Summary

As the EU restrictions on D4, D5, and D6 enter a new phase of application, buyers should not focus simply on whether a silicone raw material “contains siloxanes.” They need to determine whether the commercial product is a silicone polymer or a mixture, whether the cyclic siloxanes are intentionally added or present as process residues, and which concentration condition applies to the actual use.

The News in Brief

Commission Regulation (EU) 2024/1328 amended Entry 70 of Annex XVII to REACH, expanding the restrictions on the following three cyclic volatile methyl siloxanes:

• Octamethylcyclotetrasiloxane, D4, CAS 556-67-2;
• Decamethylcyclopentasiloxane, D5, CAS 541-02-6;
• Dodecamethylcyclohexasiloxane, D6, CAS 540-97-6.

The general placing-on-the-market restriction entered its applicable phase after June 6, 2026. Under the general rule, D4, D5, or D6 may not be placed on the EU market as a substance on its own, as a constituent of another substance, or in a mixture when the concentration of the respective substance is equal to or greater than 0.1% by weight.

However, 0.1% is not the only criterion that can be directly applied to all silicone oils, silicone elastomers, and organosilicon mixtures. The regulation also distinguishes silicone polymers on their own, specified industrial uses, mixtures containing cyclic siloxanes as residues from silicone polymers, and products with deferred application dates.

The first step in procurement verification is therefore not to require every raw material to reach a “non-detect” level immediately. Buyers should first confirm the product form, how D4, D5, and D6 are present, and the final use.

Which Raw Materials Should Be Rechecked First?

Silicone Oils Without Individual D4, D5, and D6 Data

Silicone oils are commonly purchased according to viscosity, appearance, refractive index, volatile matter, and functional group content. These indicators can describe processing performance and application characteristics, but they cannot directly demonstrate whether D4, D5, and D6 individually meet the applicable requirements.

A common procurement mistake is to interpret “low volatile matter” as “low cyclic siloxane content.”

Total volatile matter may include water, solvents, low-molecular-weight linear siloxanes, and other volatile components. Even if the total volatile matter result is low, it cannot replace separate quantitative results for D4, D5, and D6.

For silicone oils intended for the EU market, buyers should confirm whether the supplier reports:

• Individual test results for D4, D5, and D6;
• The combined amount of the three substances;
• Total volatile matter;
• Or low-molecular-weight siloxanes without clear differentiation.

Only the first type of result can be used directly to determine the concentration of each restricted substance.

Silicone Elastomer Gels Containing Carrier Fluids

Silicone elastomer gels generally consist of a crosslinked silicone polymer network and a carrier fluid. Even if the cyclic siloxane residue in the crosslinked polymer itself is low, the carrier phase in the complete commercial product may change the final D4, D5, and D6 levels.

A test report stating only “silicone elastomer tested” is therefore insufficient. Buyers need to confirm whether the sample refers to:

• The dry crosslinked elastomer;
• The polymer base before the carrier is added;
• The carrier fluid;
• Or the complete commercial gel or dispersion.

If the supplier provides data only for the dry polymer while the purchased product is a carrier-containing gel, the conclusion in the report cannot directly represent the delivered product.

Silicone Mixtures Used in Adhesives, Sealants, and Coatings

D4, D5, and D6 in some adhesives, sealants, casting materials, coatings, and moulding materials may be process residues from silicone polymers rather than intentionally added solvents or functional components.

These products cannot be assessed solely on the basis of the words “industrial use.” Buyers need to confirm all of the following:

1. Whether the product is a mixture containing a silicone polymer;
2. Whether the cyclic siloxanes are present only as polymer residues;
3. Whether the actual use falls within a specified application under the regulation;
4. Whether that use is subject to a separate residual concentration condition.

The table below provides selected examples of use-related assessments and does not represent a complete list of regulatory derogations.

The actual assessment should be based on the commercial form in which the product is placed on the market, the final use, and the full provisions of Entry 70 of Annex XVII to REACH. A conclusion should not be made solely from the selected examples in the table.

What Will Not Change Immediately?

Silicone Oils and Elastomers Will Not Be Prohibited as Entire Material Classes

The restrictions apply to D4, D5, and D6 under specified conditions, not to every polysiloxane material.

Buyers do not need to replace an established formulation immediately simply because the raw material is based on silicone chemistry. A more appropriate approach is to verify:

• Whether the raw material is a silicone polymer on its own or a mixture containing a silicone polymer;
• Whether D4, D5, and D6 are intentionally added or present as residues;
• Whether the general 0.1% condition or a use-specific condition applies;
• The actual concentrations in the final product.

A change of grade or reformulation should be considered only when the existing raw material cannot provide sufficient evidence, shows excessive residue variation, or prevents the final product from meeting the applicable conditions.

Performance Parameters Still Determine Whether a Material Can Be Used

Lower D4, D5, and D6 residue levels do not mean that a raw material can directly replace the existing silicone oil or elastomer.

The viscosity, volatility profile, molecular weight distribution, and functional group content of silicone oils may affect spreading, lubrication, defoaming, film formation, and processing stability. The degree of crosslinking, carrier type, gel strength, and dispersion state of silicone elastomer gels may affect sensory properties, rheology, compatibility, and storage stability.

Regulatory data address market access and residue assessment. They cannot replace application validation.

Four Types of Information Commonly Misinterpreted in Procurement Documents

“REACH Compliant” Does Not Mean That D4, D5, and D6 Have Been Fully Verified

A general REACH declaration can only indicate that the supplier claims to have assessed the relevant requirements. It does not demonstrate:

• Which version or restriction entry was assessed;
• Which product form was used as the basis of the assessment;
• Whether the actual downstream use was considered;
• Whether batch-specific test data are available;
• Whether each of the three substances is below the applicable value.

A more useful declaration should identify the product name, commercial form, intended use, and the relevant provision of Entry 70 used for the assessment.

“D4/D5/D6 Free” Requires a Clear Analytical Basis

The terms “free,” “zero,” and “not contained” may be understood to mean complete absence, but in practice they may indicate:

• Not intentionally added;
• Below the method detection limit;
• Below the limit of quantification;
• Below an internal specification;
• Or a theoretical assessment based only on the formulation.

Buyers should ask the supplier to explain the precise meaning of the claim and avoid interpreting “not intentionally added” as “analytically not detected.”

Total Volatile Matter Cannot Replace Individual Cyclic Siloxane Results

Total volatile matter can be used to assess the overall volatile components in a silicone oil or elastomer, but the regulatory restrictions apply to the respective concentrations of D4, D5, and D6.

A COA that reports only total volatile matter without individual results therefore cannot independently support an assessment of D4, D5, and D6 compliance.

A One-Time Test Report Does Not Demonstrate Long-Term Batch Control

A compliant sample result shows only that the tested sample met the relevant specification at the time of testing.

D4, D5, and D6 residues may be affected by polymerisation conditions, stripping, vacuum devolatilisation, residence time, carrier fluids, and changes in the manufacturing site. After sample validation, bulk purchasing still requires confirmation of the supplier’s control approach:

• Testing every batch and reporting the results on the COA;
• Periodic monitoring at a defined frequency;
• Control through process parameters and internal release specifications;
• Or reliance only on historical representative data.

The higher the raw-material risk, the greater the dosage, and the closer the final product is to the applicable limit, the more clearly batch-data requirements should be defined.

What Questions Should a Test Report Answer?

REACH Entry 70 does not specify one universal test method for all silicone oils and silicone elastomers. During quality verification, buyers may ask suppliers to provide a validated gas chromatographic method suitable for the material matrix, such as GC-FID or GC-MS, and explain the method’s suitability.

At a minimum, the test report should answer the following questions:

For complex elastomer gels, buyers should also confirm whether the sample-preparation procedure covers both the polymer network and the carrier phase, and whether the reported result is a direct measurement or a calculated value based on component data.

Sample Validation and Bulk Procurement Involve Different Risks

During the sample stage, attention is often focused on a single test result and application performance. Bulk procurement, however, is more likely to expose process variation and inconsistencies in documentation.

Sample Stage

R&D personnel generally focus on:

• Viscosity, dispersibility, and formulation compatibility;
• The sensory or rheological properties of an elastomer gel;
• Curing, film formation, or processing behaviour;
• Whether the initial D4, D5, and D6 results meet the target specification.

A successful sample does not mean that the bulk-production grade has been fixed. A supplier may provide a laboratory sample that has undergone additional devolatilisation, while the standard production grade is controlled under different conditions.

Bulk Procurement Stage

Quality and procurement personnel need to confirm:

• Whether the sample and bulk product use the same product code;
• Whether they come from the same manufacturing site and process route;
• Whether D4, D5, and D6 are included in the formal release specification;
• Whether the COA contains actual batch results or fixed declaration values;
• Whether changes in the process, carrier, or test method trigger advance notification.

If the supplier cannot explain the relationship between the sample and the bulk product, even a strong sample-test result should not be used as the sole basis for approving long-term procurement.

What Should R&D, Quality, and Procurement Evaluate Separately?

Verification of D4, D5, and D6 cannot be handled by one department alone because different roles need to answer different questions.

A more reliable internal process is for R&D to determine whether the material can be used, quality to determine whether the data can be trusted, procurement to confirm bulk-supply conditions, and regulatory personnel to determine whether the data apply to the target market and final use.

Short-Term and Mid-Term Implications

What Information Should Buyers Provide to Suppliers?

To obtain quotations and documentation that can support an actual assessment, buyers should avoid stating only that a material “must comply with EU D4, D5, and D6 requirements.”

More useful information includes:

• Raw-material type and target viscosity, form, or carrier requirements;
• Final use, such as silicone oil, elastomer gel, sealant, or coating;
• Whether the product will be placed on the EU market;
• Internal D4, D5, and D6 specifications;
• Whether individual batch COA results are required;
• Requirements for the test method, limit of quantification, and reporting units;
• Sample quantity, bulk requirement, and estimated annual volume;
• Whether a supplier regulatory declaration and change-notification commitment are required.

For silicone elastomer gels, buyers should also state that the complete commercial product needs to be assessed rather than only the dry polymer.

Conclusion

As the EU restrictions on D4, D5, and D6 enter a new phase, the core issue in purchasing silicone oils and elastomers is not to reduce every organosilicon material to a “non-detect” level. It is to establish a verifiable assessment chain:

Commercial product form—how cyclic siloxanes are present—final use—applicable concentration condition—analytical evidence—bulk control.

If any part of this chain is unclear, a general REACH declaration, low volatile-matter data, or a one-time sample report may be misinterpreted.

When contacting ChemicalCell about organosilicon materials, buyers can submit an RFQ with the intended use, product form, D4/D5/D6 specifications, quantity, target market, documentation requirements, and sample needs so that the available grade and relevant technical documentation can be reviewed further.