By Jeff Wright
West System 105 Resin-based epoxy
is a very versatile system. For
years, experienced users have been
blending the various products in
countless ways. For example, users
may blend 205 Fast Hardener and
206 Slow Hardener to make a hardener
with a modified cure speed.
Different uses of 410 Microlight
Filler provide a further example.
Many customers assume that the
only use of 410 is to make a fairing
compound it is added to thicken
epoxy to a peanut butter consistency
to create a light, easily-sanded filler.
However, 410 Microlight can be
used in other ways. Jon Staudacher
in Epoxyworks 22 described how he applied a runny mixture of epoxy and 410 to fill the weave on a composite part and reduce the amount of fairing required. Epoxyworks 25 described how 410 was added to
make a flexible epoxy that would allow
hardware to be removed easily
and yet would seal out water; this
was needed for installing a removable
hatch. As these examples illustrate,
experienced customers know
that by understanding the fundamental
characteristics of West
System fillers, hardeners, and additives,
they can combine and use
them in unique ways for their specific
G/flex further expands the versatility
of West System 105 Resin-based
epoxies. G/flex can be used with 105
Resin and one of its four standard
hardeners (205 Fast, 206 Slow, 207 Special Clear or 209 Extra Slow) to
modify its cured properties. For example,
you may want the tough and
flexible properties of a G/flex laminate,
but G/flex 650 will not easily
wet out the heavier fabric being
used. Adding a 105 Resin-based
epoxy mixture to a G/flex epoxy
mixture will greatly improve the
G/flex epoxy's ability to wet out
When G/flex is mixed with 105
Resin-based epoxy, the properties will
reflect the characteristics of both systems.
As G/flex is added to a 105
Resin combination, the resulting
cured epoxy will be more flexible and
able to deflect more before cracking,
but it will also have slightly lower
strength. With G/flex, the decrease in
strength is not nearly as much as
when a low-density filler is used, but
the change in flexibility does affect
ultimate strength. The table describes
how properties will be affected when
G/flex is blended with a WEST
SYSTEM 105 Resin-based epoxy.
We have tested several mixtures of
G/flex and 105 Resin-based epoxy in
a wide range of physical tests. The
blended systems have properties that
are proportional to the ratio of each
product in the final mixture. Experienced
WEST SYSTEM users can follow
their intuition to decide what ratio of
each system they would like to blend
together, much as they do when adding
fillers. Remember however, you
must follow the correct ratio for each
system when mixing any of the WEST
SYSTEM resins and hardeners.(G/flex
is 1:1, 105/205 or 206 is 5:1,
105/207 or 209 is 3:1). If the ratios
are correct, it's not necessary to mix
each system separately before mixing
the two systems together.
The same principle applies to blending
G/flex with G/5 Five-Minute Adhesive.
In this case you will trade
flexibility and strength for cure
speed in proportion to the percent
of each in the mixture.
Cured characteristics of blended G/flex 650 epoxy and 105 Resin-based epoxy
|More G/flex epoxy
||More 105 Resin-based epoxy
|More Flexibility|| Less Flexibility|
|Less Strength ||More Strength|
|More Elongation ||Less Elongation|
|More Toughness ||Less Toughness|
|More Viscosity ||Less Viscosity|
Definitions of the terms used in the table
Flexibility-The flexibility of a material is described by its
Modulus of Elasticity. The larger the value, the stiffer thematerial.
It is important to remember that the stiffness is not related to the
strength of the material. Stiffness is the physical property that determines how much a component will deflect when loaded.
Strength-The amount of stress a material can sustain without
Elongation-How much a material stretches when loaded and is
often written as a percentage of its original length. The ultimate
elongation is the amount it has stretched when it fails.
Toughness-How well a material resists fracturing when it is
stressed.Although, strong material resists fracturing and is able to absorb
energy. A very strong material may be brittle and unable to absorb
energy while an extremely flexible material will not absorb
energy because it will deform instead of carrying the applied load.
Viscosity-The resistance a liquid has to flow. This property does
not affect the cured properties, but is important for application. A
lower viscosity material will generally wet out a fabric easily, but will
not fill a gap well in a bonding application.
Copyright 2002, Gougeon Brothers, Inc. All rights reserved.
Epoxyworks 18 / Fall 2001
Last Modified on 10/28/02.
Reproduction in any form, in whole or in part, is expressly forbidden without the consent of the publisher. EPOXYWORKS, Gougeon Brothers, WEST SYSTEM, Episize, Scarffer and Microlight as used throughout this publication, are trademarks of Gougeon Brothers, Inc., Bay City, Michigan, USA.