Methylhexahydrophthalic Anhydride (MHHPA)
A high-purity, colorless liquid cycloaliphatic anhydride hardener that delivers excellent color retention, heat resistance and electrical insulation in epoxy casting, potting, encapsulation, lamination, adhesive and pultrusion systems.
Product Identification at a Glance
What Is MHHPA?
Methylhexahydrophthalic anhydride (MHHPA) is a high-purity cycloaliphatic anhydride used primarily as a curing agent for epoxy resin systems. It is produced by the complete hydrogenation of methyltetrahydrophthalic anhydride (MTHPA): the residual double bond in the MTHPA ring is saturated, yielding a stable, colorless liquid at room temperature.
This saturated ring structure is what sets MHHPA apart. Because there are no residual unsaturations to oxidize or discolor under heat and UV exposure, MHHPA-cured epoxy systems achieve outstanding color retention and weathering stability — the reason it is the hardener of choice for LED encapsulation, optical components and light-colored or outdoor products.
Its low viscosity supports easy handling, good resin wetting and high filler loading, while helping cured systems deliver good heat resistance, electrical insulation, moisture resistance, mechanical performance and color retention in a single formulation.
Key Performance Benefits
Ultra-Low Colour (Hazen ≤ 20)
Colourless transparent liquid with the lowest color rating in the methyl anhydride family — essential for transparent and light-colored cured parts.
UV & Weathering Stability
Fully saturated ring structure resists yellowing under heat and UV exposure, protecting light output and appearance over service life.
High Purity (≥ 97.0%)
High MHHPA content with low free acid supports consistent, reproducible cure behavior and reliable electrical properties.
Low Viscosity, High Filler Loading
45–75 mPa·s at 25 °C enables good resin wetting and high mineral-filler loading for cost-optimized, low-CTE formulations.
Excellent Electrical Insulation
Strong dielectric performance for transformers, capacitors, ignition coils and switchgear in long-term service.
Heat & Moisture Resistance
Cured systems combine thermal stability with low moisture uptake for demanding indoor and outdoor electrical assemblies.
Applications & Uses
LED & Optical Encapsulation
With colorless transparency and superior UV/thermal yellowing resistance, MHHPA-cured epoxy is widely used for LED encapsulation, optical lenses and transparent potting, where discoloration directly reduces light output. MHHPA is the hydrogenated upgrade path from MTHPA for these color-critical applications.
Electrical & Electronic Insulation
MHHPA is used in epoxy casting, potting and encapsulation for electrical and electronic components, including transformers, capacitors, ignition coils, switchgear and other insulation assemblies. Low viscosity and high purity support vacuum casting and impregnation with high electrical yield rates.
Adhesives, Coatings & Composites
MHHPA is also suitable for epoxy adhesives, coatings, laminates, filament-wound parts and epoxy-matrix composites where low viscosity, heat resistance and durable mechanical properties are required.
Core Processing Methods
- Casting & potting — encapsulating electronic modules, sensors and insulators
- Electrical encapsulation & impregnation — sealing windings, coils and assemblies
- Lamination & epoxy-matrix composites — insulation sheets and structural parts
- Adhesives, coatings & pultrusion — surface and structural applications
Technical Specifications
| Property | Specification |
|---|---|
| Appearance | Colourless transparent liquid |
| MHHPA content | ≥ 97.0% |
| Colour (Hazen) | ≤ 20# |
| Viscosity (25 °C) | 45.0–75.0 mPa·s |
| Acid value | ≥ 650 mg KOH/g |
| Freezing point | ≤ −15 °C |
| Free acid | ≤ 1.0% |
Each production batch is released against this specification and documented in the Certificate of Analysis (COA). Full test methods are described in the TDS, available on request.
Physical & Chemical Properties
| Property | Value |
|---|---|
| Physical state (25 °C) | Liquid |
| CAS number | 25550-51-0 |
| Molecular formula | C₉H₁₂O₃ |
| Molecular weight | 168.19 g/mol |
| Density (20 °C) | 1.18 ± 0.05 g/cm³ |
Formulation & Curing Guidance
MHHPA is typically used with standard liquid bisphenol-A epoxy resins (EEW 185–195 g/eq). The information below is a typical starting point — always validate in your own system before production.
| Parameter | Typical Range |
|---|---|
| Recommended MHHPA loading | 80–100 phr (based on 100 parts epoxy resin; adjust to resin EEW and target properties) |
| Accelerator (BDMA, 2,4-EMI) | 0.5–2 phr tertiary amine |
| Pot life (mixed, 25 °C) | Hours — depends on accelerator level and ambient temperature |
| Typical cure schedule | Gel / pre-cure at 80–100 °C, post-cure at 120–150 °C to reach full properties |
MHHPA vs. Other Anhydride Curing Agents
Choosing the right anhydride depends on cost, color stability and end-use requirements. This comparison reflects typical industry characteristics:
| Property | MHHPA | MTHPA | THPA | Phthalic Anhydride (PA) |
|---|---|---|---|---|
| Physical state (25 °C) | Liquid | Liquid | Solid (flakes) | Solid |
| Ring structure | Saturated (hydrogenated) | One double bond | One double bond | Aromatic |
| Colour / yellowing resistance | Excellent (Hazen ≤ 20) | Good | Fair | Fair |
| Electrical insulation | Excellent | Excellent | Good | Good |
| Relative cost | Medium–high | Low–medium | Low | Low |
| Typical use | LED encapsulation, optical parts, outdoor/light-colored products | General electrical insulation, casting, composites | Economy solid systems | Cost-driven solid systems |
Not sure whether MHHPA or MTHPA fits your application? Contact our technical team — we review resin, filler and cure-line parameters before recommending a hardener.
Quality Assurance & Documentation
Every MHHPA order ships with a complete documentation package. Batch traceability is maintained from production to container loading.
- TDS (Technical Data Sheet) — specifications, test methods and handling guidance
- COA (Certificate of Analysis) — actual batch test results against specification
- MSDS / SDS — safety, transport and regulatory information
- Container loading report — photographic and weight documentation of every shipment
- ISO 9001-aligned quality management — [confirm and display your actual certification]
- REACH / regulatory support — [confirm your registration or pre-registration status for the EU market]
Packaging Options
| Package Type | Packing Detail | Net Weight per 20′ FCL |
|---|---|---|
| IBC container | 1,000 kg per IBC | Approx. 18 metric tons |
| Isotank | Available on request | Approx. 25 metric tons |
| Steel drum | 220 kg per drum, palletized | Approx. 17.6 / 19.2 metric tons |
Custom packaging and small trial quantities for formulation development can be arranged — ask our sales team for details.
Shipping & Commercial Terms
FOB Ningbo
- Goods delivered to the port of departure
- Target readiness: 10 days after order confirmation
- Payment: 30% deposit, 70% before shipment
- Container loading report provided
- Dedicated client manager for your account
CIF Basis
- Goods delivered to your destination port, with international logistics arranged by us
- Route and freight-rate planning for cost-optimized shipments
- Coordination with major shipping lines, including Maersk, ONE, KMTC and CMA CGM
- Purchase insurance and related fees handled by the supplier
- Container loading report provided
- Dedicated client manager for your account
General Conditions
| Item | Terms |
|---|---|
| Payment | Negotiable for long-term partners |
| Documentation | Purchase-related documents can include TDS, MSDS, COA and other required paperwork |
Safety, Handling & Storage
MHHPA is a reactive chemical and must be handled with appropriate industrial precautions. Always consult the current MSDS before use.
- Corrosive / sensitizer: anhydrides can cause skin burns and respiratory sensitization — avoid all contact and inhalation
- PPE: chemical-resistant gloves, safety goggles and adequate ventilation are required during handling
- Moisture sensitivity: keep containers tightly sealed; anhydride content declines with exposure to humid air
- Storage: cool, dry, well-ventilated area away from heat, ignition sources and oxidizers; recommended storage at 5–35 °C
- Spill response: contain with inert absorbent and dispose per local regulations — never flush to drains
Frequently Asked Questions
What is MHHPA used for?MHHPA is a high-purity cycloaliphatic anhydride used primarily as a curing agent for epoxy resin systems — LED encapsulation and optical potting, electrical and electronic encapsulation (transformers, capacitors, ignition coils, switchgear), plus adhesives, coatings, laminates, filament-wound parts and epoxy-matrix composites.
What is the difference between MHHPA and MTHPA?MHHPA is the fully hydrogenated version of MTHPA. Its saturated ring gives superior color stability and UV/weathering resistance — ideal for LEDs, optics and light-colored or outdoor products. MTHPA retains one double bond, is more economical, and suits general electrical insulation and composites.
Why is color stability important in an epoxy curing agent?In LED encapsulation, optical lenses and transparent potting, discoloration of the cured epoxy directly reduces light output and changes appearance. MHHPA has no residual double bonds, so cured systems keep colorless transparency and resist yellowing under heat and UV.
What accelerator should be used with MHHPA?Commonly tertiary amines such as BDMA or 2,4-EMI at 0.5–2 phr. Accelerator level controls gel time and pot life; lower levels suit thick sections and vacuum casting.
How should MHHPA be stored?In tightly closed original containers, in a cool, dry, well-ventilated place, at approximately 5–35 °C, protected from moisture and heat. Keep sealed — anhydrides react with atmospheric humidity over time.
What packaging options are available?220 kg steel drums (approx. 17.6–19.2 MT per palletized 20-ft container), 1,000 kg IBC containers (approx. 18 MT per container) and isotanks (approx. 25 MT, available on request). Trial quantities can be arranged.
Do you provide MSDS, COA and TDS documents?Yes — complete documentation is provided with every shipment and available on request before ordering.
Why Source MHHPA From Heyi Chemical
Zhejiang Heyi Chemical Co., Ltd. is a new materials company integrating R&D, production and sales, located in the Modern Pharmaceutical and Chemical Park of Xianju Economic Development Zone, Zhejiang Province. Established in March 2022 with production starting in June 2024, our approximately 64,000 m² facility features inherently safe engineering design and intelligent management and control. Our anhydride curing agents serve high-end new material fields such as LED, wind power, photovoltaics, rail transit and new energy vehicles.
Dedicated Anhydride Production Base
64,000 m² purpose-built facility in Xianju, Zhejiang — built for consistent high-purity quality, close to Ningbo port.
New Capacity, Modern Design
Plant constructed from 2023 with inherently safe engineering and intelligent process control throughout.
Technical Support
Formulation and cure-schedule guidance from our R&D team, with typical response within 24 hours on business days.
Export Experience
Clear FOB/CIF structures, coordination with Maersk, ONE, KMTC and CMA CGM, and a dedicated client manager per account.
Technical Review
This page has been reviewed by the Heyi Chemical technical team. Questions about specifications or applications? Email our technical desk — typical response within 24 hours on business days.
Related Products & Resources
- Methyltetrahydrophthalic Anhydride (MTHPA) — economical liquid hardener for general electrical insulation and composites
- All anhydride curing agents
- MTHPA vs. MHHPA: how to choose — color stability vs. cost trade-off explained
- MHHPA Technical Data Sheet (TDS)
Request a Quote for MHHPA
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