EPDM OR PU? WHICH IS BETTER?

[harmsgundam]

Hi All,

I would like to ask the opinions of you guys on which is the better material to be used as sealant for the sluice gate in our wastewater treatment facilities. Is it EPDM (ethylene propylene diene monomer (M-class) rubber) or Polyurethane type? The thing is of course this will be exposed to wastewater and its harmful chemicals so I want to ask for information which one is better and why? Hope to receive responses to anyone knowledgeable regarding this matter.

 

[Compositepro]

There are so many variations in formulation of rubbers in each category that there is no right answer. Urethanes in general do have the tendency to hydrolyze, meaning that they degrade by reacting with water. So, EPDM may be preferable. EPDM is also often used as a roofing material, which is similar to your application.

 

[btrueblood]

Like cpro said, EPDM is resistant to water and just about anything that can be dissolved in water (from sodium hydroxide to hydrochloric acid). On the other hand, urethane is much better at being resistant to abrasion (sand and particulates) and tramp oils, both of which might be issues for your wastewater gate. I am assuming you are looking for a manufactured seal, and not a caulking compound which is the first thing I think of when somebody says "sealant". If not, then urethanes, which can be poured and cured at room temperatures, are likely to make better (more durable mechanically) caulking compounds in a mechanism than roofing sealants and the like, formulated from epdm and solvents.

 

[tom1953]

If you're thinking polyurethanes, choose a polyether PU (ASTM designation EU), which is much more resistant to the effect of water than polyester polyurethanes (AU). Also, polyurethanes can be solid rubber materials ('millable polyurethane') as well as liquid, castable PU.