4,4'-Diaminodiphenylsulfone (DDS)

4,4'-Diaminodiphenylsulfone (DDS) is an aromatic amine hardener for high-performance epoxy systems, widely regarded as the preferred curative for aerospace composite structures where glass transition temperatures of 150–200°C are required. The sulfonyl group in DDS reduces electron density on the amine nitrogen, lowering reactivity compared to DDM/MDA — DDS requires cure temperatures of 120–180°C and extended post-cure schedules. This latent reactivity is valuable in prepreg systems, providing excellent out-of-freezer life and handling stability. DDS is the hardener of choice for leading aerospace epoxy prepreg systems and produces laminates with outstanding hot/wet retention of mechanical properties, which is critical for wing skin, fuselage, and structural aerospace panel applications. AHEW is approximately 62 g/eq, requiring about 33 phr for BPA epoxy. Unlike DDM, DDS has a better regulatory classification and is not listed as a carcinogen under REACH. It is a white powder with a high melting point (175–180°C) requiring dissolution in hot resin or use as a pre-dissolved master batch.