High-Purity Solvents, Polyurethane (PU) and Resin

Methyl Hexahydrophthalic Anhydride (MHHPA)

Methyl Hexahydrophthalic Anhydride (MHHPA), identified by CAS number 25550-51-0, is a high-purity cycloaliphatic dicarboxylic acid anhydride primarily utilized as a curing agent for epoxy resins. It is produced through the catalytic hydrogenation of methyl tetrahydrophthalic anhydride (MTHPA). Structurally, it consists of a saturated six-membered ring with a fused anhydride functional group and a methyl substituent. Unlike its precursor or other aromatic anhydrides, MHHPA is a liquid at room temperature, which significantly simplifies handling, mixing, and processing in industrial environments.

As a high-performance hardener, MHHPA is favored for applications requiring exceptional optical clarity, low color, and superior resistance to ultraviolet (UV) radiation and weathering. It provides cured epoxy systems with excellent mechanical strength, high heat distortion temperatures, and outstanding electrical insulation properties. Because it is a saturated cyclic compound, it exhibits better oxidative stability than unsaturated or aromatic counterparts, making it a critical component in high-voltage electrical insulation and outdoor electronic encapsulation.

Attributes

Key Features and Benefits

Low Viscosity: Its liquid state and low viscosity allow for excellent pourability and high filler loading, reducing overall formulation costs.
High Clarity: Produces highly transparent cured products with minimal initial color, essential for optical and LED applications.
Superior Weatherability: Exceptional resistance to UV degradation and yellowing compared to aromatic curing agents like Phthalic Anhydride (PA).
Excellent Electrical Insulation: Offers high dielectric strength and low dielectric loss, maintaining performance under high-voltage stress.
Extended Pot Life: Provides a long working window at room temperature when mixed with epoxy resins, facilitating large-scale manufacturing.
Thermal Stability: Delivers high glass transition temperatures (Tg) and chemical resistance in cured matrices.

Specifications

Technical Highlights

Chemical Formula: C₉H₁₂O₃ (Molecular Weight: ~168.19 g/mol).
Physical State: Colorless, transparent liquid with low volatility.
Anhydride Content: Typically ≥ 42.0% (Purity ≥ 98%).
Viscosity: Ranges between 40–80 mPa·s at 25°C, ensuring ease of impregnation.
Free Acid Content: Low acidity (≤ 1.0%) to ensure stability and consistent reactivity.
Curing Profile: Requires an accelerator (e.g., tertiary amines, imidazoles, or metal carboxylates) for efficient cross-linking at elevated temperatures (100°C–150°C).
Safety Note: Classified as a respiratory and skin sensitizer; appropriate PPE and ventilation are required during handling.

Download Technical Data Sheet (TDS)

Practical industry uses

Applications

Electrical Insulation: Used in casting high-voltage transformers, dry-type transformers, insulators, and capacitors.
Electronic Encapsulation: Ideal for LED potting, semiconductor packaging, and printed circuit board (PCB) coatings due to its optical clarity.
Advanced Composites: Utilized in filament winding and pultrusion processes for manufacturing high-strength pipes, tanks, and structural automotive components.
High-Performance Coatings: Formulated into weather-resistant powder coatings and solvent-borne industrial finishes requiring chemical durability.
Adhesives: Component in structural epoxy adhesives for aerospace and automotive assembly where thermal cycling resistance is mandatory.
Sports Equipment: Used in carbon-fiber-reinforced polymers for high-end bicycles, rackets, and marine applications.