The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

Chapter 4 – WEST SYSTEM ® Products 27
blade performance life, we needed to learn more about
the long-term fatigue behavior of WEST SYSTEM epoxy.
Very little fatigue testing had been performed on epoxy
alone, and the long-term fatigue capability of the epoxy
in many composite applications was a question mark.
A number of different methods have been used to
test WEST SYSTEM epoxy in fatigue depending upon
specific needs for material design data to support wind
turbine blade efforts, and, in recent years, composite
design for marine architects and other boatbuilders.
While it is difficult to make general conclusions from
specific test data, it is apparent that WEST SYSTEM
epoxy exhibits good fatigue life and can maintain a
reasonable percentage of its one-time-to-failure load
capability after undergoing 10 million fatigue cycles.
(See Appendix C for further details.)
WEST SYSTEM ® Resin and Hardeners
<strong>The</strong> following product descriptions are subject to change.
Research and product development at <strong>Gougeon</strong> <strong>Brothers</strong>
is ongoing. As regulations, market demands, and technology
change, WEST SYSTEM products will change.
We will improve formulas, add new products, and drop
products as necessary. We recommend that you refer
to the current WEST SYSTEM User Manual & Product
Guide for up-to-date and more detailed product descriptions
and handling information.
105 Epoxy Resin is the base material of the WEST
SYSTEM family of products, on which all of WEST
SYSTEM compounds are built. <strong>The</strong> resin is a clear, pale
yellow, low-viscosity liquid epoxy resin. It is mixed with
WEST SYSTEM hardeners and cures at room temperature
to form a high-strength solid with excellent moisture
resistance. Hardeners are selected for their cure speed
and temperature range.
WEST SYSTEM epoxy is designed specifically to wet out
and bond with wood fiber, fiberglass, reinforcing
fabrics, and a variety of metals. It is an excellent adhesive
that will bridge gaps and fill voids when modified with
WEST SYSTEM fillers and can be sanded and shaped
when cured. With roller applications, it has excellent
thin-film characteristics to flow out and self-level without
“fisheyeing.” WEST SYSTEM epoxy cures clear, so you
can achieve a natural finish when coating with varnish.
It is formulated without volatile solvents and does not
shrink after curing. It has a relatively high flash point and
Figure 4-1 WEST SYSTEM resin and hardeners with mini pumps.
no strong solvent odor, making it safer to work with than
polyester or vinylester resins.
205 Fast Hardener is a medium-viscosity epoxy curing
agent. It is used in a majority of situations, at lower
temperatures—as low as 40°F (4°C)—and to produce a
rapid cure that develops its physical properties quickly
at room temperature. When mixed with the 105 Resin
in a five-parts resin to one-part hardener ratio, the cured
resin/hardener mixture yields a rigid, high-strength,
moisture-resistant solid with excellent bonding and
coating properties. Pot life at 72°F (22°C) is 9 to 12
minutes.
206 Slow Hardener is a low-viscosity epoxy curing
agent for use when extended working and cure time is
needed or to provide adequate working time at higher
temperatures. When combined with 105 Resin in a
five-parts resin to one-part hardener ratio, the cured
resin/hardener mixture yields a rigid, high-strength,
moisture-resistant solid with excellent bonding and
coating properties. Pot life at 72°F (22°C) is 20 to 25
minutes.
207 Special Coating Hardener was developed for
coating and fiberglass cloth application where an exceptionally
clear, moisture-resistant, natural wood finish is