RoHS

Definition and Scope

RoHS stands for Restriction of Hazardous Substances and refers in the EU context primarily to Directive 2011/65/EU. It is EU product law and defines which hazardous substances may only be contained in limited amounts in certain products on the EU market. As a result, it acts directly on material selection, specification, and verification along the supply chain.

What is regulated are electrical and electronic equipment (EEE) — that is, devices that need electric currents or electromagnetic fields for their function. For sealing technology, what is decisive is that RoHS does not only consider the complete device. It also captures components, materials, and surfaces within the EEE. A seal, an O-ring, a molded seal, or a seal profile therefore falls under RoHS as soon as it is a part of EEE — for example in a sensor, an actuator, or an electrically actuated valve.

In practice, this means: anyone designing, sourcing, or approving seals for EEE has to clarify early where the part is later used, which EEE category it is assigned to, and which material layers (e.g., coatings) are present. This classification determines whether and how RoHS verification has to be carried out.

Restricted Substances and Limit Values (per Homogeneous Material)

RoHS restricts ten substances or substance groups. The limit values apply per “homogeneous material” (definition see below). For most substances, the limit lies at 0.1 mass-% (1000 ppm). For cadmium, 0.01 mass-% (100 ppm) applies. The four phthalates have been restricted in many EEE categories since July 22, 2019, and are therefore particularly relevant for polymer-based materials.

What Does “Homogeneous Material” Mean in Sealing Technology?

A homogeneous material is a material that cannot be further mechanically separated into different materials — for example by unscrewing, grinding, peeling, or separating layers. This definition is central for seals, because limit values are not applied to the overall part “on average”, but to each material level individually.

With a seal, this frequently means a split into several test units. The seal body made of elastomer is typically a homogeneous material. A coating, a release agent, a surface treatment, or an adhesive, by contrast, is usually considered its own homogeneous material when it is present as a layer and is mechanically separable. Precisely here, errors frequently arise, because drawings or BOMs state “a seal”, while the component consists of several RoHS-relevant material layers.

Phthalates as Plasticizers: Relevance for Elastomers and Plastics

Phthalates are plasticizers — that is, additives that can make polymers softer and more flexible. RoHS does not assess the material name but the concentration in the specific compound (recipe). A blanket statement such as “EPDM is RoHS-compliant” is therefore too coarse technically, because what is decisive is the recipe, the supplier, and possibly the layer system.

For seals, not only plasticizers are relevant. Pigments, stabilizers, or flame retardants can also be sources of RoHS substances. In practice, this leads to the question of which recipe is used, whether a material change has taken place, and how changes are documented. Particularly with colored compounds or coated seals, targeted material testing pays off when the supply chain does not deliver reliable data.

Verification and Technical Documentation (Practice in the Supply Chain)

RoHS conformity is usually secured via technical documents. A widespread framework for this is IEC 63000:2016, which describes how information and evidence for the assessment of RoHS substance restrictions can be structured and collected. For seals as components, this usually runs via document-based supply chain evidence, supplemented by testing when risk is elevated.

Customary verification building blocks are:

• Material declarations (ingredients/material structure, often at recipe or material level)
• Supplier declarations on RoHS conformity
• Test reports from laboratories, when documents are not sufficient or when a suspicion exists

Analytically, a stepwise approach is frequently used. XRF (X-ray fluorescence) typically suits as a screening for many elements (e.g., Pb, Cd), but it does not provide a direct statement for phthalates. Phthalates are therefore mostly determined via chemical analysis (e.g., chromatographic methods). In practice, this selection is often risk-based: material class, supplier history, coloring, coatings, and application area determine how deeply testing has to go.

Distinction from REACH and Typical Pitfalls with Seals in EEE

RoHS and REACH are frequently named together in everyday practice but have different roles. RoHS is product law for EEE and sets substance limit values in the device and its components. REACH is chemicals law with its own scope, restrictions, and information obligations. Both regulatory frameworks can be relevant in parallel — for example when a substance is both restricted under RoHS and regulated under REACH.

In sealing technology, RoHS topics frequently arise where seals sit in electrically relevant assemblies — for example in sensors, actuators, electrically actuated valves, controls, valve manifolds, or cable feedthroughs. The component acts mechanically but is part of EEE and is therefore in scope under RoHS.

Typical pitfalls recur in many projects:

• The EEE reference is recognized too late, because the part is considered a “mechanical seal”.
• Several homogeneous materials are overlooked — for example coating or adhesive on the seal body.
• Additives in the compound are underestimated, although the recipe determines the actual RoHS relevance.
• Changes in the supply chain (new compound, new masterbatch, different coating) are not cleanly re-documented, although they can change the substance balance.

When the classification takes place early and material levels are cleanly separated, RoHS can usually be handled without major effort. With complex layer systems or unclear recipes, specialized consultation or targeted analysis is often sensible.