Melamine From Urea
Tech Blog melamine from urea Melamine is well-known for its wide range of applications, but its raw material for production is surprisingly urea. For manufacturers,
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Urea, with the chemical formula CO(NH2)2, is a simple organic compound that plays a central role in global agriculture, industry, and biology.
To truly appreciate the importance of urea, it is necessary to understand its unique physical and chemical properties. These properties not only determine how it is stored and transported, but also determine its functionality and reaction modes in different applications. This article provides a comprehensive guide to selecting the physical and chemical properties of urea.
At standard temperature and pressure, urea appears as a white, odorless crystalline solid, often processed into prilled urea or granular urea particles to enhance solubility and mixing.
The melting point of urea is clear, at 132.7 ℃. Unlike many organic compounds, urea has no boiling point and decomposes directly when its temperature exceeds its melting point. At around 160 ℃ (320 ℉), urea decomposes into ammonia (NH3) and cyanic acid (HNCO) – a reaction that limits its application in high-temperature industrial processes, but is used in specific resin production processes, such as urea-formaldehyde resin. In cosmetic applications, urea does not come into contact with such high temperatures during formulation and use, so its thermal stability fully meets the requirements.
One of the most important physical properties of urea is its high solubility in polar solvents, especially in water.
The solubility of urea in water: At 20 ℃ (68 ℉), about 108 grams of urea can be dissolved in 100 milliliters of water, a much higher solubility than many similar nitrogen-containing compounds. And solubility increases with temperature: at 100 ℃ (212 ℉), the amount of urea dissolved in 100 milliliters of water can reach about 167 grams.
Urea solubility in other solvents: Urea is also soluble in polar solvents such as ethanol, methanol, and glycerol, but insoluble in non-polar solvents such as benzene, ether, and fats.
The density of solid urea is about 1.32 grams per cubic centimeter, with a lightweight texture and easy transportation—this advantage is particularly prominent in agricultural and industrial applications.
Meanwhile, urea is hygroscopic, meaning it can absorb moisture from the air. Although this characteristic may cause granular urea to clump when stored in a humid environment (which can be resolved by adding anti-caking agents), it is beneficial in cosmetics. In moisturizing products, urea’s ability to absorb environmental moisture helps lock moisture into the skin.
Urea itself is a neutral compound, but due to the slight hydrolysis of its amino group (- NH ₂) in water, the pH value of its aqueous solution will exhibit weak alkalinity. At 25 ℃ (77 ℉), the pH value of a 10% urea aqueous solution is approximately 7.2-8.0, which is close to the pH range of human skin (usually 4.5-6.5). This characteristic makes it extremely low in irritation when used in cosmetics.
It should be noted that the pH value of urea aqueous solution may fluctuate slightly with concentration and temperature: the higher the concentration, the degree of hydrolysis may slightly increase, and the pH value will slightly rise, but usually not exceed 8.5; An increase in temperature may also accelerate hydrolysis, resulting in a slight change in pH.
Urea is prone to hydrolysis (reaction with water) under specific conditions, such as the presence of enzymes, heat, or alkaline environments.
Reaction process:
CO(NH2)2 + H2O → NH2COONH₄
NH2COONH₄→2NH₃+CO2
In nature, urease (present in soil bacteria and plant roots) accelerates this reaction, which is crucial for agricultural urea: the ammonia released during hydrolysis is converted into nitrate, which plants absorb as a nutrient. In cosmetics, hydrolysis is minimal at room temperature, ensuring that urea remains stable in the formula.
When urea is heated above its melting point, it decomposes into biuret and ammonia.
Reaction process: 2CO(NH2)2 → H2N-CO-NH-CO-NH2+ NH3
Industrial processes strictly control temperature to avoid the production of harmful by-products. For example, fertilizer production restricts heating to prevent urea formation, while resin manufacturing uses controlled decomposition to produce crosslinked polymers.
Due to the presence of lone pair electrons on the nitrogen atom in the molecule, urea exhibits weak alkalinity. It can react with strong acids to form salts.
Reaction process (taking nitric acid as an example): CO(NH2)2 + HNO₃ → CO(NH2)2·HNO₃
This compound is used in explosives and fertilizers.
Urea can undergo a condensation reaction with formaldehyde to form urea formaldehyde resin.
This is one of the primary uses of urea in industry. Urea-formaldehyde resin is an essential thermosetting plastic widely used as an adhesive for plywood, particleboard, and medium-density fiberboard, as well as for molded products and coatings.
Physically, it is an easy-to-handle, highly soluble solid, making it an ideal fertilizer that dissolves readily and is readily absorbed by plant roots.
Chemically, its reactions provide the necessary nitrogen source for plants; its thermal series characteristics require quality control in production and use; and its responses with aldehydes opened a promising path for the chemical industry, creating a range of products from furniture to automotive parts.
In summary, urea is far more than just a simple compound. Its unique physical and chemical properties make it a key bridge connecting biochemistry, agricultural science, and industrial manufacturing, with an inevitable and lasting impact on our modern world.
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