Difference Between Epoxy Polyurethane and Polyurethane

The so-called epoxy polyurethane is a process in which epoxy resin with high hydroxyl content reacts with isocyanates (monomers or prepolymers such as TDI, MDI, HDI, etc.) as part of a hydroxyl component or component.

Polyurethane: Abbreviation"pu", which is the reaction of hydroxyl or amino components with isocyanates (monomers or prepolymers such as TDI, MDI, HDI, etc.). There is a lot of room for choice of hydroxyl and amino components (for example, hydroxyl polyester resin, castor oil, polyether polyol, etc. can be selected for coatings; In the case of thermosetting polyurethane elastomers, it is the use of small molecule hydroxyl and amino components as curing crosslinkers), and because of this, polyurethane is widely used

From foams, coatings, elastomers to fibers and more.

The two are different materials for the production of flooring, which are selected according to the requirements of use.

Polyurethane floor coating refers to a kind of floor coating with polymer compounds containing repeated urethane (-NHCOO-) characteristic units in the molecular backbone structure as film-forming substances; The film-forming material of generalized polyurethane floor coating is not limited to polyurethane, but also includes polyurea and polyurethane polyurea hybrids, the so-called polyurea refers to a class of polymer compounds containing repeated ureaformate (NHCONH) repeating structural units in the molecular backbone structure.

Epoxy resin is a type of synthetic resin that contains more than two epoxy groups in its molecular structure and can be crosslinked. The epoxy group is a ring composed of one oxygen atom and two carbon atoms, namely -c-c-o, which has a high degree of activity, enabling the epoxy resin to cross-link with various types of curing agents to form a polymer with a three-dimensional network structure. The properties of epoxy resins have an important relationship with molecular weight:

Low molecular weight epoxy resin has high hardness, high brittleness, and low impact strength; Linear epoxy resin has strong adhesion and poor water resistance, and volatile coatings are mostly used; Medium molecular weight epoxy resin hardness, moderate flexibility.

First, the composition is different.

1. Epoxy polyurethane: it is a two-component self-drying paint, the first component is polyester color paste, and the second component is a special curing agent.

2. Polyurethane: It can be divided into two-component polyurethane coating and one-component polyurethane coating. Two-component polyurethane coatings are generally composed of isocyanate prepolymers (also called low-molecular-weight urethane polymers) and hydroxy resins, which are commonly called curing agent components and main agent components.

Second, the use is different.

1. Epoxy polyurethane: widely used in the coating of indoor industrial products and wood furniture with high requirements.

2. Polyurethane: This kind of paint film is bright and plump, hard and wear-resistant, oil-resistant, acid-resistant, chemical-resistant and industrial waste gas, has good electrical properties, can be miscible with a variety of resins, and can adjust the formula in a wide range to meet different needs. It is widely used in wood, automobiles, aircraft, machinery, electrical appliances, instrumentation, plastics, leather, paper, fabrics, petrochemicals and other aspects.

Third, the performance is different.

1. Epoxy polyurethane: epoxy polyurethane paint has good decorative and mechanical properties, high hardness and wear resistance, and has the characteristics of water resistance, oil resistance and solvent resistance.

2. Polyurethane: The characteristics of one-component polyurethane paint: it has good wear resistance, alkali resistance, oil resistance and solvent resistance, but it has poor weather resistance and is not suitable for outdoor use.

Characteristics of two-component polyurethane paint: hydroxyl curing polyurethane paint has the advantages of being able to dry at room temperature, low toxicity, tough paint film, high gloss, good adhesion, erosion resistance, oil resistance and water resistance.

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.

First, the chemical composition is different.

Polyester is a general term for polymers obtained by polycondensation of polyols and polyacids. It mainly refers to polyethylene terephthalate.

PET), which is also commonly included with polybutylene terephthalate.

PBT) and polyaryl esters. Polyester elastomers (TPEEs) are generally composed of dimethyl terephthalate, 1,4-butanediol and polybutanol.

polymerized, the chain segment includes a hard part and a soft part, which is a thermoplastic elastomer.

Polyurethane is a urethane group in the backbone of a macromolecule.

The polymer is called polyurethane.

Polyurethanes are divided into polyester polyurethane and polyether.

There are two categories of polyurethane. The structure of polyurethane is also difficult to represent with an exact structural formula. But there must be isocyanates in its macromolecular structure.

End groups, ester or ether bonds, carbamate groups, substituted urea groups, urea carbamate groups, and biuret groups.

Second, the chemical properties are different.

Polyester is a polymer compound.

It is made from terephthalic acid (PTA) and ethylene glycol.

eg) is polycondensed to produce wide clumps of polyethylene terephthalate (PET), part of which is finally formed by underwater pelletizing. Fiber-grade polyester chips are used to manufacture polyester staple fibers and polyester filament yarns, and are the raw materials for polyester fiber enterprises to process fibers and related products.

Polyurethane is a polymer that contains urethane groups in the backbone of macromolecules, called polyurethane, or polyurethane for short. Polyurethane is divided into two categories: polyester polyurethane and polyether polyurethane. The polyester type is a polyurethane prepared from diisocyanate and hydroxyl polyester.

Polyether polyurethane is a polyurethane prepared from diisocyanate and hydroxyl polyether.

Third, the main uses are different.

Fiber-grade polyester chips are used to manufacture polyester staple fiber and polyester filament, which is the raw material for polyester fiber enterprises to process fiber and related products, and polyester is also used in bottles, films, etc., which are widely used in the packaging industry, electronic appliances, medical and health, construction, automobiles and other fields, among which packaging is the largest non-fiber application market for polyester, and it is also the fastest growing field of PET.

Polyurethane is mainly used as polyurethane synthetic leather, polyurethane foam, polyurethane coatings, polyurethane adhesives, polyurethane rubber (elastomers) and polyurethane fibers.

Wait. In addition, polyurethane is also used in civil engineering, site drilling, mining and petroleum engineering, playing the role of blocking water and stabilizing buildings or roadbeds; It is used as a pavement material for running tracks in sports fields and indoor floors in buildings. Fighting.

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.