Freudenberg develops ETU-free chloroprene rubber compounds

Weinheim, Germany – Freudenberg Sealing Technologies has developed new chloroprene rubber compounds that require no ethylene thiourea (ETU) accelerator.

The new elastomer has been created through developing a new vulcanisation method that will not require ETU, said FST in a statement 10 July.

ETU is used as an accelerator in the vulcanisation of chloroprene rubber to provide low-temperature flexibility as well as resistance to media such as greases and lubricants.

The substance, however, poses the risk of reproductive toxicity and is damaging on fruit, according to FST.

And so far “there have been no alternatives that offer a similar performance or even meet the requirements,” the company added.

According to FST, the newly developed compound now meets the strict requirements of the automotive industry without the use of ETU.

The Weinheim-based seals maker said it is already supplying sealing bellows made with the elastomer for joint seals in tie rods, control arms and wishbones in the automotive industry.

Those components protect the moving parts from external influences and the leakage of lubricants.

FST said it considered a range of factors while developing the compound, including the optimisation of mixing processes as well as the material’s fulfilment of automotive requirements.

Furthermore, it used thermal analyses such as differential scanning calorimetry to determine key parameters such as the melting and crystallisation temperature, relaxation, glass transition temperature and degree of vulcanization.

The measurements have shown that one of the most important requirements, i.e. behaviour in the low temperature range, is being met “extremely well”, FST added.

“This is also confirmed by feedback from customers in the automotive sector that are already using ETU-free sealing bellows,” said the company statement.

After artificial aging in water and relevant greases, other parameters such as tensile strength and elongation at break were also “within the requirement specifications”.

This was verified after the corresponding preconditioning with seven days at 70 °C (158 °F) in grease, 10 days at 80 °C (176 °F) in water and 48 hours in 70 °C (158 °F) hot air.