Discovery of polyurethane
Polyurethane polyurethanes were first discovered by Otto Bayer in Germany in 1937, and since then these materials with special properties have greatly advanced in various industries around the world. The first polyurethanes were produced by the reaction of diisocyanate. Alitanes are compounds that have urethane bonds in their structure.
Polyurethane (PU) is the common name for urethane-bonded polymers. The urethane bond is formed by an additive reaction between an isocyanate group and an active hydrogen compound such as a hydroxyl group. Isocyanate groups are highly reactive and therefore do not require temperature increase to develop their reaction. (The reaction takes place at ambient temperature) The most important feature of this group of polymers is that they form a stable structural reaction. In general, polyurethane can be produced in various forms such as foam products, films, elastomers, powders, liquids and emulsions. Compounds that have the isocyanate group are:
2, 4 or 2 and 6 toluene di isocyanate
4, 4 or 2 and 4 diphenyl methane di isocyanate
1 and 6 hexamethylene diisocyanate
In addition to the above, there are other isocyanate compounds. Compounds that have two groups of hydroxyl (OH) or more are called polyols, and the following types are commonly used:
Polyester Polyol
Polyester Polyol
Polycarbonate Polyol
Polycaprolactone Poly L.
In addition, instead of hydroxyl groups, compounds such as carboxylic acids and amines that contain active hydrogen can also be used in combination with isocyanates. For this reason, when it comes to polyurethane, we can say that there are countless varieties of them. From what has been said, it can be concluded that polyurethane is used in various applications such as: soft foams, hard foams, elastomers, adhesives, coatings and colored bases.
Applications of polyurethane polymer
Polyurethanes come in a variety of forms including soft foams, hard foams; Elastomers, thermoplastic elastomers, resins, paints, coatings, etc. are used in the world. One of the applications of polyurethanes is used as a cover for pipes buried in the soil in order to protect against corrosion.
The polyurethane used in this method is 100% solid and with polyurethane raw materials in special application conditions such as high temperature pipelines or repairs of the main coating are used and less used as the main coating of transmission lines.
The use of polyurethane coatings for the inner coating of transmission lines has a very limited application and is not recommended for the inner coating due to the release of toxic isocyanate compounds. The use of polyurethane compounds is also constantly evolving.
Polyurethane and silicone mastics have different applications due to their chemical and mechanical properties. In canals and water and sewage tanks, flooring of halls, sidewalks, joints of prefabricated parts and all joints that must be protected against the penetration of water and other liquids, and also used to make shoe soles.
How to make polyurethane compounds
Mixing polyurethane with polyurea is common and has a growing trend. Polyurethane is a class of versatile polymers with excellent properties. Therefore, designers and coatings industry professionals are well able to use these compounds in a variety of applications, including clear coatings for single-layer roofing coatings and paints used to identify pedestrian crossings.
Polyurethanes have excellent resistance to impact wear and cracking, including fast and complete curing at room temperature. Aliphatic polyurethanes are more expensive than aromatic types. That is why aromatic types and epoxy samples are used in esters, base paints and interface coatings. While aliphatics are for the final coating.
The use of protective coatings to prevent corrosion in steel structures with primers and base coatings of epoxy systems are examples of important applications of polyurethane.
Another case is floor covering systems in which all kinds of base coatings can be used, sometimes the final urethane coating is sufficient for the final floor layer. Application of polyurethanes and polyureas in flooring Types of technologies Application of floor coverings are all based on two principles. One of them is thin film technology, in which one or more coatings with a thickness of about 50 to 125 microns are applied on the floor surface. Sealing and dust removal are also among the important steps in this method, the ultimate goal of which is to achieve floors with small and ornate designs.
Polyurethane is a widely used polymer
In the late 1980s, a number of chemists studied the structure, structure, and morphology of polyurethane surfaces, and new methods of surface coating, along with bonding of other materials to polyurethane surfaces, were gradually developed to improve blood compatibility.
Polyurethane elastomers are a family of fractionated mass copolymers that have found important applications in various industrial and medical fields. The first polyurethane was obtained by the reaction of aliphatic diisocyanate with diamine. Otto Bayer and colleagues first introduced this polyurethane, which was highly hydrophilic and therefore could not be used as plastic or fiber. The reaction between aliphatic diisocyanates and glycols led to the production of polyurethane with plastic and fibrous properties. Subsequently, using aromatic diisocyanates and very high molecular weight glycols, polyurethane was obtained, which is an important family of thermoplastic elastomers.
The properties of urethanes vary from very hard thermoset materials to soft elastomers
he does. Thermoplastic polyurethanes are used in the manufacture of very important implantable devices, because they have good mechanical properties such as tensile strength, toughness, abrasion resistance and resistance to degradation, as well as good biocompatibility, which makes them suitable materials for applications. Puts medicine.
