NBR & ETHYL ALCOHOL SWELL
NBR & ETHYL ALCOHOL SWELL
(OP)
Need to get more swell out of a peroxide cured NBR compound for a gasket application. Best I've gotten is approx 2% change in thickness after 72 hr immersion at room temp in ethyl alcohol. Anything I can add to the compound to get more swell? I need about 4 to 6%. Thanks very much.





RE: NBR & ETHYL ALCOHOL SWELL
Lower the degree of crosslinking either through the peroxide level or cure conditions to get more swell. Increasing the free volume of the base resin with more branching will also help. This can also be done with plasticizers but they can leach out if in contact with a compatible solvent. Be careful.
Acetone or MEK will swell what you have more than EtOH.
RE: NBR & ETHYL ALCOHOL SWELL
RE: NBR & ETHYL ALCOHOL SWELL
Assuming the test sample is unrestrained the 2% thickness increase equates to a volume swell of ca 6% and the target will be equivalent to a 15% swell. The difference seems significant but please review the test conditions and measurements to ensure reproducibility is not a contributory factor, something I can speak about from experience. I take it the 'room temperature' is a standard lab temperature such as 23 C.