Technical information

Rubber design considerations

Design considerations

Designing rubber parts involves different considerations about the type of rubber, the grade, tolerances required, etcetera. With our knowledge of manufacturing processes, you can expect highly uniform consistency within a production lot, and from lot-to-lot. To take full advantage of these characteristics, a few simple guidelines should be considered for the continued long term mechanical effectiveness of your final assembly.

Material selection

  • environmental strengths, limitations
  • static or dynamic sealing
  • chemical resistance
  • temperature resistance
  • etc…

Attachment

  • groove fit
  • adhesive
  • hardware mounting
  • compression fit
  • etc…

Cross section profile

Gap sealing – min/max compression, depending on material selected:

  • sponges, foam, hollow shapes @ 10%-30%
  • dense solid shapes @ 2%-30%

Shape – factor to address when determining the cross section:

  • exterior perimeter
  • interior solid or hollow

Compression force / closing force

  • durometer low or high (see below)
  • solid vs. sponge or foam
  • hollow interior to lessen force
  • static or dynamic pressure
  • sponges have low closure force, dense shapes have higher sealing capability

New types of solid rubber have made the difference between solid and sponge rubber very small. We can offer solid rubber parts in hardnesses of 10° IRHD. This hardness is comparable to sponge rubber!! A 2K solid – sponge rubber combined extrusion is also available.

Compression set

  • allowable percentage of height relaxation
  • recovery rate from compressed state to relaxed height

Other considerations

  • abrasion resistance
  • color matching
  • secondary finishing – holes, notches, die-cutting, etc

We can help you make the right decisions with our technical know how and experience.

Rubber grade

Selecting the best elastomer for an application involves answering many questions. Temperature and other environmental factors can affect the long-term physical properties of a compound. The best place to begin a search is with existing information. Look for a material with a solid balance of the properties desired for the application. For new products, similar applications can provide valuable information.

Standard rubber grades

Our standard compounds cover a vaste range of applications as shown below.

Name
ASTM
Trade names
Properties vulcanized rubber / polymer
Natural rubber
NR
Crepe
General purpose rubber with balanced physical properties. Non-ageing and weathering resistant only with suitable stabilization.
Isoprene rubber
IR
Natsyn
Like NR
Butadiene rubber
BR
Buna CB
General purpose rubber almost exclusively used in cuttings. High elasticity, drive stability and cold flexibility.
Butadiene/styrene rubber
SBR
Buna SB
Frequently used general purpose rubber. Non-aging and weathering resistant only with suitable stabilization.
Chloroprene
CR
Neoprene
Rubber with a relatively high resistance to flames, weather and aging. Medium resistance to oil and fuel.
Nitrile rubber
NBR
Buna N
High swelling resistance to oil, fat and fuel. Degrees of resistance, elasticity and cold flexibility depend on the acrylonitrile content.
Hydrogenated nitrile rubber
HNBR
Therban
Hydrogenated HNBR with higher resistance to ozone and aging.
EPDM rubber
EPDM
Buna AP / Keltan
High resistance to aging
Butyl rubber
IIR
Exxon butyl
High air- tightness, good damping properties and heat resistance. There are also special halogenated types (BIIR, CIIR).
Chlorohydrine rubber
CO / ECO
Hydrin
High resistance to oil, fat, fuel, heat and oxygen.
Chlorosulfonated polyethylene
CSM
Hypalon
Similar to EPDM yet better swelling resistance to oil, fat and fuel. High resistance to chemicals and flames
Acrylate rubber
ACM
Hytemp
Excellent resistance to oil, fat and fuel especially to hypoid oil. Low cold flexibility. oil,
Fluoro rubber
FPM / FKM
Viton / Fluorel
Excellent resistance to chemicals and heat.
Silicone rubber
VMQ
Likonsil
High resistance to aging
Fluorosilicone Rubber
FVMQ
Likonsil F
High resistance to aging, weather and heat. Extremely high cold resistance. High resistance to oil and fuel.
Perfluoro Rubber
FFKM
Kalrez
Highest resistance to chemicals and heat.
Thermoplastic elastomers
TPE / TPV / TPR
SBS / SEBS

Special rubber grades

Special compounds can be formulated when standard qualities do not fulfill specific requirements. Such requirements may also relate to: a) mechanical properties such as compression set, creep or stress decay b) chemical properties c) sanitary, safety requirements or the use in extreme conditions

Examples

  • antimicrobial rubber
  • fire retardant grades
  • extreme low temperature grades that are flexible down to -100° C
  • antistatic and ESD rubber

Durometer

The hardness of rubber or rubber-like materials is measured in durometer by penetration of an indentor into the sample. The ability to modify base polymers by compounding, the addition of other materials, enables mixes to be produced from each in a wide range of hadnesses. The value most suitable for a product often needs to be determined by a practical trial or rig test. Hardness is one of many properties that define the material required for a particular application. (Shore hardness is often used as a proxy for flexibility (flexural modulus). This is an empirical, not a fundamental relationship).

Comparison of rubber and rubber like materials

Durometer

Technical assistance

When in doubt, we are here to help with the formulation of compound requirements and design issues. If you have any questions, please feel free to contact us.

LIKON

Mail address

P.O. Box 23
Zeeland, 5410 AA
The Netherlands

Visiting address

Kerkstraat 101
Zeeland, 5411 CK
The Netherlands

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