[Public-List] Butyl and Polycarbonate

Bill Wallace via Public-List public-list at lists.alberg30.org
Tue Oct 7 06:45:27 PDT 2014

If you read those lists, things like butyl acetate are problems, but the chemical in butyl tape, isobutyl isn't listed as a problem.  That isn't definitive, as I couldn't find a positive statement about isobutyl being safe.  If you are using polycarbonate, expect to redo the portlights every 5-7 years.  That is what I was replacing and mine were nearly opaque after about 8 years.   I will watch mine and see if there are any problems, but so far after 1 summer they look good with the butyl tape - it isn't clear how long it would take to react if there is going to be a problem.  For sure, cleaning up butyl is far easier than cleaning silicone, so if I have to replace them in a few years, it will be a much small job than the first replacement was.


On Monday, October 6, 2014 4:29 PM, Greg Bover via Public-List <public-list at lists.alberg30.org> wrote:

When I redid my port lights a few years ago it wasn't because they leaked,
it was because I couldn't see out of them anymore because of fogging. When I
got the boat they were an unknown plastic and caulked with what appeared to
be butyl. I use polycarbonate in my business and I knew that it was subject
to embrittlement and fogging when exposed to certain chemicals. I did some
research and found lists like the ones at
www.palramhort.com/pdffiles/PC...Info/PC_Chemical_Resistance.pdf  and
As there are various sorts of butyl and butyl compounds on the lists of
chemicals to avoid in contact with polycarbonate I opted to use a Dow UV
resistant silicone. I had to do quite a bit of masking to make a neat job of
it, but so far, (two years) it has held up well with no sign of fogging.
It seemed to me that the best combination would have been safety glass with
butyl, but the estimate for just the glass for the four larger ports was
$250, whereas I could use off cuts from my shop for nothing. Ahh.life on a

Greg Bover
A-30 #114

Gregory R Bover
V.P. Operations, Project Manager
C. B. Fisk, Inc.
978 283 1909

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