Why is MTHPA (CAS 11070-44-3) preferred over standard Amine hardeners for electrical potting?

Exotherm control and properties. Amine hardeners cure quickly at room temperature but generate significant heat (exotherm), which can crack large castings. MTHPA cures slowly and requires heat, allowing for a controlled, low-exotherm reaction that is safe for large, thick parts. Furthermore, MTHPA-cured epoxies possess significantly better electrical insulation and thermal stability (Class F/H insulation) compared to amine-cured systems.

Does this curing agent require an accelerator?

Yes. MTHPA reacts very slowly with epoxy resin on its own. To achieve practical curing times at elevated temperatures (typically 100°C - 150°C), a tertiary amine accelerator (such as DMP-30 or BDMA) is almost always added to the formulation, typically at 0.5% to 2.0% of the resin weight.

Methyltetrahydrophthalic Anhydride (MTHPA) CAS 11070-44-3

Methyltetrahydrophthalic Anhydride (MTHPA) CAS 11070-44-3 is a high-performance liquid anhydride hardener chemically defined as a mixture of methylated tetrahydrophthalic isomers , functioning primarily as a curing agent for epoxy resins in electrical casting and composite manufacturing. Distinguished by its low viscosity at room temperature, light color, and long pot life, this curing agent is extensively utilized in the production of fiberglass reinforced plastics (FRP) pipes, wind turbine blades, and high-voltage electrical insulators (casting/potting). Unlike amine hardeners, MTHPA requires heat to cure but results in a polymer matrix with superior heat deflection temperature (HDT), excellent electrical insulation properties, and minimal shrinkage. We provide professional access to this material with competitive factory pricing and the ability to meet customized specifications (varying anhydride equivalent weights) for various manufacturing requirements. Our commitment to technical transparency ensures that every shipment is accompanied by comprehensive MSDS, TDS, COA documentation to support your quality assurance protocols, and we maintain capacity for consistent bulk supply to facilitate large-scale industrial operations.

CAS: 11070-44-3
Synonyms: MTHPA, Methyl tetrahydrophthalic anhydride, 4-Methyl-1,2,3,6-tetrahydrophthalic anhydride, Epoxy Anhydride Hardener, Liquid Anhydride Curing Agent
Einecs: 234-290-7
Molecular Formula: C9H10O3
Grade: Electronic Grade, Electrical Potting Grade.
Package: 220kg Iron Drum or 1200kg IBC Tank.

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Product Description

Methyl Tetrahydrophthalic Anhydride (MTHPA) is a high-performance, liquid alicyclic anhydride curing agent. It is widely preferred in the composite and electrical insulation industries due to its low viscosity at room temperature, low volatility, and long pot life. Unlike solid curing agents, MTHPA allows for easier handling and superior impregnation of complex components.

Our MTHPA series is synthesized via isomerization technology to ensure a stable structure. When cured with epoxy resins, it imparts excellent electrical properties, high heat resistance (high Tg), and superior mechanical strength to the final product. It is the gold standard hardener for casting, potting, and encapsulation applications.

Need technical advice on mixing ratios or accelerators? 📧 Email: info@industrochem.com

We offer customizable isomer ratios to fine-tune the freezing point and viscosity to match your specific climate and production environment.

1 Physicochemical Properties (Technical Data)

2 Applications

3 Quality Assurance (QA/QC)

4 Storage, Handling & Safety

Physicochemical Properties (Technical Data)

The following specifications represent our Standard Electronic Grade, typically used for high-voltage insulation and LED packaging.

Property	Specification
Appearance	Pale yellow transparent liquid
Purity (by GC)	≥99.0%
Anhydride Content	≥41.0%−42.0%
Viscosity (25°C)	20 – 50 mPa.s
Color (APHA/Pt-Co)	≤100
Freezing Point	≤−15S℃
Volatile Content	≤1.0%
Free Acid	≤1.0%
Specific Gravity (25°C)	1.20 – 1.22 g/cm³
Gel Time (with accelerator)	Customizable (e.g., >200 min at 100°C)

Applications

MTHPA is the critical hardener for applications requiring durability and electrical insulation:

1. Electrical Encapsulation & Potting:

Transformers & Coils: Used extensively for the impregnation and casting of ignition coils, high-voltage transformers, and mutual inductors due to its excellent dielectric properties.
Capacitors: Provides a hermetic seal that protects internal components from moisture and vibration.

2. Electronic Components:

LED Packaging: Its low color (APHA) and resistance to yellowing make it ideal for clear LED potting compounds.
PCBs: Used in insulating varnishes for printed circuit boards.

3. Composite Materials:

Wind Energy: Used in the vacuum infusion process for manufacturing wind turbine blades.
FRP Piping: Acts as a curing agent for filament-wound fiberglass pipes requiring chemical resistance.

4. Industrial Adhesives:

Formulates into high-strength structural adhesives for metal and ceramic bonding.

Quality Assurance (QA/QC)

At Industrochem, we ensure that every drop of MTHPA meets the stringent requirements of the electronics industry.

Isomer Control: We use advanced Gas Chromatography (GC) to monitor the distribution of isomers (3-methyl and 4-methyl), which directly impacts the viscosity and freezing point of the product.
Moisture Management: As anhydrides are sensitive to moisture (hydrolysis), our production lines are fully enclosed nitrogen-sealed systems. We strictly test Free Acid content to ensure no degradation has occurred.
Color Stability: For LED grade products, we perform rigorous UV aging tests and colorimetry to guarantee low yellowing index over time.

Storage, Handling & Safety

Storage Conditions:

Moisture Sensitivity: Critical. MTHPA reacts with atmospheric moisture to form acid. Containers must be kept tightly sealed at all times.
Temperature: Store in a cool, dry place between 5°C and 30°C. Although it has a low freezing point, avoiding extreme cold prevents crystallization.
Shelf Life: 12 months in original sealed packaging.

Safety Precautions (HSE):

Skin & Eye Contact: Anhydrides can be irritating to the skin, eyes, and respiratory system. May cause sensitization.
PPE Recommendations:
- Respiratory: Wear a half-face respirator with organic vapor cartridges if ventilation is poor.
- Skin: Butyl rubber or Neoprene gloves are recommended. Long-sleeved protective clothing is mandatory.
- Eyes: Chemical splash goggles.
Handling: operate in a well-ventilated area. In case of contact with skin, wash immediately with soap and plenty of water.

Optimize your curing process with premium MTHPA.

Whether for high-voltage casting or clear LED potting, our technical team is ready to support your formulation.

👉 Get a Quote: info@industrochem.com

FAQ - Technical & Supply Chain

Q:
Why is MTHPA (CAS 11070-44-3) preferred over standard Amine hardeners for electrical potting?

A: Exotherm control and properties. Amine hardeners cure quickly at room temperature but generate significant heat (exotherm), which can crack large castings. MTHPA cures slowly and requires heat, allowing for a controlled, low-exotherm reaction that is safe for large, thick parts. Furthermore, MTHPA-cured epoxies possess significantly better electrical insulation and thermal stability (Class F/H insulation) compared to amine-cured systems.
Q:
Does this curing agent require an accelerator?

A: Yes. MTHPA reacts very slowly with epoxy resin on its own. To achieve practical curing times at elevated temperatures (typically 100°C - 150°C), a tertiary amine accelerator (such as DMP-30 or BDMA) is almost always added to the formulation, typically at 0.5% to 2.0% of the resin weight.

Documents

Documents and Product Support

For product review and sourcing evaluation, supporting documents can be coordinated according to the product type, inquiry stage, and order requirements.

COA for batch-based quality reference
TDS for key physical and chemical information
SDS / MSDS for handling, storage, and safety reference
Packing information for sample, trial, and bulk orders
Technical communication based on application and specification requirements

Quotation

Information to Confirm Before Quotation

Clear sourcing information helps reduce specification mismatch and allows a more accurate quotation before sample or bulk order discussion.

Product name and CAS number
Application or intended end use
Required purity, grade, or specification
Sample quantity, trial order, or bulk demand
Preferred packing form or net weight
Destination country or port
Required documents or compliance expectations

Storage & Handling

Packaging, Storage, and Handling Notes

Packaging form, storage conditions, shelf life, and shipment arrangements should be confirmed according to the product characteristics, package size, and destination requirements.

Before order confirmation, buyers are advised to review the corresponding product documents and confirm whether any special storage, labeling, or handling requirements apply.

Supply Support

Sample, Bulk Order and Repeat Supply Support

Support can be arranged for sample discussion, bulk supply planning, packaging confirmation, and routine sourcing communication based on the actual product and order requirements.

For repeat-use formulations or long-term procurement plans, buyers may discuss specification consistency, packaging preferences, delivery expectations, and document coordination in advance.

Contact Form

Use our contact form to send us your questions, suggestions or comments. We will respond as soon as possible.

Product Categories

Tags:

Anhydride Curing Agent Epoxy Curing Agent Resin Hardener Unsaturated Anhydride

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