Table of ContentsPolyurethane Manufacturing ProcessApplicationIntroduction of PU Coatings and Adhesives IndustriesCoatingsAdhesivesIntroduction of PU SealantIntroduction of PU ElastomersProcessing of PU ElastomersThermoplastic PolyurethaneThe Study of Polyurethane (PU) Manufacturing Process is complex and relies on knowledge of chemistry. This article will examine three crucial aspects of the polyurethane production process. The first part is the discussion of the manufacturing process of the material. He divides this study into three sections including the production of isocyanates, the creation of polyols and ultimately the production of polyurethanes. The second important discussion concerns the application of PU materials. This section is broad and identifies the main uses of polyurethane such as thermal insulation, production of soles, padding, in construction, among others. Say no to plagiarism. Get a tailor-made essay on “Why Violent Video Games Should Not Be Banned”? Get an original essay. There is also an introduction to the production and application of the following components: Coatings, adhesives, sealants and elastomers. The final part of the paper examines processing. of thermoplastic polyurethane. Polyurethane (PU) refers to a compound belonging to the polymer family. Simply put, polymer materials are a form of plastic but different in composition because they do not contain urethane monomer (Lazonby). The polymer is a product resulting from the production process of different materials. Otto Bayer and other of his colleagues were responsible for the first discovery of PU in 1937. They were working on other projects focused on producing polyurea from aliphatic diisocyanate and diamine. It was while working in the IG Farben laboratories in Leverkusen, Germany that the team discovered the formation of PU from aliphatic diisocyanate and glycol (Sharmin & Zafar 3). PU production continued but did not become commercially available until around 15 years ago. Mass production of this compound took place after World War II. Initially, Bayer extracted PU from toluene diisocyanate (TDI) and polyester polyols for mass production. However, between 1952 and 1954 he managed to obtain the compound from various polyester-polyisocyanate systems. Over time, polyether polyols gained popularity due to their low cost, ease of handling as well as improved hydrolytic stability, leading to their phase out. of polyester-polyols. Tetrahydrofuran polymerization was the process used by DuPont to produce the first polyether polyols in the form of poly(tetramethylene ether) glycol (PTMG). The compound was commercially available and DuPont later produced Lycra by combining PTMG and other compounds such as ethylene diamine. In 1957, the chemical industry saw the production of polyethylene glycols (Sharmin & Zafar 3). The chemist continued to transform PU from flexible foams into rigid foams that serve as blowing agents. However, there are other forms of blowing agents on the market, including pentane and carbon dioxide. Today, PU has many applications and is referred to as different types of plastic due to its superior properties in the final product. Polyurethane Manufacturing Process It is also important to understand the PU production process that chemists such as DuPont and Bayer still use to date. The first point is that the process involves an exothermic reaction between a mixture of alcohol and multiplemolecules of the hydroxyl group (-OH) with isocyanates. The molecular groups can be diols, triols or polyols. On the other hand, isocyanates must be multiple isocyanate (-NCO) groups such as diisocyanates or polyisocyanates. The reaction between the two molecular groups forms the urethane bond which is an essential component of a PU molecule (Lazonby). The original reactants dictate the resulting structural properties of a PU. Additionally, the use of the final product (polymer) depends on characteristics such as relative molecular mass. However, the manufacturing process can be explained by the reaction of the three compounds. The first part is the production of isocyanates. Industries consider TDI (toluene diisocyanate or methylbenzene diisocyanate) and MDI (methylene diphenyl diisocyanate or diphenylmethane diisocyanate) as the most critical form of aromatics and polyisocyanates. The first consists of two isomers and toluene (methylbenzene) serves as the first material in the reaction. It produces nitromethylbenzene after mixing with an acidic substance, for example nitric acid. Nitromethylbenzene nitration produces dinitromethylbenzenes. The next step is the reduction of dinitrobenzenes to amines. Chemists then combine the amines with phosgene by heating to create diisocyanates. This step takes place when the substances are in the liquid state with chlorobenzene as a solvent. But it is also possible to carry out this step in the gas phase. In such a case, the chemist must vaporize the diamines and then mix them with phosgene at around 600 K. At this point, the actual substance is an isomeric mixture of dinitro compounds consisting of 80 percent 2,4-dinitrotoluene (DNT) and 20 percent 2.,6-dinitrotoluene. In other words, it is necessary to have the diisocyanates in equal proportions to avoid incurring additional expenses to purify the mixture by distillation. Additionally, best practice foresees the production of PU with different properties using polyols capable of reacting with the 80:20 mixture. The production process of MDI is more sophisticated than that of TDI production. More and more processes are involved in the formation of MDI, resulting in a more versatile product. In most cases, MDI processes are used in the production of rigid foams. Unlike the case of TDI, where toluene is the raw material, phenylamine (aniline) and methanol (formaldehyde) constitute the raw materials of the MDI process. The amines produced in this case are known as methylenedianiline (MDA). However, mixing these amines with phosgene produces MDI just like when making TDI. Separation of the three isomers in the resulting mixture is possible by distillation. The second part of PU manufacturing concerns the production of polyols. These polyols account for at least 90 percent of total PU manufacturing. They can be in the form of either hydroxyl-terminated polyethers or hydroxyl-terminated polyesters. A particularity of these compounds is that their reaction with isocyanates aims to produce PU with particular properties. Therefore, the degree of molecular crosslinking depends on the molecular structure, size and flexibility of the chosen polyol. These aspects are also important because they influence the mechanical properties of the polymer. Some reactions with biopols such as soybean oil and epoxypropane reveal that the polymers can be derived from renewable sources. The production of polyurethanes constitutes the last step in the manufacturing of PU. This part involves the production of a linear polymer resulting from the reaction of two hydroxyl groups withTDI or MDI. A reaction between polyols containing multiple hydroxyl groups leads to the intertwining of long-chain molecules at their intermediate points. The particles crosslink during a stiffer polymer structure with improved mechanical characteristics creating a rigid PU. PUs also need to undergo various chemical reactions to control the formation process and produce the desired PU with specific properties. Different additives serve different uses in the manufacturing of PU. For example, catalysts are agents that accelerate the reaction process between polyols and polyisocyanate. Fume suppressants help reduce the rate of smoke generation when burning a PU. One of the most popular uses of PU materials is as blowing agents and surfactants. The additive, in this case, creates a PU in the form of foam in order to control the formation of bubbles. Therefore, the reaction produces a foam with a cellular structure. On the other hand, cross-linking of the molecular strands changes the structure of the PU and creates greater reinforcement. Therefore, physical structures increase the functionality of the PU. The pigments ensure that the PU contains sufficient colored polyurethanes for visibility and aesthetics. Plasticizers reduce density, making the product flexible. Flame retardants and fillers minimize flammability and respectively improve the rigidity of the final product. Essentially, the manufacturing process requires the combination of two main components in the right proportions. These elements generally consist of polyisocyanate and polyols in liquid state. The reaction produces a solid polymer in an elastic or rigid form. In some positions, the product contains gas bubbles in cellular foam. A foamed PU results in two possible ways, including physical blowing. This condition involves a liquid with a low boiling point. The next step is to mix the liquid with polyols. The liquid vaporizes over time because it involves an exothermic reaction. The air dispersed during the reaction produces a mixture of nucleation seeds. On the other hand, water is needed for chemical blowing to create carbon dioxide from the polyol-polyisocyanate reaction. The transformation of liquid into solid polymer causes the gas bubble to expand to the highest possible point.ApplicationIt is essential to emphasize again that the manufacture of PU differs from the production of other plastics. For example, chemical plants manufacture poly (ethane and propane) and sell it in the form of pellets, powder or any other substance. The process involves subjecting the polymer to hot and cold temperatures to allow it to be shaped. The properties of the product are substantially similar to those of the original polymer. However, PU is produced as a final product, notably in the form of large foam blocks. The manufacturer then cuts the blocks into smaller pieces. In most cases, foams serve as cushions or thermal insulation. The final reaction is a solid substance or a liquid reactant. The stiffness or flexibility of PU depends on the specific density levels of the PU. This aspect also influences the use of a particular PU material. For example, PUs are suitable materials for upholstery due to their low density, high flexibility as well as high fatigue resistance. Another frequent use of PU is the insulation of electrical equipment. PUs are the best solution for these machines due to their resistance to oils. Additionally, it is possible to increase the density during manufacturing to make the cablesresistant. Patients suffering from heart problems usually undergo a procedure to install artificial heart valves. Artificial valves are suitable because PUs have high levels of flexibility and biostability. The high flexibility ensures that the valves can expand and contract freely, just like the regular heart valve. PUs are also crucial in construction as they provide essential thermal insulation due to temperature variations. The adhesive properties also ensure that the building panels provide enough strength to hold the building together and that it lasts longer. Besides their durability and flexible physical properties, PUs are also good materials for shoe soles because they resist abrasion. Introduction of PU Coatings and Adhesives IndustriesPU is of crucial importance to the coatings and adhesives industries. PU coatings and adhesives have several similarities as well as differences in the manufacturing process as well as technological trends. Similarities in product format and overall usage reflect the need for specific polymer design and requirements. For example, both cases involve the use of an integral film, in a process that involves applying the film to a surface which will then be hydrated to adhere to the surface. Similarly, coatings and adhesives technologies involve reactive or non-reactive systems. The number of adhesives sold in the market is twice the number of PU coatings sold. However, it is impossible to have an exact measurement of PU consumption in the market due to the high formulation of the components and their diluted state. Ebrary.net estimates that PU accounts for at least 7 percent of the more than 800 pounds of adhesives and sealants used worldwide. Additionally, the chemical industry recorded a 1 percent increase in consumption between 2015 and 2012.CoatingsCoating is necessary for vehicles, cables, floors, walls, bridges and roads, among other areas. Ebrary.net reports that the coatings market has a turnover of around £1.5 billion. Its consumption rate generally reflects the strong demand for finished products requiring PU coating. This also indicates strong application in industrial and architectural industries. PU contains properties that enable durability, corrosion resistance and weather resistance, making it a suitable material for coating. The main purpose of a coating is to shield and protect these services from pollution or corrosion of any external substances. It also helps keep things like cables lasting longer and also makes surfaces look better (polyurethanes.org). In particular, vehicle coating ensures that the exterior part is high gloss to protect the car from corrosion or scratches while improving color retention. Japan is one of the countries with the highest consumption of PU coating. This situation could be the result of a large number of automobile assembly and architectural firms in the region. The same principle applies to the external parts of an aircraft. However, aircraft must also have surfaces covered in extreme temperature differences. Planes fly at high altitudes where temperatures can be scorching or freezing. Deck surfaces require coating to prevent the support beams from rusting (American Chemistry Council).AdhesivesOn the other hand, PU servesadhesive or binder. This is because the compound is very versatile, allowing the production of glues. History records that the modern development of polymer resins and sealants dates back to the early 1900s. The polymer industry began around the same time. Adhesives (resins) refer to substances used to hold two surfaces together and preferably in a permanent state. The process by which surfaces attach to each other is called adhesion. Phenol-formaldehyde adhesives used in the plywood industry were among the first forms of modern adhesives to be developed. However, the period between the 1940s and 1950s marked significant growth in adhesives and sealants due to the increasing demand for military aircraft. However, the durability of the aircraft's joints presented a significant challenge for the developers. Chemists solved this problem in the late 1970s by introducing advanced adhesive systems that are still used to this day. Adhesion occurs during the final phase of PU production. This step can produce either structural adhesives or non-structural adhesives. The first refers to resins that have strength as the central elements necessary for assembly. On the contrary, non-structural adhesives have lower tensile strength since they are mainly used for temporary fixings. Adhesives play a major role in developing green strength. This term refers to the process by which the PU material creates an initial bond layer before full curing. This aspect gives the elements a second type of protection. This also ensures that industries do not need to incur additional costs for clamping and holding materials. Physical properties include high shear and tensile strength (Part 3). Some of the industries that rely heavily on PU glues include the construction, furniture, and packaging industries (polyurethanes.org). PU glues have high resilience and strength which ensures that objects stay bonded together for a long time. Construction, packaging, transportation, furniture and footwear make up the largest market for adhesives and sealants in order of demand (ebrary.net). Industries have also discovered that the qualities of PU adhesives aid in the recycling of used vehicle tires to produce surfaces such as sports tracks. Recycling developments are essential to preserve natural resources. Fiberboard is a product made from PU binders combined with wood chips. At the same time, PU sealants are an essential component in the construction or manufacturing of materials requiring water-resistant and high-strength joints. The adhesive property of PU also ensures that the materials recover easily after being folded or pulled and the item does not lose its shape. It is also important to note that not all bonding agents are used for painting despite the use of PU adhesives and sealants for painting purposes (American Chemistry Council). Additionally, adhesive failure results from the inability of surfaces to adhere. Introduction of PU Sealant Sealants are substances used to attach two surfaces by filling the space between the surfaces. The process provides a protective coating. The use of sealants is closely related to that of adhesives. In fact, sealants are the perfect example of non-structural sealants. This situation results from the fact that both components play an essential role inassembly and added value of finished products (Part 1). The chemical structure of the two elements is almost identical. Just like adhesives, sealants are resistant to their environments of use. Other standard features include that at any given time the components are in liquid form to facilitate bond formation. Once the bond is complete, the substances harden. Adhesion is also possible by combining with other parts in an assembly. This process is essential to ensure the durability of the final product. However, sealants have better flexibility than adhesives. Construction, consumer products, transportation, aerospace, and electronics companies are some of the major sealants market segments. The construction industry leads the transportation and industrial markets in terms of demand. Although each market requires a specific type of sealant, synthetic sealants make up more than 70 percent of the market supply. Chemists note, however, that it is necessary to develop a multidisciplinary approach for successful application of both components. Pertie adds that the successful use of sealants or adhesives depends on the correct selection of materials. The user must also understand the process required for membership. The natural flow of liquid substance onto the surface of a substrate followed by the solidification of the element is an indicator of a successful adhesion process. Additionally, the adhesive material should not destroy the substrate surface. Examples of conventional sealants include silicones. On another note, it is essential to understand that external influences can affect the effectiveness of adhesive and sealant materials. Therefore, it is impossible to determine the lifespan of a glued surface. Introduction of PU Elastomers Another type of PU are cast elastomers. These are rubber-like polymers capable of stretching to great lengths (McKeen 5). In fact, these polymers stretch the most compared to other forms of PU. However, they return to their shape after the stretching force is removed. The functioning of elastomers can be compared to that of a spring. Additionally, elastomers can resist flow when deformed by external forces. Much like other forms of PU, the element of versatility allows cast elastomers to achieve the optimal physical properties necessary for the application of a specific task. At the same time, flexibility allows PU manufacturing industries to customize elastomers for use in different market segments. PUs can perform various functions for metals and ceramics due to the reliability of cast elastomers. When in rubber form, cast elastomers exhibit high resilience and flexibility. PU elastomers have diverse applications and offer a wide range of hardness and processing characteristics. This component exhibits high levels of resistance to high viscosity substances such as oil and gasoline as well as non-polar solvents. Another unique feature of this element is that only a few compounds can affect fully cured cast elastomers (McKeen 7). Oxidizing agents and other strong acids and bases are examples of factors that can affect fully cured elastomers. Popular cast elastomer products include skateboard wheels, forklifts, and pressure tires. PU Elastomer ProcessingPU thermoplastic elastomers (TPU) are a urethane material. Industries produce it in the form of granules, or pellets using different techniques.