Curing Agents for Epoxy: Amines, Anhydrides, and Mercaptans

Epoxy resin systems require a curing agent to convert the liquid epoxide into a thermoset network. The curing agent choice determines: pot life, cure schedule, Tg, mechanical properties, and chemical resistance.

Amine Curing Agents

Aliphatic Amines

• TETA/DETA: Fast cure, room temperature; pot life 20–45 min; Tg 90–120°C.
• IPDA (isophorone diamine): Slower cure (12–24h); better Tg (150–165°C); lower blush risk.

Aromatic Amines

• DDM: Tg 180–200°C; excellent elevated-temperature performance; suspected carcinogen (REACH restriction).
• DDS: Tg 200–230°C; aerospace grade.

Anhydride Curing Agents

Longer pot life (hours to days) and high Tg (150–180°C). Require elevated-temperature cure (120–180°C). Used in: electrical castings, filament winding, PCBs.

MTHPA (methyltetrahydrophthalic anhydride): Liquid; easy handling; Tg 130–150°C.

Mercaptan (Thiol) Curing Agents

Very fast cure; 5–30 min pot life at room temperature. Used for single-component adhesives and fast-setting applications. Limitation: unpleasant odor; lower Tg.

Selection Guide

Parameter	Aliphatic Amine	Anhydride	Thiol
Cure temp	RT	120–180°C	RT
Pot life	Short	Long	Very short
Tg (°C)	90–165	130–180	60–100
Chemical resistance	Good	Excellent	Moderate

HMEChem supplies aliphatic and cycloaliphatic amine curing agents, anhydride hardeners, and thiol systems.