Sealing lips

What are sealing lips?

Sealing lips are thin-walled, elastic elements on the outer edge of a seal that are in direct contact with the surface to be sealed. They form the functional part of many sealing systems, such as rotary shaft seals, piston seals, rod seals and Bellows. Their task is to ensure a permanent and controlled seal between two components, even if relative movements or pressure fluctuations occur.

The sealing lip acts on the mating surface via a defined contact pressure. This results from the elasticity of the material and often an integrated spring (e.g. in the case of Shaft seals). As a result, the contact remains constant even in the event of wear or slight shaft misalignment.

Typical construction forms:

Simple sealing lip: a sealing edge for standard applications
Double lip: additional dust lip to protect against dirt or external particles, while at the same time forming a lubricant reserve
Multiple lips: combined sealing for different media or pressure ranges

The geometry and preload of the sealing lip significantly determine the sealing effect, friction and service life of the entire system.

Functions & applications of sealing lips

The sealing lip plays a central role in the function of sealing systems. It ensures that the space to be sealed remains sealed by moulding itself elastically to the shaft or housing surface. The right balance of compressive force, lubrication and elasticity creates a reliable seal while minimising wear.

Typical functions:

Sealing of liquids and gases with rotating or linear movements
Prevents the ingress of dust, dirt and moisture
Reduction of friction and leakage losses
Protection of neighbouring components against corrosion and wear

Areas of application:

Automotive industry: Radical shaft seals on crankshafts, gearboxes and drive shafts
Hydraulics and pneumatics: rod and piston seals with optimised lip profiles
Mechanical engineering: Sealing of bearings, pumps and Gearbox housings
Medical technology and food industry: hygienic silicone sealing lips for clean media routing
Building services: Sealing of fittings, Valves and rotating sealing points

Materials & variants of sealing lips

Sealing lips are usually made from elastomer materials that have a high restoring force, temperature and media resistance. For special applications, thermoplastic or PTFE-coated materials are also used to reduce friction or increase chemical resistance.

Typical materials:

NBR (acrylonitrile butadiene rubber): widely used, oil and grease resistant, good elasticity
FKM (fluororubber, e.g. Viton®): high temperature and chemical resistance, ideal for engine and transmission systems
EPDMSuitable for water, steam and outdoor applications, resistant to ozone and weathering
Silicone (VMQ): excellent recovery behaviour over a wide temperature range (-60 °C to +200 °C)

With Metal-rubber combinations the sealing lip is mounted directly onto a carrier ring vulcanised, in order to achieve a permanent material bond

Depending on the application, the geometry of the sealing lip is optimised with reinforcing ribs, lubricating grooves or micro-structured surfaces in order to adapt the contact pressure, lubricating film formation and wear behaviour. The result is a highly functional component that seals permanently even under extreme operating conditions.

Further entries

Stainless steel

Stainless steel is a corrosion and temperature-resistant material that is used for durable, hygienic and mechanically resilient components in demanding technical applications.

Rubber-Plastic Composite Parts

Rubber-plastic composite parts are hybrid components in which elastic and thermoplastic components are functionally combined - ideal for seals, housings and flexible technical solutions.

Shaft seal

A shaft seal is a sealing element that seals between a rotating shaft and a housing. It prevents lubricants from escaping and at the same time protects against dirt, dust and moisture.

SBR: styrene-butadiene rubber

SBR is a cost-effective, abrasion-resistant elastomer with good mechanical properties that is mainly used in tyres, seals and general moulded rubber parts.

IRHD hardness (International Rubber Hardness Degree / ball indentation hardness)

IRHD hardness is an internationally standardised method for measuring rubber hardness using ball pressure and is particularly suitable for small or sensitive elastomer components.

Sealed seats

Sealing seats are machined contact surfaces that accommodate seals in a form-fit and force-fit manner, thus ensuring permanent media separation protection.

EPDM: Ethylene propylene diene rubber

EPDM is a weather, UV and chemical-resistant elastomer with high thermal stability that is used in particular for durable seals, hoses and outdoor applications in industry and construction.

Sulphur crosslinking

Sulphur crosslinking is a proven vulcanisation process in which rubber is crosslinked with the aid of sulphur to form an elastic, dimensionally stable and mechanically resilient material.

Rubber-fabric composite parts

Rubber-fabric composite parts are elastic components with integrated fabric inserts that ensure high tensile strength, dimensional stability and dynamic load-bearing capacity - for example in membranes, seals or conveyor belts.

Fatigue

Fatigue refers to the progressive degradation of material due to repeated mechanical stress and is a key factor in the design of durable technical components.

Polymerisation

Polymerisation is the chemical reaction in which many monomers are combined to form long polymer chains - the basis for plastics and rubber elastomers.

Express Services

Express production refers to the particularly fast production of prototypes, tools or small batches and accelerated development projects with drastically reduced delivery times.

Metal oxide crosslinking

Metal oxide crosslinking is a crosslinking process that is mainly used for chloroprene rubber and produces particularly durable, ageing and flame-resistant rubber parts.

Protective housing

A protective housing encapsulates sensitive components and prevents damage caused by dirt, water or impact.

Pressure resistance

Pressure resistance is the resistance of a material to compressive stress and is a decisive factor for the function and service life of technical components under mechanical stress.

Adhesion

Adhesion is the physical holding force between two different materials at their interface and is a key factor for strong, durable connections in technology and industry.

Stress cracking

Stress cracking is the gradual formation of cracks in plastics due to the interaction of stress and chemical media - often with critical consequences for component safety.

Heat resistance

Heat-resistant materials retain their properties at high temperatures and are ideal for industrial and technical applications.

Tempering

Annealing is a thermal post-treatment that reduces residual stresses, stabilises material properties and improves the functionality of technical components.

Burr formation

Burr formation occurs in primary forming processes due to material escaping from mould parting surfaces and joints during forming and requires targeted reworking to ensure component quality.

PC: Polycarbonate

Polycarbonate (PC) is a transparent, impact-resistant plastic that is used for high-quality housings, visible parts and functional composite components.

FVMQ: Fluorosilicone

FVMQ is a cold-flexible, fuel- and weather-resistant fluorosilicone elastomer that is primarily used in the aviation and automotive industries for demanding sealing applications.

Rubber blank

A rubber blank is a non-crosslinked, mouldable elastomer precursor that is processed in moulding tools to produce elastic rubber parts.

HTV silicone: High-temperature curing solid silicone

HTV silicone is a high-temperature curing solid silicone rubber that becomes a permanently elastic material when heated. It combines high mechanical strength with excellent resistance to temperature, ageing and chemicals.

Toolmaking

In elastomer production, toolmaking refers to the development and manufacture of high-precision tools that are used in the production of rubber, plastic and composite parts for moulding.

Elongation at break

The elongation at break indicates how much a material can stretch under tensile load before it tears.

LABS (paint wetting impairment substances)

LABS are substances that interfere with the wetting of paints and must therefore be strictly avoided or tested in paint-critical applications.

Freeze deburring

Freeze deburring is a process for removing burrs, particularly on rubber parts, by cooling and mechanical blasting.

Caoutchouc vs. rubber vs. elastomer

Rubber is the raw material, rubber is the end product created by vulcanisation, and elastomer is the superordinate material class of elastic polymers.

Seals

Seals prevent leaks in pipework, motor and system components. They also compensate for manufacturing tolerances and protect processes against pressure, temperature and media stress.

Rubber recycling

Rubber recycling includes mechanical, thermal and chemical processes for the reuse of vulcanised rubber products as raw materials or additives in new applications.

Grommets

Grommets are ring- or disc-shaped protective inserts that are inserted into openings or edges to allow cables to pass through safely. Grommets protect cables and hoses from sharp edges, seal feed-throughs and can be quickly inserted into holes or gaps.

brass

Brass is an easily machinable, corrosion-resistant copper-zinc alloy that is widely used as a functional and decorative metal - including in rubber-metal composite parts, fittings and electrical components.

Profile seal

A profile seal is a seal with a defined cross-sectional shape (round, rectangular, hollow or with a complex profile) that ensures a seal between two components. It is made from elastomers and is used wherever gaps, movements or unevenness need to be compensated for.

GRP: Glass fibre reinforced plastic

GRP (glass fibre reinforced plastic) is a robust, lightweight composite material made from glass fibres and a plastic matrix that is used in a wide range of applications in industry, construction and mobility.

Polyurethane (PU)

Polyurethane (PU) is a robust, abrasion-resistant plastic with high elasticity and chemical resistance, which is primarily used in heavily loaded technical components, dampers and composite solutions.

Saturated and unsaturated polymers

Saturated polymers have only single bonds in the main chain and are resistant to ageing, while unsaturated polymers contain double bonds in the main chain and are easier to crosslink; EPDM is a speciality because its double bond is in the side chain.

Titanium

Titanium is an extremely corrosion-resistant, lightweight and high-strength material that is used in aviation, medical technology and for rubber-metal composite parts in aggressive environments.

Rubber buffers

Rubber buffers are elastic elements that absorb and dampen shocks, oscillations and vibrations. They protect machines, devices and assemblies from mechanical loads, compensate for movements and reduce noise in technical applications.

IIR: Butyl rubber

Butyl rubber (IIR) is a particularly gas-tight, weather- and chemical-resistant elastomer that is mainly used in tyres, seals and membranes.

Compression moulding

Compression moulding is a process for manufacturing moulded rubber parts in which a rubber compound is compressed under pressure and heat in a closed mould and vulcanised directly.

Prototype construction

Prototyping is the targeted production of functional sample parts for early testing and optimisation of geometry, material behaviour and processability before the start of series production.

Rapid tooling

Rapid tooling is the accelerated production of functional tools for the rapid production of prototypes or small series under near-series conditions.

Vacuum cups

Suction cups are suction cups made of elastomer or plastic that cling elastically to the surface and trap the resulting vacuum. Suction cups create an adhesive connection between the gripper and the workpiece by means of negative pressure.

HNBR: Hydrogenated NBR

HNBR is a particularly heat-, oil- and ageing-resistant elastomer that is ideal for durable seals and technical components in dynamically stressed applications.

Fillers

Fillers are functional additives in rubber or plastic compounds that specifically influence mechanical properties, processability or cost structure.

Rubber expansion joints

Rubber expansion joints are flexible connecting elements that compensate for movements, vibrations and pressure surges in pipework. Thanks to their elastic structure, they can absorb changes in length, lateral displacements and angular movements and thus protect connected system components from mechanical stress, vibrations and tension in the pipework system.

Assembly Services

Component assembly comprises the assembly of individual components into a functional unit as an assembly.

NR: Natural rubber

Natural rubber (NR) is a highly elastic, tear-resistant elastomer made from renewable raw materials that is primarily used in dynamically stressed components such as tyres, dampers and conveyor belts.

Mould cavity / cavity

Mould cavities are the cavities in a mould that give the component its final geometry during the moulding process.

Valves

Valves control, throttle or shut off liquids and gases in pipework, motors and hydraulic systems. They are crucial for process reliability and efficiency.

Abrasion

Abrasion is the mechanically induced surface wear of a material caused by friction and has a decisive influence on the service life and usability of technical components.

Ageing

Ageing describes the gradual change in material properties due to external influences such as heat, UV radiation or media, which can lead to long-term impairment of function and service life.

Outgassing

Outgassing is the escape of volatile substances from materials and can lead to malfunctions, contamination or optical faults in sensitive applications.

Injection moulding

Injection moulding is a precise moulding process for manufacturing complex plastic and rubber parts in which the material is injected into a mould under pressure and cured there.

ISO 9001

ISO 9001 is the world's most important standard for quality management. It defines how companies manage their processes so that products and services deliver consistently high quality and fulfil customer requirements.

LSR: Liquid silicone

LSR is a liquid silicone rubber produced on a VMQ or FVMQ basis and processed by injection moulding. The material combines high elasticity, purity and temperature resistance.

CFRP: Carbon fibre reinforced plastic

CFRP (carbon fibre reinforced plastic) is an ultra-light, extremely strong composite material made of carbon fibres and a plastic matrix that is used in highly stressed lightweight construction applications.

FDA conformity

FDA compliance means that a material or product meets the requirements of the U.S. Food and Drug Administration and is safe for contact with food, drinking water or pharmaceutical applications. Only approved ingredients may be used and the material must not release any substances of concern into the medium.

Vibratory finishing (barrel finishing)

Mass finishing or barrel finishing is a mechanical mass finishing process in which surfaces are machined and burrs removed using abrasive media and movement.

Rubber caps

Rubber caps reliably protect components from dust, moisture and mechanical impact.

RTV silicone: Room temperature curing solid silicone

RTV silicone is a room temperature curing silicone rubber that cures without heat or pressure. It is particularly suitable for sealing, bonding, potting and mould making and is less strong and temperature-resistant than HTV and LSR.

FKM: Fluororubber

FKM is a heat- and chemical-resistant high-performance elastomer for seals and components in extremely demanding industrial applications.

Silane crosslinking

Silane crosslinking is a moisture-controlled crosslinking process for plastics and elastomers that enables mechanical stability at moderate processing temperatures.

ISO 13485

ISO 13485 explained: an overview of the requirements, areas of application and benefits of certification for medical technology.

Tool costs

Tool costs are the expenses for the manufacture of tools and have a significant influence on the profitability of series production.

Transfer moulding

Transfer moulding is a rubber moulding process in which the material is pressed from a heated chamber into a closed mould where it is cross-linked under pressure and temperature - ideal for precise components with inserts.

Medical device regulation (MDR)

The Medical Device Regulation (MDR) is the central EU regulation for medical devices, which places high demands on safety, documentation and market surveillance.

Elasticity

Elasticity is the ability of a material to deform under load and then return completely to its original shape - essential for flexible technical components.

PPA: Polyphthalamide

Polyphthalamide (PPA) is a dimensionally stable, chemical and temperature-resistant high-performance plastic that is used in particular for precise, media-resistant components and rubber-plastic composite solutions.

PES: Polyester

Polyester (PES) is a robust, chemical-resistant thermoplastic that is used both as an engineering plastic and as a fabric reinforcement in rubber composite parts.

PPS: Polyphenylene sulphide

Polyphenylene sulphide (PPS) is a high-temperature and chemical-resistant precision plastic that is used in media-exposed and dimensionally critical components, especially in hybrid solutions.

Crosslinking chemicals

Cross-linking chemicals ensure the permanent elasticity and dimensional stability of rubber through chemical reaction - a key component in the production of functional rubber parts.

Vibration dampers

Vibration dampers reduce vibrations and noise in machines and vehicles.

Rebound resilience

Rebound resilience describes the ability of a material to return energy after rapid deformation - crucial for dynamic applications such as spring elements or dampers.

Bellows

A bellows is an elastic component with a corrugated, accordion-like geometry that absorbs movements, changes in length or swivelling movements without losing its protective or sealing function. It protects sensitive components such as joints, shafts or guides from dirt and moisture and at the same time enables a flexible, permanently movable connection.

Biocompatibility

The proof of biocompatibility proves through standardised tests that a medical device or material does not cause any harmful reactions in the human body.

CR: Chloroprene rubber

Chloroprene rubber (CR) is a versatile, weather- and flame-resistant elastomer that is often used for seals, hoses and technical components for indoor and outdoor use and is also known as neoprene.

Adhesion promoter

Adhesion promoters are chemical bonding agents that permanently bond rubber with other materials and thus form the basis for resilient rubber composite parts.

Valve seal

A valve seal is an elastic component that reliably seals the flow of gases or liquids in a valve. The seal prevents leaks, compensates for pressure and temperature changes and ensures that the valve fulfils its switching, control or shut-off function reliably and permanently.

Molded Rubber Parts

Moulded rubber parts are elastic components made from vulcanised rubber by pressing, transfer moulding or injection moulding. They are manufactured according to drawings and are used as sealing, damping or functional elements in technical applications.

Glass transition temperature

The glass transition temperature (Tg) is the temperature range in which a polymer changes from elastic to glassy and largely determines its low-temperature flexibility.

Sealing lips

Sealing lips are flexible sealing elements that securely enclose media and remain reliably functional even in the event of rotation or pressure fluctuations.

Elastomer rollers

Rubber rollers transmit forces, dampen vibrations and protect surfaces in printing machines, conveyor systems and packaging lines.

NBR: Acrylonitrile butadiene rubber

Acrylonitrile butadiene rubber (NBR) is an oil and fuel-resistant elastomer that is frequently used for seals, hoses and technical moulded parts in mechanical engineering and vehicle construction.

Anti-ageing agent

Anti-ageing agents are functional additives that protect elastomers and plastics from damaging influences such as oxygen, ozone, UV radiation or heat, thereby significantly extending their service life.

Compound

A compound is a customised material mixture of polymer and additives that is specifically tailored to the requirements of a particular technical application.

Synthetic rubber

Synthetic rubber is an industrially manufactured elastomer material that is categorised into main chemical groups and whose properties can be specifically adapted to technical requirements.

Copolymerisation

Copolymerisation is the simultaneous polymerisation of different monomers to produce polymers with specifically adjustable properties for technical and industrial applications.

CAD modelling

CAD modelling is the digital design of technical components and tools that serves as the basis for production, simulation and prototype development in industry.

PP: Polypropylene

Polypropylene (PP) is a lightweight, chemical-resistant thermoplastic with a wide range of applications that is ideal for technical plastic parts and rubber-plastic composite solutions.

Degreasing

Degreasing is an essential cleaning step for removing residues from components to ensure optimum adhesion during vulcanisation, bonding or coating.

Azo and urea compounds

Azo and urea compounds are speciality chemicals that are used as blowing or cross-linking agents in rubber processing - especially for foams and friction-active components.

DIN ISO 3302-1

DIN ISO 3302-1 defines the general tolerances for moulded rubber parts and is an international standard for ensuring dimensional accuracy in elastomer processing.

Oil resistance

Oil-resistant materials permanently withstand aggressive oils and are used in seals, hoses and technical components.

Sampling

In engineering, sampling is the testing and approval of sample parts of a new or revised product or manufacturing process.

EN 9100

EN 9100 explained: an overview of the requirements, areas of application and benefits of certification for the aviation, aerospace and defence industries.

PU: Polyurethane elastomer

PU elastomers are dimensionally stable, abrasion-resistant plastics with high mechanical strength that are ideal for rollers, seals and shock absorbers in heavy-duty industrial applications.

Series production

Series production refers to the repeated, economical manufacture of similar components in large quantities.

Tool cleaning

Tool cleaning ensures reliable, clean moulding, protects against burr formation and extends the service life of tools in series production.

TPE: Thermoplastic elastomers

TPEs are elastic, malleable materials with rubber-like behaviour that can be thermally processed and recycled like plastics - ideal for flexible seals, handles and hybrid parts.

Rubber-Metal Composite Parts

Rubber-metal composite parts are mechanically stable components in which elastomer and metal are inseparably combined - ideal for bearings, dampers and technical sealing systems.

Keyboard and switch covers

Keyboard and switch covers are elastic protective components that protect keys and operating elements from dust, moisture and dirt. At the same time, they maintain the operating function by transmitting the actuation feel and enabling reliable sealing.

PA: Polyamide

Polyamide (PA) is a robust, wear-resistant plastic with very good strength and chemical resistance, which is used in particular in technical components and rubber-plastic composite systems.

Vulcanisation

Vulcanisation is the process in which raw rubber is converted into a permanently elastic, dimensionally stable and durable rubber state through chemical cross-linking.

Special alloys

Speciality alloys are highly developed metal mixtures for extreme requirements in technology, medicine and industry - especially where corrosion, temperature or load limits of standard materials are exceeded.

Cold resistance

Cold resistance describes the ability of a material to remain functional and elastic at low temperatures - crucial for seals and elastomer components in outdoor or cold applications.

Deburring

Deburring is the process of removing burrs from components to ensure the function, appearance and safety of technical products.

Plasticiser

Plasticisers are additives that make rubber and plastics more elastic and easier to process and are mainly used in flexible sealing and moulded parts.

Tensile strength

The tensile strength is the maximum stress that a material can withstand under tensile load and is a key parameter for the mechanical strength of elastomers.

VMQ: Silicone rubber

Silicone rubber (VMQ) is a heat-, cold- and UV-resistant elastomer with very good insulation and media resistance, which is frequently used in medical, food and automotive technology.

Engine damper

Engine dampers are elastic elements that absorb vibrations and shocks between the engine and the vehicle or machine frame. They reduce vibrations, protect adjacent components from stress and improve the noise and running behaviour of the entire system.

Bearing bolt

A bearing pin is a cylindrical connecting element that serves as a pivot or swivel axis for moving components. It transmits forces, guides movements and secures the position of components within a bearing or a joint connection.

Extrusion of rubber

Rubber extrusion is a continuous manufacturing process for rubber-elastic profiles, hoses and seals in which the material is pressed through a moulding die and then vulcanised.

Aluminium

Aluminium is a lightweight, corrosion-resistant material with high thermal conductivity that is used in a variety of ways as a construction material and support element in technical components.

Cycle time

The cycle time describes the complete duration of a production run during injection moulding or pressing and is a key parameter for efficiency and output.

Suction pad

Suction cups are cup-shaped suction cups made of elastomer or plastic that cling elastically to the surface and trap the resulting vacuum. Suction cups create an adhesive connection between the gripper and the workpiece by means of negative pressure.

Autoclaves

An autoclave is a heatable pressure vessel for the thermal treatment of materials - e.g. for the post-vulcanisation of elastomers or for sterilisation in medicine and technology.

Residual materials

Residual materials are recyclable material residues from production that can be specifically collected and fed back into the production cycle to conserve resources.

Peroxide crosslinking

Peroxides are reactive cross-linking chemicals that produce stable, temperature- and chemical-resistant elastomer structures without sulphur bridges in rubber processing.

Elongation

Elongation refers to the change in length of a material under tensile load and is a key parameter for assessing the elasticity and breaking strength of technical materials.

Primer

Primers are adhesion-promoting primers that improve the adhesion between rubber, plastic or metal and ensure a permanent bond in composite and coating applications.

Rubber

Rubber is an elastic material of natural or synthetic origin that is vulcanised into durable components for sealing, damping and technical applications.

Housing and cover with integrated seal

Housings and covers with integrated seals are components in which the sealing function is embedded directly in the plastic or metal part. The sealing function is usually realised as an overmoulded or pressed-in rubber sealing lip. They enable reliable sealing without a separate sealing component and are often used for compact, easy-to-install assemblies.

Shore hardness

The Shore hardness measures how deeply a test pin penetrates a material and thus provides information about its degree of hardness - a decisive factor in the selection of elastic and technical materials.

RoHS

RoHS restricts the use of certain hazardous substances in electrical and electronic equipment in order to reduce environmental and health risks. Products may only be sold in the EU if all components comply with the specified limits for listed hazardous substances.

REACH

REACH is an EU regulation for the registration, evaluation and regulation of chemical substances in order to better protect people and the environment. Companies must prove the safety of the raw materials they use and inform customers if their products contain substances of concern.