Thermoset prepreg matrix resins are semi-solid materials that provide ambient temperature tack and drape. The resins may be hot-melt filmed and combined with reinforcing fibers, direct coated onto fabrics, or solvated to make prepreg materials. These pre-engineered laminating materials have a discrete resin/fiber ratio that requires further lay-up of the continuous fiber plies to produce the composite part. The prepreg lay-up is then usually cured at elevated temperature and pressure.

Prepreg resins are usually supplied as single component semi-solid systems but API also has a range of two part (A/B) systems that can be filmed at ambient temperature, impregnated into the reinforcement, and react up at ambient conditions to provide stable tack levels. This type of material has many advantages for making low cost, high performance prepregs without the high cost associated with traditional prepreg machines. Likewise, wet-layup can be utilized to make prepregs that have stable tack levels and long out-times at ambient conditions. In addition to these products, API has an extensive number of hot-melt (and solvent) prepreg matrix products with unique balances of processing and properties.