Sika 721-UV to be replaced by Sika 505-UV??
I have removed all the old selant around my vents and was planning on using gray Sika 721-uv. I have half a tube left but I can't find it anymore. Airstream looks at me like I'm crazy when I ask for the gray since they stock white 721-uv. I emailed Sika today and here was there response if anybody is interested (sorry if this is old news):
Sika 721UV was replaced by Sika 505UV last year. Sika has been selling Sika 505UV since 2008, and they are not different enough to sell both. The last Sika 721UV made, should be expired by now.
The Airstream factory and others users have switched to Sika 505UV. Both are very good and similar products, of a type known as "silane-terminated polymer." Silane is a popular and proven adhesion promoter, especially effective on bare metals. Both 721UV and 505UV perform similarly in long-term durability.
One difference, is that even fully cured, the surface of 721UV had a permanent tacky feel. Sika 505UV does not.
If you Google "Sikaflex 505UV" you will see a number of distributors advertising it. On a bare aluminum surface like Airstreams, I would definitely use Sika 721UV or 505UV and not some other.
My question is, has anybody used the 505-UV? I'm assuming since the manufacture recommeded it, I'll be fine. I can get it fairly close to my house and about $6 less a tube than the white 721-uv from the Airstream dealer. I'm reluctant to use my gray 221 on the roof. Thanks!