TheSamba.com :: View topic

Mon Aug 18, 2008 10:22 pm

My mirrors, I bought from WW about 6 months ago are great but the rubber around them is getting soft and gooey. Is this normal and I'll need to replace the rubber? I drive it every day but isn't left out overnight.

Tue Aug 19, 2008 7:37 am

Clean it with acetone and put car wax on it or just car wax it. It'll keep doing that over the years. I'd guess the real ears had more of a natural rubber surround.

Tue Aug 19, 2008 7:43 am

Throw them in the trash where they belong and buy reproduction stock mirrors from this guy:

http://www.thesamba.com/vw/classifieds/detail.php?id=478014

They are very, very good quality. Much better than the arms and mirrors I bought from WW several years ago.

Tue Aug 19, 2008 10:53 am

The sun makes them gooey.

Tue Aug 19, 2008 1:01 pm

If I had to guess, I would say this is caused by oxidation resulting in chain cleavage, and that this IS a natural rubber article.

Oxidation is a free radical chain process. Once it starts it will continue to “un-zip” the polymeric backbone killing physical proerties. In most rubbers (EPDM, SBR, etc) oxidation causes stiffening due to increased cross-link density. With natural rubber, softening occurs because further crosslinking is hindered by a bulky methyl side group. Thus chain cleavage leading to lower molecular weight, and yes SOFTENING.

Wax is used in a rubber compound to migrate to the surface and protect the article. If the wax is compatible it will not migrate, and will not protect.

Adding wax to your mirror rubber may help in the short term, but the process has already begun.

EPDM is the preferred elastomer for outdoor exposure then and now and is likely the basis for most rubber components in an old VW.

The efficient Ziegler-Natta catalyst system used to efficiently polymerize EPDM, is named after a German Ziegler and an Italian Natta.

Tue Aug 19, 2008 5:55 pm

DownRiver wrote: If I had to guess, I would say this is caused by oxidation resulting in chain cleavage, and that this IS a natural rubber article.

Oxidation is a free radical chain process. Once it starts it will continue to “un-zip” the polymeric backbone killing physical proerties. In most rubbers (EPDM, SBR, etc) oxidation causes stiffening due to increased cross-link density. With natural rubber, softening occurs because further crosslinking is hindered by a bulky methyl side group. Thus chain cleavage leading to lower molecular weight, and yes SOFTENING.

Wax is used in a rubber compound to migrate to the surface and protect the article. If the wax is compatible it will not migrate, and will not protect.

Adding wax to your mirror rubber may help in the short term, but the process has already begun.

EPDM is the preferred elastomer for outdoor exposure then and now and is likely the basis for most rubber components in an old VW.

The efficient Ziegler-Natta catalyst system used to efficiently polymerize EPDM, is named after a German Ziegler and an Italian Natta.

this was my exact thought, i was just consulting you guys to see if my instincs were correct. Weird thing is though, it's only happening to one of them. :?