Alternatives to Santoprene 1

[twizel]

We manufacture 2 small ( 14mm dia. and 55mm dia) diaphragms from 70 Sh A Santoprene. Both diaphragms act as high flow dump valves. Both dump valves open only 500 times over the entire life of the product. One side of the valve is exposed to 70 PSi with the other side to atmosphere. .Operating pressures are approx. 60-70psi.

We are finding that they are suffering from a greater degree of compression set than expected. Both are injection molded.

Can anyone suggest a alternative material with good CS characteristics that can be injection molded?

thanks..

 

[GrahamBennett]

You could try peroxide cured EPDM-based or NBR-based compounds, which should have better compression set than the compound you are using at the moment.

 

[btrueblood]

With caution - neither of Graham's suggestions can be molded in standard plastic injection molding machines (which is the one thing Santoprene can do). The materials (EPDM, NBR) can be injection molded in machines specially designed/modified for rubber injection molding. I.e. the tooling you built for the thermoplastic Santoprene parts may not be usable for molding thermo-set rubbers.

 

[hainesc4]

What's the coldest temperature the product is going to see? If the temperature is low enough, you could see second order transition caused by thermal cooling. The molecules stiffen, and give poor CS rebound numbers. It would have to be pretty low of a temp. to see much effect.

 

[twizel]

HI Hainesc4. thanks for the reply.
operating temp is -20C > +40C.

thanks again

Craig

 

[rideac1]

Possibly silicone? Also requires as special liquid injection moldling machine and system. Silicone can be produced in the 70 Sh A but may be too flexible for the application.

 

[catastrafi]

I would suggest Monprene or Uniprene- available in a wide variety of grades - one is likely to meet your requirement

For example:

http://www.matweb.com/search/DataSheet.aspx?MatGUID=d12c2302e0d64e24a06d8ab92c07b76e

I can't really be more specific without knowing what compression set value are you looking for- can you advise?

 

[GrahamBennett]

Other alternatives are thermoplastic natural rubber (TPNR) and thermoplastic epoxidised natural rubber (TPENR) both of which contain natural rubber. Both can be injection moulded too.