It looks like javascript is disabled. In order to use this site, you must have javascript enabled.
After enabling javascript, please click here or reload the page.
M
any a boatbuilder looking for a resin with improved
physical properties and better blister resistance has had
his interest piqued by glowing sales pitches promoting vinyl
esters. Most of these hopeful fabricators, however, have
quickly choked on the apparently steep price of improved
performance and said, "Thanks but no thanks." However, is
theirs the right assessment of the cost/benefit ratio associated
with this lesser-known breed of resin? Let''s take a look.
Developed in the 1950s, vinyl ester resins were first used
in fabricating corrosion-resistant tanks and piping for the
chemical industry. For industries needing a reservoir to hold
a few thousand gallons of
sulphuric acid, for instance,
tanks of composite construction
incorporating vinyl
ester resin cost much less
than units of glass-lined
stainless steel. In the marine
industry, the initial applications
of vinyl ester involved
high-performance maxi sailboats.
I remember seeing
friends returning from fairing
jobs on those vessels, shaking
their heads about the complexity of the three-component
chemistry of the early systems.
Since then, resin manufacturers have worked hard to
Because they are shorter and have
double-bond and ester linkage sites
only at their ends, vinyl ester molecules
are more flexible when cured
than their polyester counterparts,
thereby offering greater elongation.
friendliness."
But they
also offer low-density, superior
toughness, and—as mentioned—excellent corrosion
resistance. Boatbuilders need to be concerned with this last
characteristic because plain old water—whether fresh or salt—
is turning out to be rather nasty stuff for composites. Clearly,
if vinyl ester resins can protect a structural laminate from attack
by the likes of sulphuric acid, they can do wonders for
boats immersed in water.
Here, they are most commonly used in "barrier coats"
(immediately behind the
exterior gelcoat) to reduce
or eliminate osmotic blistering
problems. Vinyl esters are
becoming more common in
structural laminates, too,
because they offer more
strength, increased elongation,
and better damage/
fatigue resistance, especially
at high temperatures. In
comparative tests, the more
common polyesters that the
boat industry has used for so long simply come up short in
these categories.
modify vinyl esters so they handle like the familiar
stand-bys, ortho and iso polyesters. "Neat" resins into
which the boatbuilder had to blend catalyst, promoter, and
accelerator have largely been replaced by pre-promoted, preaccelerated
resins, catalyzed with methyl ethyl ketone peroxide
(MEKP), as are conventional polyesters. Moreover,
thixotropes (viscosity modifiers that help the resin stay put
during application) have been added to vinyl esters to adapt
them to boatbuilders'' spray-up and hand lay-up procedures.
Vinyl ester resins are now gaining acceptance among
marine manufacturers, in part because of this new "user10
PROFESSIONAL BOATBUILDER
Basic Chemistry
Vinyl esters fall somewhere between polyesters and
epoxies in their chemistry, incorporating many of the basic
feedstocks of both resin families. Unlike polyester resins,
which are the product of reactions between either orthophthalic
or isophthalic acid and maleic anhydride, vinyl
esters are the result of reactions between bisphenol-A epoxy
and methacrylic acid. As is the case with polyesters, styrene
monomer is the reactive diluent for the resin. However, though
vinyl ester resin may smell and appear just like generalpurpose
(GP) ortho polyester, what emerges from the
Right click(Command + click) your mouse on the magazine pages to pop up a Quick Menu of the most used reader features:
To open up additional features, hover over or click on the arrow on the left. You can pin this pull-out menu to have it remain visible (or close by clicking on the push pin ). Included in this tab:
A: Our print feature relies on your web browser's print functionality - and how that browser communicates with your specific printer. If you note that pages are getting cut off, or you are having other issues when printing, it is likely that you need to adjust your printer's settings to scale to fit page.
Alternatively, if there is a PDF Download option available you can download the PDF first and then print using Adobe Acrobat Reader’s print feature. There are known issues in printing fom Internet Explorer 7, so if you are using this browser, you may wish to try a different one. If you are able to print from your browser normally but are having issues specifically with printing pages from the magazine, then please contact technical support.
Thank you for sampling the digital edition of Professional BoatBuilder To continue reading this issue, you must be a subscriber.
If you are a subscriber, you must log-in before you can continue viewing the digital edition.
Click here to log-in
If you are not yet a subscriber:
Click here to join.