Technical information
Rubber design considerationsDesign 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
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.