What is the difference between epoxy paint and polyurethane paint?

The most fundamental difference between them is that the film-forming substances are not the same. The film-forming substance of epoxy paint is epoxy resin, which is commonly used bisphenol A, bisphenol F, etc. The film-forming substance of polyurethane paint is polyurethane resin, which can be prepared by reacting isocyanate with alcohol.

Because the coating film is dense after epoxy resin curing, and water molecules are not easy to penetrate, epoxy paint is mostly used as an anti-rust primer. However, the benzene ring in aromatic epoxy paint is not UV resistant and cannot be used as a topcoat, otherwise it is easy to powder and fail. Polyurethane paint, its paint film is dense, scratch-resistant and has high gloss, so it is mostly used as a decorative topcoat.

Epoxy paints, which are used as topcoats, are also less resistant to discoloration than polyurethane.

After the epoxy paint is cured, if the paint needs to be applied on it, there is a maximum overcoating interval, beyond which the surface needs to be re-brushed before the paint can be applied. The polyurethane coating surface only needs to be treated more appropriately before the paint can be applied. However, it should be noted that epoxy paint as a primer can be compatible with many types of paints, in other words, epoxy coatings can be properly treated, and their surfaces can be applied to many types of other paints; Other types of paints that are compatible with polyurethane coatings are less likely to be overcoated by themselves.

1.Ingredients:

Polyurethane paint: It is a two-component polyurethane anticorrosive topcoat composed of synthetic resin as the base material, coloring pigment and curing agent.

Epoxy paint: It is composed of epoxy resin, physique pigment and curing agent.

2.Product Appearance:

Polyurethane paint: the paint film is plump, the color is bright, and the decoration is good.

Epoxy paint: Although the color is diverse and adjustable, it is slightly less decorative than polyurethane paint compared to polyurethane paint.

3.Usage:

Polyurethane paint: due to its plump paint film, rich and adjustable color, good decoration and other properties, it is mostly used as a topcoat. However, polyurethane paint has poor weather resistance and is easy to yellow, so it is suitable for metal protection in indoor environment, and is not suitable for outdoor use.

Epoxy paint: Because epoxy paint has poor weather resistance and is easy to chalize, it is mostly used as a primer, such as indoor steel structure, mechanical equipment and other anti-corrosion coatings can also be used as topcoats. Epoxy primers are versatile and have excellent supporting properties.

4.Corrosion Resistance:

Polyurethane paint: Polyurethane topcoat has strong acid resistance.

Epoxy paint: Epoxy paint has strong alkali resistance, and the damp heat resistance of epoxy paint is slightly better than that of polyurethane paint.

1. The composition is different.

Epoxy paint is composed of epoxy resin, physique pigment and curing agent.

Polyurethane paint is polyurethane paint. It has a strong paint film, full gloss, strong adhesion, water resistance, wear resistance, and corrosion resistance.

2. The application is different.

Polyurethane lacquer is widely used in high-end wood furniture, but also on metal surfaces. Its shortcomings are mainly blistering in case of moisture, paint film powdering and other problems, and polyester paint, it also has the problem of yellowing. The varnish variety of polyurethane paint is called polyurethane varnish.

Epoxy paint is suitable for painting the inner wall of oil tanks, and can be widely used on the surface of various light metal and cement structures indoors and outdoors, and can be coated in railway bridges, high-voltage transmission towers, containers, offshore drilling and oil production equipment, various vehicle chassis, heavy machinery, ships, chemicals, equipment and pipelines, and gas engineering gas storage cabinets used in different environments.

3. The characteristics are different.

Polyester paint is characterized by the formation of non-cyclic and or annular hydrogen bonds between polymer molecules, which can be separated and absorb external energy (20 25kj per mole) under the action of external force. When the external force is removed, hydrogen bonds can be formed again. This reversible repetition of hydrogen bond cracking and re-formation gives the polyurethane paint film a high degree of mechanical wear resistance and toughness.

The outstanding advantages of cured epoxy resin are that it is chemically stable, alkali-resistant, air-resistant, and oil-resistant. This is because there are no ester bonds in the epoxy resin, and the aliphatic hydroxyl groups contained in it do not react with the alkali, and the paint cured product has a three-dimensional mesh structure. Therefore, epoxy resin coatings are often used as anticorrosive primers, oil baths and other inner walls.

However, the acid resistance of epoxy paints is generally poor.