Specialty Epoxies

By Don Gutzmer – GBI Technical Advisor

Why use a WEST SYSTEM specialty epoxy? I will cover the important characteristics of each of our three specialty epoxies. After reading this short article, you may see a use for one of these products in your future.

Six10 Adhesive

Six10 Thickened Epoxy Adhesive is a two-part epoxy with a consistency similar to gel toothpaste. We manufacture it under vacuum to prevent entrapped air bubbles. Our in-house chemists formulated this toughened system with 8% elongation. Conveniently, Six10 requires no hand mixing when used with a standard caulk gun and the static mixing wand that comes with each cartridge. The self-metering coaxial cartridge dispenses a gap-filling, structural adhesive that bonds tenaciously to wood, metals, fiberglass, and concrete.

To apply this adhesive to areas smaller than the tip of the static mixer, tape a small drinking straw to the end of the static mixer. Six10 has a working time of over 40 minutes until the mixing wand becomes unusable. This adhesive has shear thinning properties, which means it moves more like a liquid when you work the material. This allows its use in cooler temperatures. You can also use it to wet out lightweight fiberglass cloth. It will cure in temperatures as low as 50°F (10°C).

Six10 is an excellent choice for bonding in fasteners. With the ease of point-and-shoot application, Six10 Adhesive is hard to beat. Many boat owners realize that the convenience of not needing to hand-mix epoxy or add fillers outweighs the additional cost of Six10’s special packaging.

G/flex Epoxy

G/flex is a two-part, toughened epoxy that can make structural bonds which absorb the stress of expansion, contraction, shock, and vibration. We formulated this system for high elongation with an ultimate elongation of around 30%. The increase in elongation and lower modulus (stiffness) that it provides equates to better adhesion to substrates. This helps it resist a peel or delamination from starting.

G/flex has a 1:1 mix ratio by volume for easy measuring. It’s also ideal for bonding dissimilar materials. We offer it in two versions. The liquid version, G/flex 650, has a consistency similar to honey. You can thicken it with 406 Colloidal Silica to reach the same viscosity as the 655. The pre-thickened version, G/flex 655, has a consistency like gel toothpaste. With proper application techniques,it will bond to wet/damp substrates and dense or oily woods like teak and oak.

The lowest cure temperature for G/flex Epoxy is 40°F (4°C). These products provide about 45 minutes of working time at 72°F (22°C). G/flex will adhere to most plastics with proper surface preparation (see “Gluing Plastic with G/flex Epoxy” in Epoxyworks 26).

When you need to bond to a difficult substrate like teak or stainless steel, we recommend G/flex. Many boat owners see the benefits of using G/flex for repairs such as “Catalina Smile” hull-to-keel joint separations.

G/5 Five-Minute Adhesive

G/5 Five-Minute Adhesive is a two-part adhesive that will cure to a gel state within minutes. It has a 1:1 mix ratio by volume. You can wet sand it about 30 minutes after application. It is ideal for a temporary, quick cure that’s convenient for some applications like fabricating a quick custom sanding block with some scrap fiberglass cloth and a piece of foam.

G/5 should not be used where high loads are expected or if it will be continually immersed in water. A batch of mixed G/5 can be blended at different loadings with a WEST SYSTEM formulation to reduce cure time. It will speed the cure of 105 Resin and 205 Fast Hardener. Keep in mind that blending formulations will reduce physical properties and we don’t recommend it for certain applications. Thoroughly blend 105 / 205 at the proper mix ratio before adding blended G/5 resin and hardener to the mix.

Overall, these specialty epoxies have their advantages and expand the versatility of the WEST SYSTEM product line. The specialty epoxies are sold in larger volumes including gallon sizes and are also sold in small repair kits.