What Is Urea Formaldehyde? Structure, Features, and Applications
Urea Formaldehyde or urea methanal is a type of opaque thermosetting resin or polymer obtained as a result of the chemical reaction between urea and formaldehyde. Urea is a solid crystal obtained from ammonia, and formaldehyde is a highly reactive gas obtained from methane. Both chemicals react to form the urea formaldehyde polymer, in which formaldehyde acts as the crosslinker. The resins formed by the chemical composition of urea and formaldehyde are used in adhesives, plastics, particleboard, and moulded objects. The Urea-formaldehyde productions are nearly 20 million metric tonnes annually worldwide, and this is almost 80% of all the amino resins produced worldwide.
History & Synthesis of Urea-Formaldehyde
Urea formaldehyde resins are primarily made up of formaldehyde and urea, and these resins are formed in water with a pH level of 7 or above. In industries, urea resins are prepared by condensing urea and formaldehyde in an aqueous solution, and in this reaction, ammonia is used as a catalyst.
The Urea-formaldehyde was first produced in the year 1884 by Holzer. The first Urea formaldehyde resin plastics were introduced in the year 1896, and the patents for this thermosetting resin were first given to German and British chemists in the early 1920s. Later, in 1925, the British Industrial Plastics Ltd. came up with a more durable and lightweight urea resin called the Beetleware.
Around the 1950s, urea-formaldehyde was replaced by melamine urea formaldehyde, which was more durable. Later, melamine urea formaldehyde resin was used in moulded products for its more extended durability. Today, melamine urea formaldehyde resin is used in the production of wood panels to make the hold more solid and firm.
Urea Formaldehyde Uses
The uses of urea formaldehyde resin are many, and it is used extensively in industrial products and even in home decor products. In general urea formaldehyde products include decorative laminates, textiles, paper, sand moulds, wrinkle-resistant fabrics, cotton blends, etc. It is extensively used as an industrial adhesive and in wood glue. In the early years, it was used in the production of electrical appliances casing, such as desk lamps. It acts as an insulator and prevents electric shocks. It is also used in foams for creating artificial snow in movies.
[Image will be uploaded soon]
In the agricultural field, urea-formaldehyde is used as a rich source of nitrogen. The microbes found in the soil act on the urea-formaldehyde to decompose it into liquid nitrogen for the use of the plants. However, the action of microorganisms and the release of nitrogen depends on the temperature.
In its pure state, urea-formaldehyde can be strengthened using cellulose and can be tinted using a number of pigments to produce light, rigid, translucent, and colourful kitchen and home decor equipment.
In the cosmetics industry, urea-formaldehyde resin is used to make containers for storing cosmetic products due to its high resistance to chemicals. It is also used in many electrical appliances such as switchboards and wall outlets due to its high electrical resistance.
The urea formaldehyde polymer lacks the resistance to moisture, and therefore urea formaldehyde adhesive is used in the production of many wood products that are used for interior decorations only.
Health Hazards of Urea Formaldehyde
There are no health hazards of urea-formaldehyde unless formaldehyde is released from Urea-formaldehyde resins. When formaldehyde is released into the air with a concentration of more than 3.0-5.0 ppm, its effects on health are significant. High exposure to formaldehyde can increase the risk of cancer. When the concentration of formaldehyde begins to increase in air, it causes serious health hazards, such as watery eyes, irritation in the nose, cough, skin rashes, allergic reactions, burning sensation in the throat, nausea, and in some cases, it can even cause difficulty in breathing.
FAQs on Urea Formaldehyde: History, Synthesis, and Uses
1. What is Urea-Formaldehyde resin?
Urea-Formaldehyde, often abbreviated as UF, is a non-transparent thermosetting polymer belonging to the amino resin class. It is created through a chemical reaction between its two primary monomers, urea and formaldehyde. The resulting material is known for its high strength, hardness, and heat resistance, making it suitable for a wide range of industrial applications.
2. How is Urea-Formaldehyde resin prepared as per the NCERT syllabus?
The preparation of Urea-Formaldehyde resin involves a condensation polymerisation reaction. Initially, urea reacts with formaldehyde in a controlled, neutral or slightly alkaline medium. This first step forms intermediate monomer units, primarily mono- and dimethylol urea. Subsequently, these intermediate units are heated in a slightly acidic medium, causing them to polymerise and form a three-dimensional, cross-linked network structure with the elimination of water molecules.
3. What are the main uses of Urea-Formaldehyde resin?
Urea-Formaldehyde resin has several important applications due to its strong adhesive properties and durability. Key uses include:
- Adhesives: It is widely used as a glue for manufacturing particleboard, plywood, and medium-density fibreboard (MDF).
- Moulding Compounds: Due to its excellent electrical insulating properties, it is used to make electrical fittings like switches, sockets, and plugs.
- Textile Finishing: It is applied to fabrics like cotton to impart anti-crease or wrinkle-resistant properties.
- Decorative Laminates: It serves as a key resin in the production of laminates for furniture and countertops.
4. What are the monomers of Urea-Formaldehyde and their chemical formulas?
The two monomers that form Urea-Formaldehyde resin are:
- Urea: Its chemical formula is (NH₂)₂CO. It provides the amino groups (-NH₂) that are essential for the polymerisation reaction.
- Formaldehyde: Its chemical formula is HCHO. It acts as the cross-linking agent, forming methylene bridges that connect the urea molecules into a rigid polymeric structure.
5. Why is Urea-Formaldehyde classified as a thermosetting polymer and not a thermoplastic?
Urea-Formaldehyde is classified as a thermosetting polymer because it undergoes irreversible chemical changes upon heating to form a rigid, three-dimensional cross-linked structure. These strong covalent bonds cannot be broken by reheating. Therefore, once set, the polymer cannot be softened or remoulded. In contrast, thermoplastics have weaker intermolecular forces and can be repeatedly softened by heat and reshaped.
6. How does the cross-linked structure of Urea-Formaldehyde contribute to its properties?
The extensive cross-linking in Urea-Formaldehyde's three-dimensional network is directly responsible for its key properties. This rigid structure prevents polymer chains from sliding past each other, which imparts:
- High hardness and strength: The strong covalent network resists scratching and deformation.
- Heat resistance: The polymer does not melt upon heating but will char and decompose at very high temperatures.
- Chemical resistance: The stable, cross-linked structure makes it resistant to solvents and other chemicals.
7. Is Urea-Formaldehyde resin considered harmful to human health?
Yes, Urea-Formaldehyde resin can pose health risks. The primary concern is the emission of unreacted formaldehyde gas from the finished product, a process known as off-gassing. Formaldehyde is a known irritant to the eyes, nose, and throat, and is classified as a probable human carcinogen. Due to these concerns, the use of UF resins in indoor applications like furniture and panelling is often regulated to ensure formaldehyde emissions are below safe limits.
