One of my first big projects in industry after getting my Ph.D. in late 1970 was
the development of an analytical method to reverse-engineer sealants formulated
with a mixture of butyl rubber and polybutene.  See US2974377A to Kunkle of PPG.
JohnDeLand, FL

On Fri, 2020-05-01 at 23:19 +0000, Richard Koerner wrote:
>  Whatever it is...I love the stuff!  More than 30 years ago I decided to put a
> 14" square roofvent in my TinTop Vanagon....I love ventilation.  The kit for
> the roofvent came with some of that stuff.  Now, after 30 or more years in
> every condition....the stuff is Bomb-proof!  Never ever a leak, still looks
> the same after 30 years (meaning...can't see a thing, it's all underneath the
> flange).I bet you can go to almost any RV shop and get some of it.
> Righto...it is super duper sticky.  And super duper effective.  Good luck at
> ever trying to remove it though; will take a lot of patience and tools and
> solvents and elbow grease.
> RichSan Diego
>
>
>     On Friday, May 1, 2020, 3:59:17 PM PDT, David Beierl <dbeierl@gmail.com>
> wrote:    It's variously called mastic, dumdum, Thykol, butyl rubber.  May
> havedifferent compositions but what they have in common is non-hardening,non-
> shrinking etc.  The "tape" is a bit of a misnomer -- it's just a flatline of
> the stuff wrapped on releasing paper.
> Yrs,d
> On Fri, May 1, 2020 at 5:33 PM Steven Shelton <shelton4@gmail.com> wrote:
> > What is the black sticky stuff around the bolts in the pop-top roof?
> > Ithought it was butyl rubber but the only butyl rubber I can find is tape.
> > <
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