Choosing nitrosamine-safe accelerators

Where do nitrosamines come from?

Some accelerators release a secondary amine during vulcanization. This amine reacts with nitrogen oxides in the air or in the compound and forms an N-nitrosamine.

Whether the resulting nitrosamine is harmful depends on the structure of the amine. Nitrosamines formed from dimethylamine, diethylamine, dibutylamine and morpholine are considered carcinogenic. Those formed from dibenzylamine and diisobutylamine are not on this list.

Why does it matter?

Germany's workplace rule (TRGS 552) and EU regulations on baby bottle teats and toy balloons set nitrosamine limits. Automotive and consumer product manufacturers exporting to Europe therefore ask for nitrosamine-safe accelerators in their supply chain.

For companies producing in Turkey and selling to Europe, this is a requirement that directly affects the choice of compound formulation.

Substitution table

The substituted and substituting materials have different molecular weights. For an equivalent effect the dosage is usually increased and the compound formulation is readjusted with a rheometer.

Points to watch in the transition

Nitrosamine-safe materials usually have a higher molecular weight and some are slightly slower. Scorch time, cure time and modulus must be measured in the new compound formulation.

Changing only the accelerator may not be enough: other amine sources in the compound (some antidegradants, processing aids) should also be reviewed.