Deutsch English

Sponge rubber - the material

Sponge rubber differs from cellular rubber in that it is has a mixed open and closed cell structure. This rubber material has a high compression elasticity and good resilience. It is available as natural or synthetic rubber in forms such as chloroprene, EPDM, silicone, Buna or fluorine rubber. The raw materials used bond particularly well with the special material structure of sponge rubber. At first glance sponge rubber appears to have the same appearance as cellular rubber. Closer inspection will reveal the difference. Inside, sponge rubber has a mixed open and closed cell structure.

It differs from cellular rubber also in that it requires the addition of an outer skin if it is to be used for sealing applications.

Sponge rubber enlarged view
Sponge rubber enlarged view
Sponge rubber sheet
Sponge rubber sheet


KÖPP sponge rubber profile and round cord have a high compression elasticity combined with particularly good resilience. Under light pressure the profile flexes out to the surrounding surfaces making a perfect seal.


Sponge rubber profiles are available with various degrees of softness. Soft profiles are used in applications involving light closing pressures while hard profiles are more suited to heavy closing pressures. The softness of sponge rubber is varied by using special mixes and by varying its volume by weight, i.e. its density.


All KÖPP sponge rubber profiles have a thick outer skin. Inside they have the fine porous structure characteristic of sponge rubber. There are two methods for manufacturing sponge rubber profile: moulding and extrusion.

Technical data

  • Excellent sealing properties (with skin)
  •  High compressibility
  • Good insulation properties
  • Easy to work
  • EPDM - mixture with high temperature and ageing resistance 
  • CR/NBR - mixture with high flame retardance rating and high resistance to oils
sponge rubber
sponge rubber

Mixture types

NR – Natural rubber
high elasticity, good stability under cold conditions.

CR – Chloroprene rubber
high flame retardance, good ozone, weather, chemical and ageing resistance

SBR – Styrol butadiene rubber
good mechanical properties, good heat resistance and ageing stability

NBR – acrylNitrile Butadiene Rubber
good resistance to petrol, mineral oils and greases

EPDM – Ethylene Propylene Diene Rubber
high ageing stability, high resistance to ozone, good resistance to heat and chemicals

FPM – Fluorine rubber
very high heat and chemical resistance, high flame retardance, high ageing stability, highly weatherproof

Processing methods

Round cord, square and moulded sponge rubber profiles are vulcanised in heated metal moulds. During the vulcanising process chemical cross-linking takes place and it is this feature which gives sponge rubber is rubbery elastic characteristics. Adding foaming agents creates the cell structure and the final shape of foam rubber. The final shape depends of course on the production mould.

Extruded profiles, on the other hand are not shaped in a closed mould. They are formed by extrusion, that is by forcing a special rubber mixture through a nozzle or die which has the final shape of the finished profile. Vulcanising takes place outside the die at room temperature.
KÖPP sponge rubber profile is available in standard lengths or as ready made parts custom-made to your shape and version requirements.

moulded profile
moulded profiles
moulded parts
moulded parts

Sponge rubber round cord, square profile and moulded profile are available in self-adhesive versions ideal for making a clean, durable seal around circular and square openings.
This is a tried-and-tested, cost-effective solution for sealing large openings in containers, tanks and casings. To make fitting easier, we supply versions which are self-adhesive on one side or both sides.

Sponge rubber sheets are ideal for custom cut-outs or punched items.

Take advantage of our experience and expertise. We will be glad to advise you about the sponge rubber that matches your application. KÖPP sponge rubber – durable, dependable, cost-effective.

Go here to find out about other applications for our products.
Find out more about other applications for our product »