Mixing

For mixing EPDM, the internal mixer is most suitable due to the high loading levels. The batch size is critical for optimization of the mixing cycle. The recommended fill factor is slightly larger than for most rubbers, but may vary depending on the degree of loading and the hardness of the compound.

An upside-down cycle is recommended as the standard technique. Here the carbon black and oil are added first, followed by the polymer. Single stage mixing is usual.

The oil-extended BUNA EP grades are best suited for mill mixing because band formation occurs immediately. Here, too, EPDM grades with higher molecular weight and those with higher ethylene content easily accept large quantities of fillers and are therefore easy to handle.

 

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