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Sumitomo Chemical has developed a new type of rubber material that remains flexible and elastic even in temperatures as cold as -40 degrees C.

The material is composed of ethylene-propylene-diene rubber (EPDM) and boasts of high cold resistance.

According to Sumitomo’s engineers, the new rubber material it keeps an elasticity and flexibility equivalent to those at normal temperatures, enabling continued performances of parts. This makes them best suited for radiator hoses, weatherstrips and sealing materials.

The new EPDM features an improved molecular structure. This was achieved with Sumitomo Chemical increasing the randomness of the positions of ethylene (E) and propylene (P). For example, their new layout can be “-P-E-P-E-E-P-E-P-E-P-E-.”

Because E and P are almost alternately placed, it is not easily crystallized, contends the engineers.

On the other hand, conventional EPDMs have a layout of, for example, “-P-E-E-E-E-P-P-P-P-E-E-.” Because E (or P) is concentrated, when the temperature of that portion becomes low, it is easily crystallized.

The compression set at a temperature of -40°C (an index of elasticity or low-temperature rubber elasticity) of the new EPDM is 60% while that of conventional EPDMs is 75-85%. This index becomes zero when rubber completely comes back to its original shape after being compressed.

And this further becomes 100% if rubber does not retain its original shape at all. This implies that the lower the value, the higher the material’s elasticity becomes.

On the other hand, the glass transition temperature (an index of (low-temperature) flexibility) of the new EPDM is -60°, which is 10-15°C lower than that of conventional EPDMs (-50 to -45°C). It means that the flexibility of the new EPDM does not lower much even at low temperatures.

Content: Nikkei Technology. Image credits: REUTERS/Regis Duvignau/Files

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