[TowerTalk] RTVs.

[Roger (K8RI) on TT]

RTVs and what are they. "Room Temperature Vulcanizing"  (RTV)  is a 
generic term for family of sealant compounds that self vulcanize at room 
temperature..

AFAIK Nearly all Silicone RTVs are so close in formula that they might 
be considered the same.  I'm not familiar with all of them, but AFAIK 
the decision was made not to patent Silastic(TM) which is the original 
RTV.  The gamble was made that it would not be reverse engineered until 
well after the patent would have run out.
DAP

It was (at the time) a very profitable decision as it is relatively easy 
to make and The formula was not figured out until long after the patents 
would have expired.

I said "at the time" because the patent procedure has change from first 
to produce to first to patent.

If you remember many RTVs suddenly turning up, (IIRC a couple of decades 
ago) that would be right after it was figured out.  I believe that the 
Silastic(TM) RTV consumer line was sols when it became a low margin 
commodity.  I may be wrong, but I believe DAP sell the DC line of RTVs 
along with the Latex versions.  which are not from DC. As near as I can 
tell, DC still makes the RTVs and likely makes the consumer grades which 
others package and sell.  Who does what gets a little confusing.

http://www.dowcorning.com/content/etronics/etronicsseal/etronics_aas_1ptov.asp

All have a shelf life because they use moisture to cure. The tube will 
leak moisture at a very slow rate so they last a few years. Once opened, 
the screw on top is not that great a seal so their life after opening is 
at most, a few months.

Keep moisture away and the stuff lasts a very long time.  Thing is, the 
material has only been tested under what is considered "NORMAL STORAGE 
CONDITIONS" so the company is likely to say do not use beyond the 
expiration date.
.  I simply keep the tubes in a sealed Tupperware box/container/  "I 
think" the only requirement is that the container is moisture proof when 
closed.

I have used tubes that have been opened and resealed, 20 plus years 
after they were originally opened.  I have opened tubes for the first 
time that were 30 years past their original expiration date (that had 
been kept in the Tupperware box) and the result is still performing as 
advertized.

You CAN most likely use the Silastic(TM) RTV on antennas out doors with 
no problems as long as it is not in an enclosed space like a plastic 
antenna matching enclosure.

I have noted that with long duration storage (Over 20 years), the non 
acetic RTVs "MAY have some of the water/alcohol like substance separate 
out.  They still appear to work, but at that point, I pitched the tubes 
that had been opened.  I've observed no such problem with the acetic 
versions.

I used to get it at "The /Company Store" for pennies on the dollar. I'd 
get a bunch, put it in a plastic box and put it away.  I had a bunch of 
the high temp stuff, but gave all to nearby FBOs (Aircraft repair 
shops)  It came in BIG tubes as well as the 10 oz size,\.

Note, there are now "Latex" RTVs which appear to work well.  Note, these 
are water soluble until they have cured, so don't apply in the rain.

I hope this helps.

-- 

73

Roger (K8RI)