper, leather and fabric.
- Low-energy plastics, bonded only after a primer: PE, PP, PTFE and TPE.
Low-energy plastics resist bonding because their low surface free energy keeps the liquid adhesive from wetting them; PE, PP and PTFE are the named cases, and no standard threshold defines the class. The physics of wetting and why low-energy plastics resist bonding are set out on the surface energy page.
Acidic or dry surfaces slow cure even on bondable materials. So a cyanoacrylate does bond plastic, provided the plastic is one of the directly bondable types or has been primed, and the selection table shows which route fits each plastic.
Cyanoacrylate Application Window: Humidity, Gap and Storage#
Cyanoacrylate adhesives are applied at room temperature in thin bond lines, with data sheets reporting fixture at 22 °C (71.6 °F) and 50 % relative humidity, because larger gaps slow cure and higher humidity speeds it. Humidity moves the line as well, so fixture times measured at that humidity do not transfer unchanged to drier or more humid air. For gaps beyond a thin film, the two-part cyanoacrylate gel LOCTITE 3090 fills up to 5 mm (0.2 in) with an open time of 90 to 180 seconds (product claim and typical product value, Henkel TDS September 2012).
Storage is part of the window. Unopened containers are stored at 2 to 8 °C (35.6 to 46.4 °F) according to the LOCTITE 401 data sheet, and moisture that enters an opened bottle causes bottle gelation, the anionic cure started in the wrong place. Stabilizer content sets how long the liquid resists that gelation, which links storage back to the formulation balance above.
How Are Cyanoacrylate Adhesives Tested?#
Cyanoacrylate adhesives are tested for fixture time, lap shear, block shear and tensile strength, viscosity and VOC content, and data sheets cite ISO 4587, ISO 13445 and ISO 6922 for the strength values.
The table gives each property with the method as cited, the document that cites it and the page that covers the method.
| Property | Method as cited | Source of the citation | Method page |
|---|---|---|---|
| Fixture time | time to 0.1 N/mm² at 22 °C / 50 % RH | LOCTITE 401 TDS (Henkel, February 2012) | none |
| Lap shear, rigid to rigid | ISO 4587 (current edition ISO 4587:2003) | LOCTITE 401 TDS | lap shear strength testing |
| Block shear | ISO 13445 (current edition ISO 13445:2003) | LOCTITE SF 770 TDS (Henkel, May 2021) | none |
| Tensile, butt joint | ISO 6922 (ISO 6922:1987, withdrawn 2008-03-17) | LOCTITE 401 and 406 TDS | none |
| Viscosity | cone and plate at 3,000 s⁻¹, 25 °C | LOCTITE 401 and 406 TDS | adhesive viscosity |
| US federal description | Commercial Item Description A-A-3097 | LOCTITE 406 TDS | none |
| VOC content | SCAQMD Method 316B | SCAQMD Rule 1168 | none |
Two of the three ISO strength methods are current: ISO 4587:2003 and ISO 13445:2003 are valid in the catalogue of the Estonian national standards body (EVS), while ISO 6922:1987 was withdrawn on 17 March 2008 with no successor listed. ISO 6922 therefore survives only as a citation, withdrawn but still cited on data sheets such as the LOCTITE 401 and 406 sheets of February 2012.
The LOCTITE 406 data sheet also cites Commercial Item Description A-A-3097, the US federal purchase description for cyanoacrylate adhesives. For VOC content, Rule 1168 assigns SCAQMD Method 316B to cyanoacrylates, separate from the EPA Method 24 route used for other adhesive types.
Regulation of Cyanoacrylate Adhesives#
Three rule sets govern industrial cyanoacrylate adhesives: EU hazard labeling, with the mandatory cyanoacrylate packaging phrase, US VOC rules such as SCAQMD Rule 1168, and US device rules for medical cyanoacrylates.
SCAQMD Rule 1168 (amended November 4, 2022; amendments proposed for a 4 December 2026 hearing) defines the cyanoacrylate adhesive for VOC purposes, one entry within the wider VOC limits for industrial adhesives covered under VOC limits for industrial adhesives.
The table gives the hazard line of each cyanoacrylate raw material and the packaging phrase of the finished adhesive.
| Substance | CAS (EC) | Hazard line |
|---|---|---|
| Ethyl 2-cyanoacrylate | 7085-85-0 (EC 230-391-5) | Annex VI 607-236-00-9: Eye Irrit. 2 H319, STOT SE 3 H335 (SCL C ≥ 10 %), Skin Irrit. 2 H315; Warning |
| Methyl 2-cyanoacrylate | 137-05-3 (EC 205-275-2) | Annex VI 607-235-00-3: Skin Irrit. 2 H315, Eye Irrit. 2 H319, STOT SE 3 H335 (SCL C ≥ 10 %); Warning |
| n-Butyl 2-cyanoacrylate | 6606-65-1 (EC 229-552-2) | No Annex VI entry |
| 2-Octyl cyanoacrylate | 133978-15-1 (EC 700-845-1) | No Annex VI entry |
| Sulfur dioxide (stabilizer) | 7446-09-5 (EC 231-195-2) | Annex VI 016-011-00-9: Skin Corr. 1B H314, Acute Tox. 3 H331, STOT SE 1 H370; Danger |
| 4-Methoxyphenol (MEHQ, stabilizer) | 150-76-5 (EC 205-769-8) | Annex VI 604-044-00-7: Acute Tox. 4* H302, Skin Sens. 1 H317, Eye Irrit. 2 H319; Warning |
| Cyanoacrylate adhesives (mixtures) | n/a | EUH202 "Cyanoacrylate. Danger. Bonds skin and eyes in seconds. Keep out of the reach of children" on the immediate packaging (CLP Annex II Part 2 point 2.2) |
EU Labeling: Annex VI Lines and the Cyanoacrylate Packaging Phrase#
Ethyl 2-cyanoacrylate (index 607-236-00-9) and methyl 2-cyanoacrylate (607-235-00-3) carry the same harmonized CLP Annex VI classification: Skin Irrit. 2 H315, Eye Irrit. 2 H319 and STOT SE 3 H335, with a 10 % concentration limit for H335. Both are original CLP entries, in application since 2010-12-01. n-Butyl and 2-octyl cyanoacrylate have no Annex VI entry.
Every adhesive based on cyanoacrylate carries EUH202 on its immediate packaging under CLP Annex II Part 2 point 2.2 (Regulation (EC) No 1272/2008, consolidated text 02008R1272-20260701): "Cyanoacrylate. Danger. Bonds skin and eyes in seconds. Keep out of the reach of children". The phrase follows the mixture type, so it applies to n-butyl and 2-octyl adhesives as well, and appropriate safety advice accompanies the package.
Ethyl 2-cyanoacrylate is REACH registered, is not on the Candidate List (253 entries, checked 2026-10-27), is not in Annex XIV and has no Annex XVII entry by name or CAS. Hazard labeling for adhesives, including the other adhesive-specific EUH phrases and the safety data sheet, is covered under hazard labeling for adhesives.
US Rules: VOC, Food Contact and Exposure Limits#
US rules reach cyanoacrylate adhesives at three points: the SCAQMD Rule 1168 VOC definition, the 21 CFR food-contact listings and the NIOSH exposure limit for methyl 2-cyanoacrylate. Rule 1168 defines a cyanoacrylate adhesive in (c)(26) as "an acrylic adhesive that contains ethyl, methyl, methoxymethyl or other functional groupings of cyanoacrylate". VOC content is determined by SCAQMD Method 316B, and Table 1 of the 2022 text has no separate cyanoacrylate category.
For worker exposure, NIOSH recommends 2 ppm (8 mg/m³) as an 8-hour time-weighted average and 4 ppm (16 mg/m³) as a short-term limit for methyl 2-cyanoacrylate (NIOSH Pocket Guide, read 2026-11-02). In California, the stabilizer sulfur dioxide is on the Proposition 65 list for developmental toxicity, listed 2011-07-29 (OEHHA list dated 2026-07-31). Ethyl 2-cyanoacrylate is active on the TSCA Inventory (EPA Substance Registry Services, checked 2026-10-27).
For food contact, 21 CFR 175.105(c)(5) names no cyanoacrylate among its listed adhesive components (eCFR, read 2026-10-23). The listings and conditions of use of food-contact adhesives, including the functional barrier and the trace amounts at seams that 21 CFR 175.105 allows, are covered under food-contact adhesives.
How to Choose a Cyanoacrylate Adhesive#
Choose a cyanoacrylate adhesive by substrate first, then by gap, load and service temperature, and move to an epoxy or structural acrylic where the joint sees peel, impact or water. Within cyanoacrylates, surface-insensitive ethyl grades cover fast fixture on mixed parts, a primer or a CA/epoxy hybrid covers polyolefins, and a two-part gel covers gaps up to 5 mm (0.2 in).
The order matters because each later criterion only narrows a choice the substrate has already made. No gap fill or temperature rating rescues an unprimed polypropylene joint, and no primer makes a brittle film suitable for peel. Medical skin closure is a separate route under 21 CFR 878.4010, not an industrial grade choice. The selection table pairs each requirement with the cyanoacrylate type and the dated evidence behind it.
| Requirement | Cyanoacrylate type | Evidence (grade, producer, data sheet date) |
|---|---|---|
| Fast fixture on mixed metals, plastics and rubber | surface-insensitive ethyl grade | below 5 s on steel, aluminum, ABS, PVC and nitrile (LOCTITE 401, Henkel TDS February 2012) |
| PP and PE without a primer | CA/epoxy hybrid | lap shear 0.5 N/mm² (72 psi) on PE, 0.6 N/mm² (87 psi) on PP (LOCTITE HY 4090, Henkel TDS July 2019) |
| PP with a primer | ethyl grade plus aliphatic-amine primer | block shear 15 N/mm² (2,200 psi), LOCTITE SF 770 with LOCTITE 406 (Henkel TDS May 2021) |
| Gaps up to 5 mm (0.2 in) | two-part CA gel | open time 90 to 180 s (LOCTITE 3090, Henkel TDS September 2012) |
| Higher service temperature | by cyanoacrylate type; check the grade data sheet | 85 to 250 °C (185 to 480 °F) across types (Permabond producer article, 2016) |
| Peel, impact, water or polar solvents | epoxy or structural acrylic instead of cyanoacrylate | cyanoacrylate is brittle, with poor water and polar-solvent resistance (Permabond producer article, 2016) |
| Topical skin closure devices (US) | n-butyl or 2-octyl medical grades | 21 CFR 878.4010 Class II (special controls) |
Each request is passed straight to independent companies of that trade, and no company pays AdhesiveAdditives.com to be named or to receive requests; the editorial policy explains how.
Limits of Cyanoacrylate Adhesives#
Cyanoacrylate adhesives have six limits, from blooming to bottle gelation, and the six are listed below.
- Blooming or frosting next to the bond line.
- Brittle failure under impact or peel.
- Poor resistance to water and polar solvents, with hydrolytic degradation.
- Limited gap fill outside two-part gels.
- Slow cure on acidic or dry surfaces.
- Bottle gelation when moisture enters the container.
What a cyanoacrylate should not be used on follows from the list: unprimed PE, PP, PTFE and TPE, joints loaded in peel or impact, and wet service. Permabond names brittleness, poor water and polar-solvent resistance and limited gap fill as the limits of the class (producer article, 2016). For gaps, peel and water the alternative is an epoxy, and the epoxy vs cyanoacrylate trade-off in gap fill, strength, speed and substrates is set out under epoxy vs cyanoacrylate.
Cyanoacrylate Adhesive Grade Types Compared#
Cyanoacrylate adhesives come as general-purpose and surface-insensitive ethyl grades, rubber-toughened grades, methyl grades for metal, n-butyl and 2-octyl medical grades, and two-part CA gels and CA/epoxy hybrids for gaps and polyolefins.
The table sets each cyanoacrylate grade type against its monomer or system, one dated grade value and its use.
| Type | Monomer or system | Dated grade evidence | Use |
|---|---|---|---|
| General-purpose, plastics and rubber | ethyl 2-cyanoacrylate | LOCTITE 406: 12 to 22 mPa·s; 15.5 N/mm² lap shear after 24 h (Henkel TDS February 2012) | plastic and rubber parts |
| Surface-insensitive | ethyl 2-cyanoacrylate | LOCTITE 401: 70 to 110 mPa·s; fixture below 5 s on steel, aluminum, ABS, PVC, nitrile (Henkel TDS February 2012) | mixed and porous substrates |
| Rubber-toughened | ethyl 2-cyanoacrylate | LOCTITE 480 (Henkel TDS July 2024); grade description only | joints with a brittleness risk |
| Metal bonding | methyl 2-cyanoacrylate | strong bonds to metals (Permabond producer article, 2016) | metal parts |
| Medical | n-butyl and 2-octyl cyanoacrylate | 21 CFR 878.4010 classes; US20130095262A2 Example 1 is a 2-octyl composition | skin closure devices |
| Device assembly | ethyl 2-cyanoacrylate | LOCTITE 4011: fixture ABS 1 to 2 s, steel 20 to 45 s; tested to Henkel protocols based on ISO 10993 (Henkel TDS December 2020) | catheters, needles, tubing sets |
| Two-part | CA gel; CA/epoxy hybrid | LOCTITE 3090: gap up to 5 mm; LOCTITE HY 4090: fixture below 180 s, Tg 88 °C | gaps; PE and PP without primer |
Every value in the table is a typical product value of the named grade on its dated data sheet, not a class value, and a second producer's grade of the same type carries its own numbers. Since all seven types share one monomer family, the type label tells a buyer which data sheet fields to compare rather than which value to expect. The rubber-toughened row names its grade without values, and the medical row cites a device rule instead of a grade, because medical cyanoacrylates are classified as devices.
Cyanoacrylate Adhesives in Industry#
Industrial cyanoacrylate use spans electronics, small-part assembly and medical devices, each served by its own grade type.
Among the types of adhesives by chemistry, cyanoacrylates are the anionic member of the chemically curing group, placed next to epoxy, polyurethane and acrylic in the overview of types of adhesives by chemistry.
Where Are Industrial Cyanoacrylate Adhesives Used?#
Industrial cyanoacrylate adhesives are used in electronics assembly, rubber and plastic small-part assembly and medical device assembly. The three uses are listed below.
- Electronics adhesives: wire and coil tacking on printed circuit boards, cured with an activator applied after the adhesive.
- Small-part assembly: nitrile and neoprene rubber, ABS and PVC parts that fixture in seconds.
- Medical device assembly: ethyl grades tested to producer protocols based on ISO 10993.
In electronics the activator is a separate product, such as LOCTITE SF 7452, applied after the adhesive.
Medical Cyanoacrylate Adhesives: n-Butyl and 2-Octyl Grades#
Medical cyanoacrylate adhesives use n-butyl and 2-octyl esters, and 21 CFR 878.4010 classifies tissue adhesives for topical skin approximation as Class II (special controls) and non-topical tissue adhesives as Class III (premarket approval). The classification dates from 73 FR 31033 of 2008-05-30 and covers devices, not adhesive raw materials.
Device assembly is the second medical use: LOCTITE 4011 fixtures ABS in 1 to 2 seconds and steel in 20 to 45 seconds and is tested to Henkel protocols based on ISO 10993 (typical product values, Henkel TDS December 2020). Catheters, needles and tubing sets are the assembled parts, and medical device adhesives as a group are covered under medical device adhesives.
Responsibility splits in two. The formulator supplies biocompatibility data on the cured adhesive, and the device maker owns the biological evaluation of the finished device.
What Should a Cyanoacrylate Adhesive Data Sheet State?#
A cyanoacrylate adhesive data sheet should state each value as a typical product value with its temperature, humidity, substrate and method. Without those conditions a fixture time or a viscosity cannot be compared, because fixture moves with humidity and gap and viscosity moves with shear rate.
Comparing adhesive manufacturers and suppliers works only on identical fields, and how to qualify and source them is covered under adhesive manufacturers and suppliers. The six fields below make two cyanoacrylate data sheets comparable.
- Monomer type: ethyl, methyl, n-butyl, 2-octyl or a hybrid system.
- Viscosity with shear rate and temperature, such as cone and plate at 3,000 s⁻¹ and 25 °C.
- Fixture time per substrate at a stated relative humidity.
- Strength with its test method and cure time.
- Service temperature range.
- Storage temperature and shelf life.