Melamine-Formaldehyde Molding Compound (Melamine Powder)

Melamine-formaldehyde molding compound, commonly referred to as "melamine powder," is a major type of amino-based thermosetting plastic. It is composed of a melamine-formaldehyde resin matrix blended with additives—such as cellulose fillers (typically alpha-cellulose or wood pulp), pigments, lubricants, and curing agents—which are then processed through kneading, drying, and ball milling into a powder or granular form. Melamine powder generally contains approximately 60% melamine-formaldehyde resin, with the remainder consisting primarily of wood pulp cellulose. Compared to urea-formaldehyde molding compounds, melamine powder offers significant advantages in terms of heat resistance, water resistance, and safety for food-contact applications.

Definitions and Grade Classifications

Chemically, melamine powder is a melamine-formaldehyde resin (MF resin), produced through the addition and polycondensation reactions of melamine and formaldehyde, typically in a molar ratio of approximately 1:2 to 1:3. Within industry classification systems, the "A5" grade is the most common food-grade specification for melamine powder. According to patent literature, A5 and A8 grade melamine powders consist of 100% melamine resin and are primarily used for the manufacture of Melamine tableware. In contrast, the "A1" grade belongs to the urea-formaldehyde resin category; while more cost-effective, it is not suitable for food-contact applications. A5-grade material, characterized by its high density and excellent gloss, is well-suited for the production of export-quality tableware.

Physical and Chemical Properties

Products made from melamine powder are non-toxic, odorless, impact-resistant, corrosion-resistant, and capable of withstanding both high and low temperatures. They feature a dense structure and high hardness, making them durable and resistant to breakage. Once cured, the melamine resin is colorless and transparent; it remains stable in boiling water and can even be used at temperatures up to 150°C. Furthermore, it exhibits self-extinguishing properties, arc resistance, and strong mechanical performance. In terms of temperature tolerance, melamine products can withstand a range from -30°C to 120°C. They feature high surface hardness and excellent wear resistance, exhibit good resistance to boiling water, detergents, and weak acids, and are specifically approved for use in food-contact applications. Melamine resin does not cure at room temperature; it typically undergoes thermosetting at 130–150°C, with the addition of a small amount of an acid catalyst serving to accelerate the curing process.

Overview of the Production Process

The production process for melamine molding powder is similar to that of urea-formaldehyde (UF) molding powder, consisting primarily of two main stages: resin synthesis and compounding (kneading). Taking a process disclosed in a patent as an example: formaldehyde solution is first added to a reaction vessel, and the pH is adjusted to approximately 8.5. After adding auxiliaries such as polyvinyl alcohol, the temperature is raised, and melamine is introduced to undergo an addition reaction at 85°C. Once a white precipitate appears in the resin, the temperature is lowered to 75°C; the pH is then adjusted, and polyacrylamide is added to facilitate a polycondensation reaction. Upon completion of the reaction, the mixture is cooled to 70°C and transferred to a kneader, where ingredients such as bamboo fiber, wood cellulose, and lubricants are added and mixed thoroughly. The material is subsequently dried using hot air at 80–85°C until the moisture content falls below 3.5% (requiring approximately 3–4 hours). Finally, the material undergoes pulverization and ball milling (for 3–8 hours, while ensuring the material temperature does not exceed 50°C), is passed through a 60-mesh sieve, and is then packaged.

During compression molding, the curing temperature for melamine powder typically ranges from 130°C to 150°C; the addition of a small amount of an acid catalyst can increase the curing rate.

Applicable Standards

The current national standard in China is GB/T 13454.3-2013, "Plastics—Melamine-formaldehyde powder molding compounds (MF-PMCs)—Part 3: Requirements for selected molding compounds." This standard is a modified adoption of the international standard ISO 14528-3:1999. It came into effect on May 1, 2014, and a review in July 2025 concluded that it remains valid. Commercial melamine molding compounds often claim compliance with specifications such as DIN 7708, while products intended for food contact must meet safety certifications, including those set by the European Union for food-contact materials.

Applications

The primary application for melamine molding compounds is in food-contact tableware, including bowls, plates, dishes, cups, spoons, trays, and refrigerator storage containers. These products resemble porcelain in appearance, are resistant to breakage, and are suitable for mechanical dishwashing. Beyond tableware, melamine molding compounds are also used for electrical insulation components, as well as cups and tableware for the aviation industry.

Key Distinction from Urea-Formaldehyde Molding Compounds: Melamine molding compounds (Grade A5) are food-grade materials suitable for manufacturing tableware that comes into direct contact with food. In contrast, urea-formaldehyde molding compounds (Grade A1) are not permitted for use in food-contact applications due to the risk of free formaldehyde release. In the marketplace, there are instances of non-compliant practices where Grade A1 material is used to produce "imitation porcelain" tableware; therefore, caution should be exercised during procurement to distinguish between the two.