Sebacic Dihydrazide (SDH)

Sebacic Dihydrazide (SDH) is a long-chain aliphatic dihydrazide curing agent for epoxy resins, producing more flexible and tough cured systems than the shorter-chain ADH (adipic dihydrazide) due to the additional methylene groups in its 10-carbon sebacic backbone. SDH contains two active hydrazide groups (–NH–NH2) per molecule with an equivalent weight of approximately 115 g/eq. Like ADH, SDH provides excellent latency at ambient temperature in epoxy systems, activating above 100–120°C. The longer chain length of SDH compared to ADH results in lower crosslink density, higher elongation at break, and better low-temperature impact resistance in cured epoxy systems. SDH is used in specialty applications requiring toughened epoxy films, flexible coatings, and impact-resistant structural composites where room-temperature stability combined with moderate-temperature cure (100–140°C) is required. It is also used in waterborne systems, though its lower water solubility versus ADH may require co-solvents. Dosage is typically 12–18 phr on standard BPA epoxy. SDH is a white powder with good long-term stability and is classified with a favorable toxicological profile (no carcinogen classification).