Leon lcb11211@swbelldotnet wrote in
:

On 6/27/2014 12:22 PM, Michael wrote:
I've cut dados into 2 X 4 construction timber frames (lap joints) for
polycarbonate sections for a greenhouse-type structure (actually, a
solar wood kiln). I'm going to paint the frames before I assemble,
but while I'm at Home Depot to get the paint, I going to get some
calk to seal the frame (wood to polycarbonate) and I don't know if
your basic DAP polymer sealant is going to do the job. I don't know
if polycarbonate requires a special product, and I'm guessing the
structure is going to get pretty warm in the summer.

Thanks.



I have found the Butyl Robber sealant to hold up well and have great
stretch characteristics.


http://www.dap.com/product_details.a...=32&SubcatID=6


Polycarbonate is sensitive to many common solvents used in caulks and
sealants. You need to check the MSDS sheet of the proposed sealent
against the polycarbonate sheet manufacturer's technical guide if you
want to avoid microcracking and rapid degradation along the edge of the
sealent bead. The problem is significantly worse if exposed to UV.
However neutral cure silicones are generally safe.

Polycarbonate also has a high coefficient of thermal expansion so if the
grooves are too tight it will sheer the sealent. If loose enough to
allow for expansion, you then have the problem of shimming each sheet in
place so it is centered in the groove and doesn't bottom out anywhere.

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