Food Contact Rubbers 2: Products, Migration and Regulation, Volume 16, Number 2, 2006

Chapter 5: Improving the Safety of Rubber as a Food Contact Material

5.1 Nitrosamines

Nitrosamines form as a result of the reaction of nitrosating agents (e.g., nitrogen oxides in the ambient atmosphere) with secondary amines in the rubber. One of the most prolific sources of secondary amines is a number of the accelerators that are used in sulfur based cure systems; the amines being breakdown products produced as a result of the chemical reactions taking place during vulcanisation. Specific examples of these accelerators, their secondary amine products, and the nitrosamines derived from them are given in Table 40.

Table 40: Nitrosamines derived from some commonly used sulphur accelerators

Accelerator

Secondary Amine

Nitrosamine

TMTD, TMTM and ZDMC

Dimethylamine

N-nitrosodimethylamine

TETD and ZDEC

Diethylamine

N-nitrosodimethylamine

MBS

Morpholine

N-nitrosomorpholine

ZDBC

Dibutylamine

N-nitrosodibutylamine

DPTD

Piperidine

N-nitrosopiperidine

With atmospheric nitrogen being one of the most important nitrosating agents, nitrosamines are easily formed in rubber compounds during both the mixing of the compound and the subsequent fabrication steps (e.g., extrusion and moulding) and they can also be formed during analytical work. A significant amount of work has been carried out by Rapra (136) on the influence of mixing procedures, vulcanisation temperatures, extraction procedures and analysis techniques and the results obtained have shown that a wide variation in nitrosamine levels can be detected in essentially identical compounds.

The main approaches that have been taken to ensure that the amount of nitrosamine (and nitrosatable compounds) in a given compound is as low as...