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Hydroxyalkylamide (HAA) Resin, also known as β-Hydroxyalkylamide, is an environmentally friendly curing agent widely used in polyester powder coatings.
Hydroxyalkylamide (HAA) Resin serves as a formaldehyde-free alternative to TGIC, offering smooth appearance, stable gloss, and excellent mechanical balance.
Hydroxyalkylamide (HAA) Resin plays a crucial role in indoor powder coatings and selected outdoor systems where environmental compliance and low-temperature curing are important.
CAS: 6334-25-4
MF: C14H28N2O6
MW: 320.38
EINECS: 405-370-0
Chemical Formula: C14H28N2O6
Synonyms: N,N,N',N'-Tetrakis(2-hydroxyethyl)-hexanediamide,Hexanediamide, N,N,N,N-tetrakis(2-hydroxyethyl)-,ACETOMER 552,N,N,N'',N''-TETRAKIS(2-BYDROXYETHYL)ADIPAMIDE,N,N,N′,N′-Tetrakis-(2-hydroxethyladipamid),Beta-Hydroxyalkylamide,N,N,N',N'-Tetrakis(2;N,N,N',N'-tetrakis(2-hydroxyethyl)adipmide
Hydroxyalkylamide (HAA) Resin is a cross-linking and curing agent primarily used with carboxyl-terminated polyester resins in powder coatings.
Hydroxyalkylamide (HAA) Resin serves as a safer, highly durable, and environmentally friendly alternative to traditional TGIC (Triglycidyl Isocyanurate) hardeners.
Hydroxyalkylamide (HAA) Resin polyester resin is a polymer material used to form chemical bonds.
Hydroxyalkylamide (HAA) Resin is used in applications such as coating and composite material production in various industries.
Hydroxyalkylamide (HAA) is not a base resin itself, but rather an environmentally friendly, non-toxic curing agent (or hardener) used alongside polyester or acrylic resins.
Together, they form HAA powder coatings, which are renowned for their exceptional outdoor durability, mechanical strength, and UV resistance.
Hydroxyalkylamide (HAA) Resin, scientifically referred to as β-Hydroxyalkylamide, is a highly important, non-toxic crosslinking agent (hardener) extensively utilized in the thermosetting powder coating industry.
Hydroxyalkylamide (HAA) Resin serves as the main "TGIC-free" alternative for curing outdoor-durable, carboxyl-terminated polyester and acrylic resins.
Coatings using these resins form a durable and protective layer.
Hydroxyalkylamide (HAA) Resin provide resistance to abrasion, scratching, chemical effects and UV rays.
Therefore, they are preferred in the automotive industry, metal coatings, wood coatings and many other industrial coating applications.
Hydroxyalkylamide (HAA) Resin is a kind of amide compound containing 2-4 hydroxyl functional groups.
Because its hydroxyl group is in the β position, Hydroxyalkylamide (HAA) Resin is affected by N atoms and has high activity.
Hydroxyalkylamide (HAA) Resin can be used as a chemical intermediate and a cross-linking agent for carboxyl polyester resin and polyacrylic resin.
Unlike TGIC, which contains epoxy groups, Hydroxyalkylamide (HAA) reacts with carboxyl-functional polyester Resins through a β-hydroxyalkylamide reaction mechanism.
This produces a durable, crosslinked coating without releasing harmful by-products.
Because of its safe handling profile, Hydroxyalkylamide (HAA) is often chosen in regions with strict environmental regulations.
For PCOTEC, Hydroxyalkylamide (HAA) Resin Curing Agents such as TK-H220 and TK-H320 support a wide range of indoor and semi-outdoor applications where appearance and sustainability are key requirements.
HAA curing agents are synthesized from aliphatic compounds containing hydroxyl and amide groups.
These reactive groups enable crosslinking with polyester resin during curing.
Common Applications
Because HAA creates a tough, protective finish that withstands harsh weather and sunlight, Hydroxyalkylamide (HAA) Resin is widely utilized across several industries for finishing and protecting metal:
Architectural elements: Fencing, railings, and aluminum window frames.Automotive: Wheels, trim, and exterior components.
Outdoor furniture: Lawn chairs, patio sets, and playground equipment.
General industrial: Agricultural machinery and electrical enclosures.
What HAA Is Made Of
HAA curing agents are synthesized from aliphatic compounds containing hydroxyl and amide groups.
These reactive groups enable crosslinking with polyester resin during curing.
Main structural features include:
Hydroxy functional groups
Amide groups
Aliphatic backbone
Low volatility molecular design
This composition allows HAA to cure without emitting formaldehyde and produces coatings with smooth, uniform finishes.
How Hydroxyalkylamide (HAA) Resin Works in Powder Coatings
When Hydroxyalkylamide (HAA) Resin powder coatings enter the curing oven, the curing agent begins reacting with the resin’s carboxyl groups.
The process forms a crosslinked 3D network that determines hardness, gloss, and durability.
Crosslinking process:
Melting – Resin and HAA blend uniformly.
Reaction – Hydroxyl and amide groups react with carboxyl groups.
Network formation – A stable polymer structure develops.
Solidification – The coating cools into a smooth, durable film.
This reaction mechanism produces lower-temperature curing capability than many traditional systems.
Why Hydroxyalkylamide (HAA) Resin is Used
Hydroxyalkylamide (HAA) Resin emerged in the 1990s primarily as a safe, eco-friendly alternative to traditional hardeners like TGIC (triglycidyl isocyanurate), which were restricted due to health concerns.
Key advantages of HAA include:Eco-Friendly: Hydroxyalkylamide (HAA) Resin is completely free of formaldehyde and toxic mutagens.
Low-Temperature Curing: HAA-based systems can cure at lower temperatures (around 180°C) than TGIC, saving energy and processing time.
Mechanical Excellence: Hydroxyalkylamide (HAA) Resin creates a dense, highly crosslinked structure that provides excellent impact resistance and flexibility.
Key Characteristics
Function: Acts as a hardener/crosslinker for powder coatings to create a tight, 3D polymer network.
Curing Mechanism: Reacts with carboxyl groups in polyester resins via a poly-condensation reaction, releasing water as the only volatile by-product (H₂O).
Safety & Health: Unlike TGIC, HAA-based systems are generally classified as non-toxic and non-mutagenic, making them significantly safer to handle during manufacturing.
Curing Temperature: Standard Hydroxyalkylamide (HAA) Resin formulations cure at temperatures around 160°C to 200°C, though highly reactive polyesters allow for reduced curing temperatures down to 150°C.
Performance Benefits
Weathering & UV Resistance: Offers excellent exterior durability, making Hydroxyalkylamide (HAA) ideal for architectural metals.
Mechanical Properties: Delivers exceptional film flexibility, impact resistance, and scratch resistance.
Chemical Resistance: Protects surfaces against solvents, abrasions, and chemical exposure.
Key Features and Advantages
Eco-Friendly & Safe (Hazard-Free): The primary driver for adopting Hydroxyalkylamide (HAA) Resin is its exceptional toxicological profile.
While TGIC is classified as a Category 2 mutagen and reproductive toxicant requiring strict labeling, HAA is completely non-toxic, non-irritant, and requires no hazardous hazard-labeling under GHS/CLP regulations.
Excellent Weathering and UV Resistance: HAA-cured polyester systems provide outstanding gloss retention and chalking resistance, meeting architectural standards like Qualicoat and GSB in Europe.
High Transfer Efficiency: Hydroxyalkylamide (HAA) Resin exhibits excellent electrostatic charging characteristics (high tribo-charging acceptance), resulting in an outstanding first-pass transfer efficiency during powder gun spraying.
Overbake Yellowing Resistance: Hydroxyalkylamide (HAA) Resin demonstrates great thermal stability, offering excellent resistance to color shifts or browning if the parts are accidentally exposed to overbake conditions or high temperature curing.
Application and Processing Limitations
Despite its safety benefits, HAA formulations require precise R&D adjustments due to the nature of the condensation reaction:
Pinholes and Blistering (The Blister Limit): Since water vapor is released during curing, if the coating layer is applied too thick, the trapped moisture cannot escape before the film gels. This causes micro-defects like pinholes or popping.
Degassing Agents Required: To fight the water entrapment, a degassing additive like Benzoin is mandatory in HAA systems to keep the molten film open long enough for water vapor to safely escape.
Hygroscopic Nature: HAA powder hardeners are sensitive to ambient moisture and humidity.
Raw materials and finished powders must be stored in cool, dry environments to prevent caking and fluidization issues.
Lack of Catalysts: Unlike TGIC, whose curing temperature can be sped up or lowered using catalysts, effective chemical accelerators for the HAA-carboxyl reaction are virtually non-existent. Curing is strictly dependent on temperature profiles (typically 180°C for 15 mins or 200°C for 10 mins).
Primary Applications
Architectural & Metal Coatings: Used for outdoor fixtures, fencing, and aluminum extrusions.
Automotive: Applied for protective underbody and wheel coatings.
Wood & Appliance Coatings: Protects sensitive substrates requiring smooth, robust finishes.
Key Features of HAA Curing Agents
HAA offers several benefits in powder coatings, especially where appearance and environmental compliance matter.
Main features:
Formaldehyde-free curing
Smooth film appearance
Consistent gloss stability
Good mechanical flexibility
Low-temperature curing capability
Safe handling and eco-friendly profile
These characteristics make Hydroxyalkylamide (HAA) Resin popular in regions prioritizing environmental standards and low emission materials.
Chemical Properties
Melting point : 126.0 to 130.0 °C
Boiling point : 607.7±55.0 °C(Predicted)
density : 1.239
vapor pressure : 0-0.002Pa at 20-25℃
storage temp. : Inert atmosphere,Room Temperature
form : powder to crystal
pka: 13.82±0.10(Predicted)
color: White to Light yellow
Water Solubility : 600-625g/L at 20℃
InChI: InChI=1S/C14H28N2O6/c17-9-5-15(6-10-18)13(21)3-1-2-4-14(22)16(7-11-19)8-12-20/h17-20H,1-12H2
InChIKey: OKRNLSUTBJUVKA-UHFFFAOYSA-N
