Technical reference

Adhesive Solvent Systems

The solvent leaves the bond entirely, and decides how the product ships, which markets it can enter and how much assembly time you get. Which is more than the polymer decides about buying it.

Last updated: 2026-09-15

The part that evaporates decides the most

The polymer decides what the bond can do. The solvent decides whether you can buy it, ship it and run it. None of it ends up in the joint, and all of it ends up on your dangerous-goods paperwork, your VOC declaration and your line speed.

Which is why "can you make it toluene-free" is one of the most common questions we get, and why the honest answer involves a trial rather than a yes.

What the solvent decides

Decides	How
Dangerous goods class	Through flash point. Below 23°C makes the product UN 1133, Class 3 — which changes shipping, warehousing and insurance together.
Market access	Through VOC content. The solvent is most of what the VOC figure measures, so it decides which markets the product can legally enter.
Open time	Through evaporation rate. A faster solvent gives a shorter window and a quicker line; a slower one gives more assembly time and more chance of trapped solvent.
Workplace exposure	Through toxicity and odour. This is what usually drives a customer request for a specific substitution, rather than regulation.
Substrate compatibility	Through solvency. Aggressive solvents dissolve polystyrene and attack PU foam, so a strong solvent system rules out whole substrate families.

The solvents, and where we stand on each

Stated plainly, including the ones we will not use. A supplier who lists no restrictions has not thought about the question.

Toluene

Available, and increasingly refused

Traditional workhorse in contact and shoe adhesive — strong solvency, moderate evaporation, low cost.

The most common substitution request we receive. Driven by workplace exposure limits and customer policy more often than by an outright legal ban. Toluene-free formulations are made on request — and what replaces toluene matters as much as removing it, so check section 3 of the SDS for the grade you are quoted.

Xylene

Available, often substituted alongside toluene

Slower evaporating aromatic, used where a longer open time is wanted.

Requests to remove toluene usually mean xylene as well — worth stating explicitly rather than assuming.

Acetone

Available

Fast evaporating ketone. VOC-exempt under US EPA 40 CFR 51.100(s).

The main route to a lower US VOC number without going water-based. But it is more flammable than the toluene it replaces, so the dangerous-goods position can get worse while the VOC number improves.

Ethyl acetate

Available

Moderate evaporation, milder odour than aromatics, good solvency for many rubbers.

Often the practical compromise in a toluene-free contact adhesive — closer to the original behaviour than acetone.

MEK (methyl ethyl ketone)

Available

Fast ketone with strong solvency; also used as a surface cleaner before bonding.

Restricted in some jurisdictions and increasingly scrutinised. Check the destination before designing a formulation around it.

Hexane

Restricted

Aliphatic solvent, historically common in rubber cements.

Restricted or prohibited in a number of markets on neurotoxicity grounds, and in many brand restricted-substance lists. Trade-named aliphatic blends such as "No. 6 solvent oil" can be largely hexane, so ask for CAS numbers rather than the trade name.

Methylene chloride

Restricted

Very strong solvency, non-flammable.

Carcinogenicity concerns and tightening restriction in the US and EU, and one of the halogenated hydrocarbons China’s indoor-adhesive standard limits separately. It sometimes replaces aromatics in adhesives sold as benzene-free, so a "no benzene" label says nothing about whether it is present. Our water-based grade is specified at zero methylene chloride.

Mixed aromatics ("mixed benzene")

Not benzene-free

Industrial blends of benzene-series aromatic solvents, sold under trade names such as mixed benzene or aromatic solvent naphtha.

These blends are the same family as the "three benzenes" — benzene, toluene and xylene — whatever the product label says. A product made with them cannot honestly be described as benzene-free; the measured content is what a test report can speak to.

Benzene

Prohibited

A known human carcinogen, prohibited as an adhesive solvent. If a supplier’s SDS shows it, that is the end of the conversation.

Substituting a solvent is a process change

The polymer is untouched, so bond strength, heat resistance and durability stay where they were. What moves is everything to do with running it:

Stays the same	Changes
Peel and shear strength	Open time and flash-off — the biggest practical effect
Heat resistance	Viscosity, and therefore gun and nozzle settings
Chemical resistance	Odour, and how the operator judges readiness
Durability and ageing	VOC figure and dangerous-goods position
Substrate range, usually	Foam and polystyrene compatibility, sometimes decisively

Which is why a substitution needs a line trial, not a datasheet comparison.An operator who has judged tack by smell and feel for ten years will get it wrong on the first shift with a new solvent system, and that shows up as a bond failure attributed to the adhesive.

"Benzene-free", "formaldehyde-free" and "eco": reading the claim

Solvent-borne SBS and polychloroprene contact adhesives are widely sold as "eco", "environmentally friendly" or free of benzene and formaldehyde. Some of those claims hold up and some do not, and the difference is usually visible in documents the supplier already has.

The "three benzenes"

Benzene, toluene and xylene — often grouped as BTX, or 三苯 in Chinese trade usage — are the aromatic solvents contact adhesives were traditionally built on. All three are liquids at room temperature. Industrial "mixed benzene" and aromatic solvent naphthas are blends from the same family, so an adhesive made with them is not free of the three benzenes, whatever it is called.

Where formaldehyde comes from

Solvents are not the only source. Polychloroprene contact adhesives commonly use alkylphenol-formaldehyde tackifying resins, such as p-tert-butylphenol formaldehyde resin, which are made from formaldehyde. Most of it is bound into the resin, but some free formaldehyde can remain, and that is what a test measures. An adhesive built on these resins can have low free formaldehyde; it cannot sensibly be called formaldehyde-free without a measured result.

Four statements that are not the same

Statement	What it actually means	Ask for
Not intentionally added	A formulation declaration. Nothing has been measured, and impurities in raw materials are not covered.	A signed declaration for the named grade
Not detected	Below the detection limit of a specific test method — which may or may not be low enough for your requirement.	The method, the detection limit, the laboratory and the date
Within the limit	A measured value at or below a standard's limit. It can be well above zero and still pass.	The measured values, not only the word "pass"
Zero	Not a test result. It is one of the three statements above, restated as marketing.	Which of the three it really is

What replaces the aromatics

—n-Hexane and hexane-rich aliphatic blends — restricted in many markets and brand policies on neurotoxicity grounds.
—Chlorinated solvents such as methylene chloride — non-flammable and strong, but halogenated hydrocarbons carry their own limits and restrictions.
—Ester, ketone and cycloaliphatic blends — ethyl acetate, acetone, cyclohexane and similar — usually the better route, with their own flammability and open-time trade-offs set out in the table above.

What China's indoor-adhesive standard checks

GB 18583, the Chinese standard for harmful substances in adhesives used in interior decoration, sets separate limits for solvent-based adhesives on free formaldehyde, benzene, toluene plus xylene, halogenated hydrocarbons such as methylene chloride, and total volatile organic content; GB 33372-2020 sets VOC content limits by carrier, adhesive type and application field together. Meeting either means the measured values sit under the limits — not that the substances are absent. See our VOC limits by market for how the VOC figures compare between countries.

Five checks before accepting an eco claim

Read SDS section 3. Mixed aromatics, methylene chloride or n-hexane listed there cannot sit beside a benzene-free or eco label.
Compare the language versions. The Chinese and English SDS should list the same components with the same CAS numbers; a mistranslated component is a document error you will inherit at customs.
Check the hazard statements. A product classified as a suspected carcinogen, a skin sensitiser or a marine pollutant is difficult to describe as environmentally friendly, whatever else is true of it.
Ask for the test report on the exact grade. It should name the standard, give each result with its detection limit, and state the laboratory and date.
Make sure it matches what ships. A report on a sample from years ago, or on a sibling grade, does not cover the drums in your container.

Where the requirement is genuinely to remove organic solvent rather than to relabel it, compare water-based options by application.

Replacing solvent with water is the largest substitution of all: drying, equipment, freezing risk and heat resistance all change, and the polymer often changes too. See water-based adhesive options by application for what to recheck.

How to specify a solvent system

1.Name the exclusions, not the preference. "Toluene and xylene free" is actionable. "Low odour" is not.
2.Say where it comes from. A legal limit, a customer policy and an internal preference lead to different answers about how far to go.
3.State the open time you need. This is the constraint the substitution has to preserve, and the one most often left out of the brief.
4.Say whether foam or polystyrene is involved. It rules out whole solvent families before anything else is discussed.
5.Ask for the SDS of the result. Section 3 with CAS numbers is the only authoritative statement of what is actually in the tin.

If the driver is a VOC limit rather than a specific substance, thelow-VOC manufacturing routesare the better starting point — solvent substitution is only one of four.

Frequently asked questions

Why do buyers ask for toluene-free adhesive?

Usually workplace exposure rather than an outright ban. Toluene has tight occupational exposure limits, and many manufacturers — particularly those supplying European or American brands — carry a customer policy that excludes it regardless of local law. There is also a REACH dimension for EU importers. The performance question is separate: a well-designed toluene-free system using ethyl acetate or a ketone blend performs close to the original, though evaporation behaviour and therefore open time will shift, so it needs re-trialling on your line rather than dropping in.

Does changing the solvent change how the adhesive performs?

It does not change the polymer, so bond strength, heat resistance and durability stay broadly where they were — those are set by the base polymer. What does change is process behaviour: evaporation rate moves open time and flash-off, viscosity shifts, and odour and drying feel different to the operator. In practice a solvent substitution is a process change more than a performance change, and it should be trialled at line speed before it goes into production.

What is a VOC-exempt solvent and does it make the adhesive safer?

Certain solvents — acetone, methyl acetate, PCBTF and others — are excluded from the VOC calculation under US EPA 40 CFR 51.100(s) because they contribute negligibly to ozone formation. Using them can bring a solvent-borne adhesive under a US limit without going water-based. It is not a safety claim: acetone is exempt and more flammable than toluene, so the dangerous-goods classification can worsen while the VOC figure improves. And the exemption is US federal: China's GB 33372-2020 deducts only acetone, methyl acetate and dimethyl carbonate for solvent-based adhesives.

Which solvents will attack polystyrene or PU foam?

Strong ketones and aromatics — acetone, MEK, toluene — dissolve expanded and extruded polystyrene and can collapse the cell structure of polyurethane foam. This is why a general-purpose contact adhesive is the wrong product for bonding insulation board or upholstery foam, and why foam work needs a foam-safe grade with a milder solvent system or a water-based carrier. Always trial on the actual foam: densities and grades differ in how much they tolerate.

Can you supply an adhesive with a specific solvent excluded?

Usually yes, and it is one of the more common formulation adjustments we make. Tell us which substances your specification or customer policy excludes — toluene and xylene together is the most frequent request — along with the substrate pair and your line speed, because the substitution has to preserve the open time your process needs. What we will not do is claim a substitution is performance-neutral without trialling it.

Is a "benzene-free" or "eco" solvent-based contact adhesive automatically safer?

No. Removing benzene, toluene and xylene only matters if what replaces them is better, and common replacements include n-hexane and chlorinated solvents such as methylene chloride, which are restricted in their own right. Formaldehyde is a separate question: polychloroprene adhesives often use alkylphenol-formaldehyde tackifying resins, so a "formaldehyde-free" claim needs a measured free-formaldehyde result, not a label. Read section 3 of the SDS for every solvent and its CAS number, check the hazard statements match the claim, and ask for a test report on the exact grade that gives each result with its detection limit.

How do I know what solvent is actually in an adhesive?

The safety data sheet. Section 3 lists the hazardous components with their CAS numbers, which is the authoritative answer regardless of what the technical data sheet or the marketing says. If a supplier will not send an SDS for the exact grade quoted, treat that as the answer to a different and more important question.

Around the solvent question

What the base polymer actually decides
Chloroprene, SBS, PU, water-based and silicone — heat, flex and durability are set the moment the family is chosen.
When the driver is a VOC limit, not a substance
Solvent substitution is one of four routes — and not always the right one.
Removing the solvent entirely
No flash point, no dangerous goods, at a cost in dry time and heat resistance.
How to read the numbers on a datasheet
What each figure predicts, what it does not, and why one without its test method is not comparable.
Look up a term and its other names
Non-acid silicone is neutral cure; liquid nails is grab adhesive. Fifty terms with their synonyms.
Storage, shelf life and what heat does to it
Why a container crossing the tropics at 60-70°C is the hardest storage condition your adhesive will see.
Check the VOC limit for your destination market
Which instrument actually governs adhesives in the US, EU and China — and which ones are wrongly cited.
Eight checks before you pick a supplier
Manufacturer or trader, grade-level test data, VOC position and dangerous-goods handling — apply them to us too.
Browse the full technical library
Every reference page and guide, grouped by the question it answers rather than by date.
Send a specification and get a quote
Substrate, volume and destination market are enough for us to price it.

Tell us what your specification excludes

Name the substances, the open time you need and whether foam is involved. That is enough for us to say whether a substitution is straightforward, needs a trial, or is better solved by changing carrier entirely.

Send a technical enquiry See the four low-VOC routes