Characteristics and Uses of Melamine Resin

Summary Note

Melamine resin is used as a curing agent for polyol resins in one-part heat-curing paints. It blends well with other resins and is cost-effective.

What is Melamine Resin? 

Melamine resin is a type of amino resin, primarily produced by combining formaldehyde and various alcohols. This resin is commonly used in paint applications and exists in two main forms: fully alkylated melamine monomers and partially alkylated melamine resin. Methyl alcohol and butyl alcohol are often used as alcohols, resulting in methylated melamine and butylated melamine, respectively. 

2. Features

Melamine resin, when heated in an acidic environment with polyol resins containing hydroxyl groups, forms a cross-linked structure through alcohol elimination and dehydration reactions. This cross-linking involves self-condensation reactions and can lead to the generation of formaldehyde. Melamine resin has a high functional group concentration and excellent compatibility with other resins. 

3. Usage 

Melamine resin is typically used in one-part heat-curing paint by mixing it with acrylic polyol resins or polyester polyol resins. The usual mixing ratio with polyol is in the range of 8:2 to 6:4 (polyol: melamine) by solid content, and it’s heated to cure within a temperature range of 100 to 180°C. Since the cross-linking reaction occurs under acidic conditions, catalysts like p-toluenesulfonic acid are added, or acidic polyol resins are used. For water-based paints, methylated melamine is suitable, and a mixture of methyl/butyl alkylated melamine resin is used in water-dispersible paints. 

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