Calculations for Mixing Epoxy Formulations

Importance

• Performing the right calculations before beginning a job that requires epoxy is an essential part of the process. Without the right formulation, your epoxy will not have the strength you expect from it. This can make repairs ineffective or result in new construction that is prone to failure. The wrong epoxy formulation can also alter the curing time, which puts your project in danger. If you need to remove a failed epoxy application and start over, your job will end up taking longer and costing more.

Basic Ratio

• One of the most important calculations you need to make when you prepare an epoxy formulation involves the basic ratio of polyamine to epoxide. This ratio is generally based on weight rather than volume, which means you can't simply estimate the proportions based on the amount of each liquid you mix together. Most commercial epoxies come in pre-measured cartridges that make it easy to find the right ratio and create an epoxy that performs as expected.

Stoichiometric Ratio

• In some cases, an epoxies stoichiometric ratio is an added calculation. This ratio incorporates not only the weight of each chemical in the epoxy, but also the specific chemical composition of each ingredient. Stoichiometric ratio is especially important if you add material to an epoxy to alter its curing time or bonding properties. Chemists and engineers who work with epoxy use a series of complex chemical formulas to determine appropriate stoichiometric ratios.

Spread Rate

• The spread rate of an epoxy refers to how much surface a specific epoxy formulation will cover. This is useful when you use epoxy to seal a surface, such as a garage floor. Spread rate is typically measured in square feet and includes the coverage you can expect from the epoxy once it's mixed. Spread rate is combined with the basic ratio to determine how much epoxy to buy. For example, if the space you want to seal with epoxy is 300 square feet, and the epoxy you plan to use has a 100 square foot per gallon spread rate, you'll need a total of three gallons of epoxy. If the epoxy has a two-to-one polyamine to epoxide ratio, you'll need two gallons of the polyamine and one gallon of the epoxide.