Consisting of a resin and a hardener, a two-component epoxy can be formulated to offer a wide range of mechanical, thermal and electrical properties. While mix ratios differ, they all offer the ability to cure at ambient temperatures or elevated temperatures for faster cures. Here are a few tips to help you mix and apply your two-part epoxy.

Steps to Apply a Two-part Epoxy Adhesives

1^st. Materials

First, you will need to get all your materials and safety equipment in place.

• disposable gloves
• safety glasses
• weight scale or volumetric cups
• mixing stick (preferably metal)
• part A and part B epoxy adhesives

2^nd. Surface Preparation

Surface preparation is as important as the epoxy adhesive itself. You should make sure the surfaces you intend to adhere are free of contaminants. The biggest problem with adhesives is substrate cleanliness. Whenever possible, the surfaces should be abraded or wiped down with a cleaning solvent before the epoxy is applied. Oil on the surface of steel or even oil from fingerprints can ruin a bond. For added adhesion, plastic surfaces can be abraded, or flame/corona treated to remove any plasticizer. 

3^rd. Mixing the Epoxy Adhesives

Several methods exist for proper mixing; three are detailed below.

•  Hand mixing is typically used for prototyping or low-volume production. This is not a method recommended for medium to higher levels of production. If you do hand mix, it is best to pour the resin (part A) into the mixing vessel first. The product should be weighed to the nearest gram. The hardener (part B) should be added next, using the same weighing procedure. Using a stir stick, mix the product for at least three minutes, scraping the sides and bottom of the vessel frequently. Avoid whipping the material to minimize air being introduced into the mix. After the epoxy has been thoroughly combined, the mixture should be poured into the mold or used in the adhesive step. If you do plan to hand mix, you should choose an epoxy with a long open time (pot life) so you have plenty of time to mix and pour into your application.

• Cartridge mixing is used for medium to large production runs. This method requires the two-part epoxy to be pre-packaged in side-by-side cartridges. Most HumiSeal adhesives or encapsulants formulas come in 1:1, 2:1 volume ratios, making them ideal for side-by-side cartridge packaging. Some of the more common sizes for side-by-side cartridges are 50, 200, 400 and 1500ml. When choosing a cartridge size, you should consider shot size, pot life, quantity of parts to be processed and ergonomics of the job. When using cartridges above 600ml, the use of a pneumatic gun is highly recommended due to the ease of use created by the higher dispense pressures.

• Meter mix equipment is used for high-volume applications. There are several equipment manufacturers in the industry. One of the more important things to do when choosing equipment is to make sure the plumbing is compatible with the epoxies being dispensed. Check with your epoxy manufacturer to confirm if any types of plastics or metals can negatively affect your epoxy.

4^th.Curing Your Two-Part Epoxy Adhesives

Fortunately, your two-component epoxy will cure by exothermic chemical reaction when properly mixed.  You can allow the mixed epoxy to cure at room temperature or accelerate the process with heat. Cure rates are usually stated at a certain temperature and at a certain mass of material (e.g., 25 minutes in a 100-gram mass). If you are working with a larger mass, the cure time will be shorter. Lower masses and thin films will take much longer to cure. 

When properly mixed and cured, two-part epoxies can add a great deal of protection to your products. If you have any questions or need help with your application, please contact us at techsupport@humiseal.com.

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