Smell of nitrile

[berti]

Hi experts,

today I am looking for help.

VDA (German car producers association) has a test method for the smell of rubber parts used in the passenger compartments of cars. Method is basically: ready cured part is put to a closed container (glass or metal), the container is heated e.g. for 1 hour to 80 °C, then cooled down, opened and sniffed by test persons giving a subjective evaluation from 1 ( no smell) to 6 ("stinky&quot.

For technical reasons the part has to be made from nitrile (NBR) and cured by a kind of sulfur system. Unfortunately all tests up to now came out with "6".

- Which types of NBR would be best (kind of emulgator etc.)?

- Other additives (plasticizer) ?

- Most important: Which sulfur cure system ? Type of accelerators ? Level of sulfur ?

Your help is very much appreciated.

Berti

 

[1399]

If the smell comes from sulfur you may chek if blooming is ocurring. (unreacted sulfur migrating to surface). You may try using non soluble amorphous sulfur and add it in a master batch at the end of mixing to reduce its heat history. You may try a combination of sulfur and acelerators sas these:sulfur:0.5 parts, TETD, TMTD, CBTS: 1 part


Also smell may come from plasticizer volatilization. You may check de type and level of plasticizer used:aromatic type plasticizer are the most comon for NBR, but they are volatile at certain temperature. If so, use a polymeric type plasticizer

Regards

Oscar Salazar

 

[berti]

Thanks 1399,

I will check first tip concerning insoluble sulfur and late adding of it.

Plastiziser is already a adipate polyester.

Will keep you informed about results.

Berti

 

[rubberdoc]

Nitrile rubber has a characteristic pungent odor and the smell may be unrelated to any of the compounding ingredients. You might try the test on the raw polymer to determine if that is the source of your problem. If so, you might be able to find a cleaner polymer (less residual monomer and non-polymer constituents). Also, a post cure often helps to drive off volatiles that could be affecting the test. Try baking the parts in a circulating air oven for several hours at 100C to 120C (higher than the temperature used for the odor test).
Jim