Answer Terry Davey

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Posted by Bengt Blomberg on November 16, 2000 at 17:07:21:

Hello Davey,
As you know I was very interested in your technique.
However after your demo on the hull in Holland, and
after further tests on my own with similar equipment and
also with still stronger pumps, in every case I got the
same effect: The pthtallic acid does totalloy remain in
the laminate. The vacuum effect is like trying to suck
anything out of glass bottle without letting air in at
the same time. The heat makes uncured polyester in a number
of the outer laminate layers expand that the vacuum pump
sucks the expanded amount out. The acid is crystallic and
stays put. For the moisture, which also expands, the
"cold wall" effect becomes stronger than the vacuum effect
and the moisture moves invards. If the hull like the dutch
one has a soft coating on the inside, the moisture goes into
the coating otherwise it remains in the deepest laminate
layers. Then, depending on later temperature differences between
in- and outside, the moisture will either evaporate on the inside
or move back into the outer layers.
However the outer layers of a treated area will stay dry for a
few days and the difference when a peeler passes over a
slightly humid untreated area into the dry treated area
is very noticeable.
The problem is, that even if HotVac like HYAB can partly cure and
partly remove the uncured polyester neither of us can do anything
against the so called dangling chain molecules, which a
few days after the first curing in the mold no longer responds
to post curing by heat. By influence of the acid, these
dangling chains can be hydrolysed without presence of
styrene or uncured polyester enclosures.
Really Davey after we met and as I am really interested in finding
a technique which does not produce the sticky smell of
HYAB, I have spent a lot of time and a small fortune trying
to make your idea work properly, but the acid remains whatever
I have tried.
Regards Bengt

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