WEST SYSTEM: How to mix G/flex epoxy with other WEST SYSTEM epoxies
WEST SYSTEM Epoxy is a very versatile system. 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 application. Here, we guide you through the method for mixing G/flex® epoxy with other WEST SYSTEM epoxies.
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.
Why use G/flex epoxy?
G/flex epoxy further expands the versatility of WEST SYSTEM Epoxy Products. G/flex epoxy can be used with WEST SYSTEM 105 Epoxy Resin® and one of its four standard hardener combinations – 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 epoxy, 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 below describes how properties will be affected when G/flex epoxy is blended with WEST SYSTEM Epoxy.
We have tested several mixtures of G/flex epoxy and WEST SYSTEM Epoxy mixtures 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 105 epoxy resin with any of the WEST SYSTEM hardeners (By volume G/flex epoxy 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 epoxy with G5 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 WEST SYSTEM EPOXY |
|
| More G/flex epoxy | More WEST SYSTEM 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 the material. 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 failing.
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. A tough, 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.
See Understanding Flexible Properties for a more complete discussion. For specific questions, contact our Technical Experts on the West System International support page.
This article first appeared in Epoxyworks on 26 February 2015.