Dihydrazides

Properties and Applications

Dihydrazides are a versatile and unique class of curing agents that are solid at room temperature and soluble in several protic solvents including water and acetic acid. They can cure a large variety of thermoset resins including epoxies, aldehydes, ketones, acrylamides, acrylates and isocyanates. This class of curatives offers many advantages over conventional curatives. For example, in one-part epoxy systems, they function as latent curatives with lower onset temperature than DICY while in urethane formulations, they offer reduced yellowing compared to conventional amines and in waterborne acrylic polymer emulsions, keto-hydrazide crosslinking provides high crosslink density with excellent performance including good color stability, long shelf-life, and good weather resistance.^1-5

The four most common dihydrazides are adipic dihydrazide (ADH), sebacic dihydrazide (SDH), isophthalic dihydrazide (IDH) and valine dihydrazide (VDH). The type of R group between the two hydrazide groups determines the physical and chemical properties such as melting point, solubility, miscibility, and chemical reactivity. For example, carbodihydrazide (CDH), with R simply a carbonyl group, is the fastest dihydrazide and is soluble in water and alcohol. Some common dihydrazides are represented in the Figure below.

Dihydrazides are used as latent curing agents for B-stageable epoxy resins, as chain extenders for urethane resins and as ambient crosslinkers for high performance acrylic and urethane emulsion products such as coatings, sizing agents, inks, sealants, and adhesives. Products crosslinked or cured with these compounds typically offer good weather resistance, low cure temperature and superior color stability when compared to many conventional curatives. They also have excellent storage stability when used as latent curatives in heat curable epoxy formulations or as crosslinkers in waterborne coatings and adhesives.⁶

Manufacturers & Distributors

Companies AjinomotoFine-Techno Ataman Chemicals ACCI Specialty Materials Gantrade

Brands Ajicure® 510-400 Technicure® ADH

 

¹US Patent 2847395A, Stable heat-curing epoxy resin compositions

²US Patent 5965673, Epoxy-terminated prepolymer of polyepoxide and diamine with curing agent

³US Patent 4412022, Polyurethane coating compositions prepared from a polymeric diol, an alicyclic diisocyanate, an alicyclic diamine and either hydrazine or isophthalic acid dihydrazide

⁴US Patent 4447571, Stabilization of polyurethanes

⁵Adipic Acid Dihydrazide – A Unique Crosslinking Agent and Curative, Gantrade's News & Industry Articles, November 3, 2020

⁶Dihydrazides can also be used as formaldehyde scavengers. They readily react with formaldehyde, thereby preventing formaldehyde to be released in the air.