What Is THPA?

Tetrahydrophthalic anhydride (THPA) is a cycloaliphatic anhydride produced by the Diels–Alder reaction of maleic anhydride with butadiene. It is supplied as white flakes with a melting point of 100–102 °C, giving it excellent storage and transport stability — in contrast to liquid methyl anhydrides such as MTHPA and MHHPA.

THPA is one of those versatile molecules that plays two distinct roles in the resins industry. As an epoxy curing agent, it delivers reliable anhydride cure chemistry with good electrical and mechanical properties in the cured system. As a resin-building raw material, it is a standard component in unsaturated polyester resins (UPR) and alkyd resins, where it measurably improves air-drying performance — especially valuable in high-grade resin putties and air-drying coatings.

Beyond resins, THPA serves as a chemical intermediate for plasticisers, insecticides, vulcanising regulators, surfactants and certain printing-ink formulations, with good solubility in acetone, benzene and most general organic solvents.

Key Performance Benefits

Applications & Uses

Unsaturated Polyester & Alkyd Resins

THPA is a primary raw material for unsaturated polyester resins and alkyd resins, where it improves air-drying performance. It is especially suited to high-grade resin putties and air-drying coatings, where faster tack-free times and clean through-drying directly improve production output and finish quality.

Epoxy Resin Curing Agent

As an anhydride hardener, THPA is widely applied in epoxy resin systems for casting, potting and laminating applications. Its high purity and low maleic anhydride residue support predictable gel times and reliable cured properties. For fully liquid epoxy lines, see our liquid alternatives MTHPA and MHHPA.

Coatings, Adhesives & Inks

THPA is used in coatings, adhesives and printing-ink formulations, contributing fast-drying film formation and good adhesion characteristics in solventborne systems.

Chemical Intermediates

As a versatile building block, THPA is used to produce plasticisers, insecticides, vulcanising regulators and surfactants, where its anhydride functionality and residual double bond enable further derivatization.

Technical Specifications

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

Processing & Handling Guidance

Unlike liquid methyl anhydrides, THPA must be converted to a workable form before blending:

• Melt processing — melt THPA in a heated vessel at 105–120 °C, then meter into the resin system; keep transfer lines heated to prevent re-solidification
• Solvent dissolution — dissolve in acetone, benzene, toluene or another compatible solvent for liquid formulations and coating systems
• Epoxy use — for anhydride-cured epoxy, combine molten THPA with liquid epoxy resin and a tertiary-amine accelerator (typically 0.5–2 phr); validate cure schedules in your own system
• Moisture control — keep containers sealed until point of use; anhydride content declines with exposure to humid air

THPA vs. Other Anhydride Curing Agents

Choosing the right anhydride depends on physical form, cost and end-use requirements. This comparison reflects typical industry characteristics:

Not sure which anhydride fits your process? Contact our technical team — we review resin type, processing form and cure-line parameters before recommending a hardener.

Quality Assurance & Documentation

Every THPA 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

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

Safety, Handling & Storage

THPA 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 of dust or vapors
• PPE: chemical-resistant gloves, safety goggles, dust protection and adequate ventilation are required during handling
• Moisture sensitivity: keep bags tightly sealed; anhydride content declines with exposure to humid air
• Storage: cool, dry, well-ventilated area away from heat, ignition sources and oxidizers
• Hot-melt precautions: when melting THPA, control temperature and ventilation — avoid overheating above 150 °C
• Spill response: sweep up solids with dust control, contain with inert absorbent and dispose per local regulations — never flush to drains

Frequently Asked Questions

THPA has two main roles: raw material for unsaturated polyester resins and alkyd resins (improved air-drying performance, especially in high-grade resin putties and air-drying coatings), and curing agent for epoxy resin systems. It also serves as an intermediate for plasticisers, insecticides, vulcanising regulators, surfactants and printing inks.

THPA is the unmethylated parent anhydride — a solid (white flakes, MP 100–102 °C) that must be melted or dissolved before use, with purity ≥ 99.0%. MTHPA is its methylated derivative — liquid at room temperature, easier to meter and mix, preferred for liquid epoxy casting and potting. THPA is the standard choice for UPR and alkyd resin synthesis.

Melt it in a heated vessel at 105–120 °C, or dissolve it in a compatible solvent (acetone, benzene and most organic solvents). Keep transfer lines heated to prevent re-solidification during processing.

THPA introduces controlled residual unsaturation and anhydride functionality into the resin backbone, accelerating oxidative drying and hardening — shorter tack-free times and better through-drying in air-drying coatings and putties.

In tightly closed original packaging, in a cool, dry, well-ventilated place, protected from moisture and heat. Keep bags sealed until point of use — anhydrides react with atmospheric humidity over time.

25 kg kraft paper bags (approx. 20 MT per 20-ft container), 500 kg jumbo bags (approx. 15 MT per 20-ft container) and bulk loading (approx. 28 MT per 40-ft container). Trial quantities can be arranged.

Yes — complete documentation is provided with every shipment and available on request before ordering.

Why Source THPA 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 product line serves high-end new material fields such as wind power, photovoltaics, rail transit, LED and new energy vehicles.

Related Products & Resources

• Methyltetrahydrophthalic Anhydride (MTHPA) — liquid hardener for general electrical insulation and composites
• Methylhexahydrophthalic Anhydride (MHHPA) — high-purity liquid hardener for LED encapsulation and color-critical systems
• All anhydride curing agents
• Anhydride curing agent selection guide — solid vs. liquid trade-offs explained
• THPA Technical Data Sheet (TDS)