Originally Posted by azdryheat
tomato, tomahto. They're both rubber. One is smooth, the other textured. Don't think it matters. Or does it? My 3600 has EPDM on the roof.
Totally different products. TPO is Thermo Poly Olefin, basically a form of heat formed plastic. EPDM is Ethylene Propylene Diene Monomer which is a synthetic rubber. They require different types of sealants. FWIW the TPO is better at UV resistance than EPDM. Also when new most TPO can be thermal welded, EPDM cannot. TPO is resistant to oil based chemicals (diesel residue), while EPDM will deteriorate when exposed to them.
TPO doesn't stretch as much as EPDM either. They both have their place in the market, though I strongly suspect that EPDM was primarily used because it was cheaper.
If I had to chose between the two for an RV roof I would prefer the TPO. That being said, when the time comes for my roof upgrade I plan on going with the Flex Armor spray on roof, seems to be the best bang for the buck when it comes to reroofing. The alternative will be a PVC/Kee based sheet material called Fibertite. Not normally available for RV roofs.