Urea-formaldehyde molding compound—commonly referred to in Chinese as "Dianyu" powder (literally "electric jade" powder)—is a primary type of amino-based molding compound and belongs to the category of thermosetting plastics. It is based on urea-formaldehyde (UF) resin, combined with additives such as cellulose fillers (typically α-cellulose or wood pulp), lubricants, curing agents, and pigments. The material is produced through processes including kneading, drying, and either pulverizing or granulating, and is supplied primarily in powder or granular form.

Basic Definition and Nomenclature

Chemically, this material is a urea-formaldehyde (UF) resin, synthesized via the polycondensation of urea and formaldehyde in the presence of a catalyst. In industry classification, "A1" is a common, general-purpose grade, denoting an economical, UF resin-based compound. This is distinct from "A5" melamine-formaldehyde molding compound; the two differ significantly in terms of raw material costs and intended applications. A1-grade material is notably less expensive than A5-grade but is not suitable for food-contact tableware, whereas A5-grade is the standard material used for food-grade Melamine tableware.

Physical and Chemical Properties

Products made from urea-formaldehyde molding compounds feature a smooth, hard surface and vibrant colors. They exhibit excellent resistance to electrical arcing and flames, along with good electrical insulation properties. The material has a relative density of approximately 1.48–1.56 g/cm³, a heat deflection temperature ranging from 128–138°C, and a thermal decomposition temperature exceeding 200°C.

Regarding chemical resistance, these compounds are resistant to fats, oils, alcohols, and common organic solvents like acetone, as well as surfactants and weak bases. They can withstand weak acids for short periods but are not resistant to strong acids or strong bases. With an oxygen index of approximately 30%, the material is self-extinguishing without the need for external flame retardants, and its formulation is halogen-free.

It should be noted that urea-formaldehyde products can absorb moisture in highly humid environments and are not suitable for steam sterilization. During initial processing and early stages of use, trace amounts of formaldehyde may be released; therefore, processing facilities must be well-ventilated. Production Process Overview

The production process for urea-formaldehyde (UF) molding compounds—often referred to as "electric jade powder" (电玉粉) in Chinese—is relatively extensive, with resin synthesis and compounding/kneading serving as the critical stages. During resin synthesis, formaldehyde and urea are reacted via addition and condensation in a weakly alkaline environment (pH 7–8) at a molar ratio of 1:1 to 1.5. The temperature is maintained at approximately 85°C; once the mixture reaches the "cloud point" (the onset of turbidity), it is cooled and discharged. In the kneading stage, components such as α-cellulose filler, a curing agent (e.g., ammonium chloride), a lubricant (e.g., zinc stearate or lithium stearate), and pigments are added. The mixture is thoroughly blended, then dried, ball-milled, and sieved to produce the final product.

During compression molding, the temperature is typically controlled between 130°C and 150°C. If the temperature is too low, curing will be incomplete, resulting in poor surface gloss; if it is too high, the material may degrade and release gases, leading to a rough surface finish.

Applicable Standards

The current Chinese national standard is GB/T 3403.3-2013, "Plastics—Urea-formaldehyde and urea/melamine-formaldehyde powder molding compounds (UF- and UF/MF-PMCs)—Part 3: Requirements for selected molding compounds." This standard is a modified adoption of the international standard ISO 14527-3:1999. It came into effect on May 1, 2014, and a review in July 2025 concluded that it should "remain valid." Internationally, commercial products often claim compliance with specifications such as BS 1322, DIN 7708, and ISO 2112, and may also hold UL certification.

Applications

Urea-formaldehyde molding compounds are primarily used in applications that are cost-sensitive and require a specific aesthetic finish, but do not involve food contact:

Consumer Goods: Buttons, bottle caps, mahjong tiles, game pieces, ashtrays, flower pots, various types of handles, decorative items, and toys.

Electrical Components: Housings for switches and sockets, power strips, circuit breaker enclosures, insulating structural parts for instruments, and casings for low-voltage electrical equipment. Industrial components: mechanical parts, industrial instrument components, etc.