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Adipic acid dihydrazide=Adipohydrazide,Adipyl hydrazide
CAS Number: 1071-93-8
Chemical formula: C6H14N4O2
Adipic acid dihydrazide (ADH) is a chemical used for cross-linking water-based emulsions. It can also be used as a hardener for certain epoxy resins.
ADH is a symmetrical molecule with a C4 backbone and the reactive group is C=ONHNH2.
Dihydrazides are made by the reaction of an organic acid with hydrazine.
Other dihydrazides with different backbones are also common, including isophthalic dihydrazide (IDH) and sebacic dihydrazide (SDH).
Adipic acid dihydrazide (ADH) is an effective crosslinking agent, curative and hardener.
It is the most common dihydrazide crosslinking agent within a series of dihydrazides such as sebacic dihydrazide (SDH) and isophthalic dihydrazide (IDH).
ADH’s has a melting point of 180 °C and a molecular weight of 174; both are lower than the alternative dihydrazides SDH and IDH.
Adipic dihydrazide is used as a difunctional crosslinking agent in paints and coatings for certain water-based acrylic emulsions.
It is used as a hardener for epoxy resins and a chain extender for polyurethanes.
A small use is as a formaldehyde scavenger preventing the liberation of formaldehyde.
Epoxy Resins
The first thing to note with ADH in epoxy formulations is that each of the primary amine end groups has a functionality of two, so the ADH molecule has an equivalency of four per epoxy moiety.
Accordingly, the active hydrogen equivalent weight of ADH is 43.5.
When formulated with epoxy resins, the ADH index can range between 0.85-1.15 of stoichiometric proportions, without a significant effect on mechanical properties.
The cure temperature for epoxy resins (glycidyl types) formulated with ADH is influenced by the melt-out temperature of the ADH, which allows an extended pot life at low temperatures.
Storage stability can be up to six-months at room temperature, with cure times of about one-hour at 130 °C.
Cure rates can be accelerated using tin or titanate catalysts, or imidazoles.
One-component ADH epoxy systems can be partially cured or “B-staged”, and later fully cured.
B-staging provides handling, processing, and fabrication advantages. One component epoxy resins are used in coatings such as powder coatings, adhesives including hot melt adhesives, molding compounds and in fiber reinforced composites.
Glass and carbon fiber prepreg obtained by a hot melt impregnation method are used in the fabrication of sporting goods, wind turbine blades and aircraft/aerospace components.
With ADH cure, epoxy resins exhibit excellent toughness, flexibility, and adhesive properties. Tg’s of 140-160 °C are achievable using a standard liquid bisphenol A epoxy resin (DGEBA) with ADH as the hardener.
Rigid and flexible epoxy adhesives have been formulated as one component systems that can be stored at room temperature using ADH as a latent curing agent.
Rigid epoxy adhesives are based on bisphenol A and novolac epoxides.
These rigid adhesives exhibit excellent cohesive and adhesive properties to a wide variety of surfaces.
Flexible epoxy adhesives produce more pliable bonds which better accommodate bond line stresses or differential substrate expansion rates.
Flexible epoxy resins include aliphatic di- and tri-epoxy resins such as hexanediol diglycidyl ether and poly(oxypropylene) diglycidyl ethers.
Semi-rigid epoxy-based adhesives utilize mixtures of both classes of epoxy resins or rigid formulations using flexibilizers.
Polyurethane Dispersions (PUDs)
ADH is an effective room temperature curative for aqueous PUDs and solution polyurethanes.
In this capacity, ADH provides polyurea coatings with higher hardness, toughness and adhesion properties, excellent mechanical properties, abrasion and chemical resistance.
ADH cured polyurethane coatings exhibit good color stability and weathering properties, which is not observed with standard amine curatives.
ADH is added to the water phase in a PUD.
Crosslinking occurs during the drying and film coalescence process which is ideal for maximizing the film properties including gloss, scrub, stain and wear resistance and durability.
Other crosslinking methods where crosslinking occurs prior to film coalescence exhibit reduced performance properties including poor flow and leveling.
The full reactivity characteristics of ADH are ideal for PUR systems.
Alternative curatives which show incomplete crosslinking due to slow reactivity and the lack of curative mobility in a dry film will also compromise performance.
Acrylic Resins
The leading crosslinking technology for acrylic emulsion polymers is ambient temperature crosslinking chemistry based on diacetone acrylamide (DAAM) or acetoacetoxyethyl methacrylate (AAEM) and adipic acid dihydrazide (ADH) monomers.
This technology, known as “keto-hydrazide crosslinking,” involves the direct reaction of the pendant ketone moiety on the DAAM-acrylic or AAEM acrylic polymer segment and the hydrazide moiety of the ADH, with the evaporation of water in the film-forming process.
This self-crosslinking technology has been adopted in high-durability paints and coatings for architecture, wood, and concrete surfaces, and more.
The DAAM/ADH pair is also used in crosslinkable sizing agents, thickeners, adhesives, and sealants.
The DAAM/ADH and AAEM/ADH crosslinking system provides several key benefits for formulators and consumers, from reducing safety concerns to improving performance properties and much more.
These benefits include:
Diacetone acrylamide and acetoacetoxyethyl methacrylate uniformly copolymerize within acrylic copolymers, creating well-dispersed pendant ketone crosslinking sites.
Wet acrylic emulsions based on DAAM or AAEM with ADH in the aqueous phase are initially non-reactive and afford emulsions with good long-term stability during shipping and storage in retail containers (also known as "in-can" stability).
After film coalescence, crosslinking becomes rapid at ambient temperatures, thanks to water evaporation in the drying process and a reduction in pH from the loss of ammonia.
Because crosslinking is post-coalescence, the resulting three-dimensional polymer network exhibits enhanced mechanical strength and durability as well as maximum film cohesive properties.
Crosslinking with the keto-hydrazide chemistry enhances abrasion, scrub, stain, and blocking resistance; moisture and solvent resistance; and substrate adhesion.
With other crosslinking chemistries, premature crosslinking occurs within the emulsion particles prior to coalescence, thus retarding intermolecular diffusion between emulsion particles and resulting in weaker film products and coatings. This dynamic occurs especially when diacrylates are used in the copolymerization recipe to produce crosslinks.
Both intermediates are formaldehyde free, unlike melamine crosslinking chemistries. DAAM and ADH are easily dissolved in warm water and in many other monomers. Finally, the by-product of the crosslinking reaction is water.
Conclusions
Adipic dihydrazide is a unique crosslinking agent and curative, offering controlled reactivity and performance enhancements in epoxy resins, polyurethane dispersions (PUDs), solvent based PURs and emulsion acrylic resins.
The major applications for ADH are a latent curing agent for B-stageable epoxy resins and an ambient temperature crosslinking agent for high performance acrylic emulsion architectural coatings.
Systems crosslinked or cured with ADH exhibit good color stability and weathering characteristics, adhesion, durability, hardness, and toughness.
APPLICATIONS
Adipic acid dihydrazide is a homobifunctional cross-linking reagent specific for aldehydes resulting in relatively stable hydrazone linkages.
Adipic acid dihydrazide is typically, used in the linking of glycoproteins, such as antibodies, in a site specific fashion following periodate oxidation.
Oxidation and coupling may conveniently be performed at pH 5.0 due to the low pKa of the hydrazide which avoids competition by primary amines.
Room temperature crosslinkable waterborne coatings .
Acryl emulsion comprising acryl monomers and diacetone acrylamide crosslinks with amino groups of ADH very rapidly.
The coating has excellent water resistance.
Formaldehyde scavenger.
ADH reacts with formaldehyde and prevents volatilizing of formaldehyde in the air. Epoxy resin hardener; ADH reacts with epoxy resin at high temperature and is useful for powder coating. Reforming of plastic and fiber processing.
ADH is widely applied in the decorative powder, insulation powder, fire retardent powder, electricals powder, heavy-duty powders.
Particularly in the manufacturing high-quality heavy-duty high-temperature fast-curing powder and oil pipelines, aerospace, aviation fuel, and other areas, it acts as essential potential curing agent.
It also has the features to increase strength in epoxy powders and UPR products with very satisfactory results.
INDUSTRY USES
Intermediates
Paint additives and coating additives not described by other categories, Paints and Coatings.
About Adipic acid dihydrazide
Adipic acid dihydrazide is registered under the REACH Regulation and is manufactured in and / or imported to the European Economic Area, at ≥ 1 000 to < 10 000 tonnes per annum.
Adipic acid dihydrazide is used by consumers, in articles, by professional workers (widespread uses), in formulation or re-packing, at industrial sites and in manufacturing.
Consumer Uses
Adipic acid dihydrazide is used in the following products: coating products, adhesives and sealants, fillers, putties, plasters, modelling clay, finger paints, polymers, non-metal-surface treatment products, textile treatment products and dyes and washing & cleaning products.
Other release to the environment of this substance is likely to occur from: outdoor use, indoor use (e.g. machine wash liquids/detergents, automotive care products, paints and coating or adhesives, fragrances and air fresheners), indoor use in close systems with minimal release (e.g. cooling liquids in refrigerators, oil-based electric heaters) and outdoor use in close systems with minimal release (e.g. hydraulic liquids in automotive suspension, lubricants in motor oil and break fluids).
Article service life
Other release to the environment of this substance is likely to occur from: outdoor use in long-life materials with low release rate (e.g. metal, wooden and plastic construction and building materials) and indoor use in long-life materials with low release rate (e.g. flooring, furniture, toys, construction materials, curtains, foot-wear, leather products, paper and cardboard products, electronic equipment).
This substance can be found in complex articles, with no release intended: vehicles covered by End of Life Vehicles (ELV) directive (e.g. personal vehicles or delivery vans).
Widespread uses by professional workers
Adipic acid dihydrazide is used in the following products: adhesives and sealants, coating products, paper chemicals and dyes, textile treatment products and dyes and washing & cleaning products.
Adipic acid dihydrazide is used for the manufacture of: textile, leather or fur and wood and wood products.
Other release to the environment of this substance is likely to occur from: outdoor use, indoor use (e.g. machine wash liquids/detergents, automotive care products, paints and coating or adhesives, fragrances and air fresheners), indoor use in close systems with minimal release (e.g. cooling liquids in refrigerators, oil-based electric heaters) and outdoor use in close systems with minimal release (e.g. hydraulic liquids in automotive suspension, lubricants in motor oil and break fluids).
Formulation or re-packing
Adipic acid dihydrazide is used in the following products: adhesives and sealants, coating products, fillers, putties, plasters, modelling clay, polymers, textile treatment products and dyes and finger paints.
Release to the environment of adipic acid dihydrazide can occur from industrial use: formulation of mixtures and formulation in materials.
Uses at industrial sites
Adipic acid dihydrazide is used in the following products: paper chemicals and dyes, coating products, textile treatment products and dyes, adhesives and sealants, finger paints, laboratory chemicals, washing & cleaning products and water treatment chemicals.
Adipic acid dihydrazide is used for the manufacture of: chemicals, pulp, paper and paper products, plastic products and textile, leather or fur.
Release to the environment of this substance can occur from industrial use: for thermoplastic manufacture, as an intermediate step in further manufacturing of another substance (use of intermediates), in the production of articles and as processing aid.
Manufacture
Release to the environment of this substance can occur from industrial use: manufacturing of the substance.
Abstract
Adipic acid dihydrazide (ADH) as one of the most widely used homobifunctional linkers in bioconjugate chemistry was used to prepare active forms of originally neutral mannans from the three pathogenic yeasts (Candida albicans, Candida tropicalis, Candida glabrata).
A combination of the simple analytical methods (elemental analysis, colorimetric assays: Park–Johnson assay, trinitrobenzenesulfonic acid assay, and size exclusion chromatography) was applied for exhaustive structural characterization of the products.
Significant cross-linking effect of ADH was revealed, despite the high excess of ADH involved in the reaction.
PROPERTIES
Appearance: White Crystals
Formula: C6H14N4O2
Mol.weight: 174.2
Purity: MİN. 98%
Loss on drying: max. O.4%
Melting Point: 177-184 C
Solubility in Water: 9.1 g / water at 20 C
Specific Gravity: 1.25 g / cm3
Boiling point 426°C
Melting point 181°C
Ignition temperature 360°C
Density at 20°C 1.29 g/cm3
XLogP3-AA: -2.1
Hydrogen Bond Donor Count: 4
Hydrogen Bond Acceptor Count: 4
Rotatable Bond Count: 5
Rotatable Bond Count: 174.11167570
Monoisotopic Mass: 174.11167570
Topological Polar Surface Area: 110 Ų
Heavy Atom Count: 12
Formal Charge: 0
Complexity: 142
Isotope Atom Count: 0
Defined Atom Stereocenter Count: 0
Undefined Atom Stereocenter Count: 0
Defined Bond Stereocenter Count: 0
Undefined Bond Stereocenter Count: 0
Covalently-Bonded Unit Count: 1
Compound Is Canonicalized: Yes
CAS Name
Adipic dihydrazide
Molecular Formula
C6H14N4O2
Molecular Mass
174.20
InChI
InChI=1S/C6H14N4O2/c7-9-5(11)3-1-2-4-6(12)10-8/h1-4,7-8H2,(H,9,11)(H,10,12)
InChIKey
InChIKey=IBVAQQYNSHJXBV-UHFFFAOYSA-N
SMILES: C(CCCC(NN)=O)C(NN)=O
Canonical SMILES: O=C(NN)CCCCC(=O)NN
Other Names of Adipic acid dihydrazide
Hexanedioic acid, 1,6-dihydrazide
Adipic acid, dihydrazide
Hexanedioic acid, dihydrazide
Adipic dihydrazide
Adipoyl hydrazide
ADH
Adipoyl dihydrazide
Adipoyldihydrazine
Qualimer ADH
BT 1000Z
BK 1000Z
NSC 29542
NSC 3378
ADH 4S
ADH (hydrazide)
ADH-J
ADH-S
T 2210
Ajicure ADH
Adipic acid dihydrazide
Technicure ADH
Epicure PD 797
