Since 24 August 2023, EU REACH has required professional and industrial users of products containing more than 0.1% total monomeric diisocyanates to complete training before use, renewed at least every five years. The US has no equivalent training rule, but workplace exposure limits apply and EPA has proposed a 0.1% threshold for TDI in consumer products. Polyurethane adhesive and sealant makers can respond in three ways: keep the formula and support customer training, bring free monomer below 0.1%, or move to a different chemistry such as silane-modified polymers. Each route changes something different, and the hardest part of all three is finding every product the decision touches.
What REACH entry 74 requires
The restriction is entry 74 of REACH Annex XVII, adopted in August 2020 under Commission Regulation (EU) 2020/1149. According to guidance from Ireland's Health and Safety Authority:
- It applies to products with total monomeric diisocyanate content above 0.1% by weight.
- Labels must carry the statement "As from 24th August 2023, adequate training is required before industrial or professional use of this product."
- Users must complete training before use, renewed every five years, and employers keep the records.
- Suppliers must make sure training is available to the customers they sell to.
The rule restricts use without training. It does not ban polyurethane adhesives. That leaves room for a business decision, and the decision belongs to R&D as much as to regulatory.
What applies in the US
The US has no federal equivalent of the EU training requirement. The rules that apply to polyurethane adhesives and sealants are workplace exposure limits and a proposed consumer-product rule:
- Workplace limits: for MDI, OSHA's permissible exposure limit is a ceiling of 0.02 ppm. Cal/OSHA in California sets a tighter 8-hour average of 0.005 ppm, the same as NIOSH's recommended limit and the ACGIH threshold limit value.
- Consumer products: in January 2015, EPA proposed a Significant New Use Rule under TSCA for TDI and related compounds in consumer coatings, adhesives, elastomers, binders and sealants above 0.1%. Companies would have to notify EPA at least 90 days before starting or resuming such a use. EPA's page still lists the rule as proposed, with no final rule.
- Enforcement focus: OSHA ran a National Emphasis Program on isocyanates from 2013. That directive is now archived and no longer represents OSHA policy.
For a company selling on both sides of the Atlantic, 0.1% is the number that matters in both markets. It triggers EU training, and it is the level EPA proposed for consumer TDI products. That makes below 0.1% a sensible single design target, though US customers still have to meet their own workplace exposure limits when they apply the product.
Three routes, and what each one changes
- Keep the formula and support training. What changes: the label, the SDS and customer communication. What the team has to prove: that every affected product carries the statement and that training is offered to each customer.
- Reduce free monomer below 0.1%. What changes: prepolymer chemistry and process, often viscosity and reactivity. What the team has to prove: monomer content on every batch, plus unchanged cure, open time and bond performance.
- Switch to silane-modified polymers or another isocyanate-free system. What changes: the cure mechanism, adhesion profile, mechanical properties and moisture sensitivity in the package. What the team has to prove: full requalification against each customer specification.
Low-monomer prepolymers keep the polyurethane backbone, but removing free monomer usually raises viscosity and can change how fast the product cures. Silane-modified polymers cure with moisture through silane groups instead of isocyanate groups. They often bond well without primers on many substrates, but they need drying agents to keep shelf life, and they don't match every polyurethane on strength or temperature resistance. Non-isocyanate polyurethanes made from cyclic carbonates and amines are still mostly at development scale.
None of these is a drop-in swap. Each one starts a new set of formulation trials, and the results have to stay connected to the product they will replace, the same discipline that adhesive scale-up depends on.
Where-used sets the size of the workload
The real size of a diisocyanate program depends on how many products and customer approvals sit downstream of each isocyanate-bearing raw material. A worked example: a sealant maker has 40 finished products above the 0.1% threshold. Each is approved by an average of three customers. If the company reformulates, that is 120 requalification conversations, each with its own test plan, before any sales are protected.
The count is rarely that clean. Many companies make their own prepolymers and use one intermediate in several finished products. A diisocyanate that never appears on a finished product's ingredient list can still be there through the prepolymer. Material rationalization runs into the same problem, as in four sealants doing one job: dependencies stay out of sight until something forces a change.
A test you can run this week
Pick one isocyanate-bearing raw material, such as an MDI-based prepolymer component. Then:
- List every finished product that contains it, directly or through an intermediate.
- Find the calculated or measured free-monomer content for each.
- Mark which are above 0.1% and which customers approve each one.
- For the products you might reformulate, find the most recent qualification data you would be repeating.
If step 1 needs a week of spreadsheet work and conversations with long-serving formulators, the reformulation plan is being built on a partial list.
What this means for polyurethane adhesive and sealant makers
- Do you know every product above 0.1% monomeric diisocyanate, including through in-house prepolymers?
- Which products are worth reformulating, and which are better kept with training support?
- For a silane-modified alternative, which customer specifications would it fail on today?
- When the next restriction arrives on a different substance, could you answer the same questions faster?
Seeing every affected formula before reformulation starts
Uncountable's Regulatory Management checks recipe and ingredient data against jurisdictional limits held in a maintained regulations database, so a threshold like 0.1% can be screened during development rather than after launch. Product Lifecycle Management adds where-used views across intermediates and finished products, and reformulation trials stay connected to the products they are meant to replace. Teams still make the regulatory call, with the evidence for it on the recipe.
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