Maleic anhydride

Maleic anhydride (CAS 108-31-6), also known as MA, is a high-volume reactive monomer and chemical intermediate used in polymer, resin, and specialty chemical manufacturing.

Where is Maleic anhydride used?

• Unsaturated polyester resins: core monomer for laminates, gel coats, and fiber-reinforced composites in construction and automotive parts
• Plastics and polymer processing: grafted onto polyolefins such as polyethylene and polypropylene to improve adhesion, compatibility, and surface wettability
• Textile and paper treatment: derived copolymers as sizing agents and surface modifiers for fiber bonding and coating adhesion
• Personal care: MA-based copolymers as film-forming and fixative agents in hair care
• It also serves as a building block for maleic acid derivatives and copolymers.
• Reactive coatings such as alkyds: introduces polymerization sites for crosslinking.
• UV-cured coatings: provides a reactive site.
• Alkenyl succinic anhydrides (ASA) for paper sizing, detergents, oilfield chemicals, and epoxy curing agents: necessary for their preparation.

Formulation notes

• A typical unsaturated polyester resin formulation contains 30-40% maleic anhydride.
• In the presence of strong bases such as sodium hydroxide, potassium hydroxide, or calcium hydroxide at temperatures above 150°C, violent exothermic decomposition occurs with production of carbon dioxide.
• With 0.1% pyridine at 185°C, exothermic decomposition occurs with rapid evolution of gas.
• Reacts exothermically with water or steam.

Typical specification

• Colour (APHA, molten) ≤10.

Regulatory status

• Carries hazard statement H302, harmful if swallowed.
• For transport, classified as UN Class 8 (corrosive) with UN packing group III.
• The harmonised EU CLP Index Number is 607-096-00-9.
• The MAK occupational exposure limit is 0.081 mg/m³ (0.02 ppm) with peak limitation category I(1), respiratory and skin sensitisation (SAH), and pregnancy risk group C.

Storage, packaging and handling

• Should be stored fireproof, only in its original packaging, separated from strong oxidants, strong reducing agents and incompatible materials, dry, and in an area without drains or sewer access.

Frequently asked questions about Maleic anhydride

What is the specific concentration limit for skin sensitisation?

A specific concentration limit of ≥0.001% applies for skin sensitisation category 1A (H317).

How does maleic anhydride affect the properties of a formulation?

Maleic anhydride increases the glass transition temperature to improve hardness and shorten drying times.

Technical content is compiled and updated by the SoleChem product team from public technical sources; the certificate of analysis (COA) governs product-specific specifications.