Epoxy resin system for structural composites

A slow reacting epoxy resin system comprising:

• a high purity epoxy resin component selected from a high purity Bisphenol A (BPA) epoxy resin, a high purity Bisphenol F (BPF) epoxy resin, and a combination thereof, wherein the high purity epoxy resin component comprises less than 5000 ppm of has by-products and impurities;
• an amine curing agent comprising a first linear aliphatic amine and a second linear aliphatic amine, wherein the first linear aliphatic amine is present in an amount of at least 72 wt. %, based on the total weight of the amine curing agent, and the second linear aliphatic amine, which is different from the first linear aliphatic amine, is present in an amount of at most 14 wt. %, based on the total weight of the amine curing agent, and
• optional additives selected from the group consisting of modifiers, diluents, and a combination thereof;
• wherein the initial viscosity after mixing the high purity epoxy resin component and the amine curing agent without the optional additives is less than 350 mPa·s at 25° C., as measured in accordance with ASTM D2196;
• wherein the initial viscosity after mixing the high purity epoxy resin component and the amine curing agent with the optional additives is from 150 to 250 mPa·s at 25° C., as measured in accordance with ASTM D2196;
• and wherein the viscosity of the slow reacting epoxy resin system reaches 1000 mPa·s at 30° C. after a period of greater than 198 minutes, as measured in accordance with ISO 3219.