4,4'-Diaminodiphenylmethane (DDM/MDA)

4,4'-Diaminodiphenylmethane (DDM), also called MDA (methylenedianiline), is an aromatic diamine hardener for epoxy resins that produces cured systems with very high glass transition temperatures (Tg 140–160°C), exceptional mechanical properties, and superior chemical resistance compared to aliphatic amine curatives. DDM provides a low-viscosity, long-pot-life cure system when used in heated formulations (processing at 60–80°C to keep the solid dissolved), making it suitable for epoxy prepreg systems, filament winding, and structural aerospace laminates. Its AHEW is approximately 49.6 g/eq, requiring about 26 phr for standard BPA epoxy. DDM is the dominant hardener for several legacy aerospace prepreg systems and continues to be used in military and industrial composite applications. IMPORTANT: DDM is classified as a suspected human carcinogen (Category 1B under EU CLP) and is a regulated substance under REACH. Its use requires strict occupational health controls, exposure monitoring, and in the EU is subject to authorization requirements. Alternative aromatic amines or lower-hazard cycloaliphatic amines should be evaluated.