In this blog post, we’ll explore the history of nylon and the principles behind its synthesis through condensation polymerization, and examine how amide bonds and molecular structure contribute to nylon’s high abrasion resistance, strength, and durability.
Everyone has probably had the experience of trying to hide a hole in a sock as best as possible. But what if socks develop holes frequently? While it’s inevitable that holes will eventually form due to friction when wearing socks for a long time, it would be quite inconvenient if the material had low resistance to friction and holes appeared frequently. Today, a variety of fibers—including nylon, polyester, cotton, and polypropylene—are used in socks, but nylon has long been widely used as a material for socks and stockings due to its high abrasion resistance and strength. If nylon hadn’t been developed, people in the past would have had to rely more heavily on natural fibers that are vulnerable to friction, or endure the inconvenience of frequently mending socks whenever they got damaged or keeping several pairs on hand to rotate.
The history of nylon—which has become an indispensable part of our daily lives—began in earnest in the 1930s when American organic chemist Wallace Carothers and his research team conducted research on synthetic polymers. Nylon was developed as a synthetic fiber that possessed properties similar to silk but could be mass-produced using a new method, and commercial production subsequently took off. Initially, it garnered attention particularly for textile products such as women’s stockings, and during World War II, it was also used in military supplies such as parachutes. After the war, its range of applications expanded significantly to include clothing and various industrial products. Today, nylon is used not only in apparel but also in a wide variety of fields, including automotive parts, electrical and electronic components, packaging materials, industrial filaments, and engineering plastics.
The key reasons nylon can be applied across so many fields are its high abrasion resistance, strength, and toughness, as well as its ability to be molded into various shapes during the manufacturing process. These advantages are closely related to nylon’s chemical structure. Therefore, it is necessary to understand nylon’s synthesis method and structure. Nylon is a type of polymer. A polymer refers to a molecule with a very high molecular weight, formed by the repetitive linking of basic units, known as monomers. It is easier to understand if you think of a subway train. If you consider each of the train’s carriages to be a basic unit, then the entire train—composed of these linked carriages—can be thought of as a polymer. Polymers are produced through a polymerization reaction in which monomers are linked sequentially. A polymerization reaction is a process in which monomer molecules link together through chemical reactions to form polymer chains or network structures; typical examples include condensation polymerization, addition polymerization, and ring-opening polymerization. Condensation polymerization is one of the primary methods used to produce nylon, and nylon 6,6 is the most representative example of this type. The name “nylon 6,6” derives from the fact that the two monomers that make up the polymer—hexamethylenediamine and adipic acid—each contain six carbon atoms. Let’s take a closer look at the condensation polymerization reaction, focusing on the relatively easy-to-understand synthesis process of nylon 6,6.
Condensation polymerization is a type of polymerization reaction in which two or more monomer molecules react, causing small molecules such as water to be released and new bonds to form, thereby creating larger molecules. Nylon 6,6 is produced when two monomers—adipic acid (C6H10O4) and hexamethylenediamine (H2N(CH2)6NH2)—react. In this reaction, the carboxyl group (–COOH) of adipic acid reacts with the amino group (–NH₂) of hexamethylenediamine, releasing water (H₂O) and forming an amide bond. Since both monomers have reactive groups at both ends of their molecules, the reaction does not end after a single step; instead, they continue to react with other monomers to form long polymer chains. In other words, the polymer known as nylon 6,6 is formed through the repeated linking of adipic acid and hexamethylenediamine. To easily understand the condensation polymerization reaction, imagine people with two hands each holding hands and forming an endless chain. If you think of each person as a monomer, the hands on either side correspond to the functional groups capable of bonding with other monomers. As they link together, small water molecules are released, and new bonds are formed, connecting multiple monomers into a single long chain. The bond formed during this process is an amide bond (–CONH–). Because the C–N bond in an amide bond cannot rotate freely, it influences the structure and arrangement of the polymer chain; furthermore, intermolecular interactions, including hydrogen bonding, can form between amide groups. These interactions, along with the crystallinity and arrangement of the polymer chains, play a crucial role in nylon’s physical properties, such as high strength, toughness, and abrasion resistance. In nylon 6,6 in particular, strong hydrogen bonds between amide groups contribute to the polymer’s structural stability and mechanical properties.
Nylon, produced through a condensation polymerization reaction, exhibits properties such as high strength, toughness, and abrasion resistance due to the presence of repeating amide bonds within its molecules. Thanks to these properties, nylon has been applied in a wide range of fields, including textile products such as socks and stockings, as well as military supplies like parachutes, ropes, and industrial fibers. In particular, nylon is lightweight, durable, and relatively resistant to friction; it also has the advantage of being usable not only as a fiber but also as a plastic material, depending on the type and processing method. Because of these characteristics, it has been widely used as a synthetic fiber to complement or replace various natural fibers and has been utilized as a material for a wide range of textile products, including clothing such as blouses and shirts. Furthermore, today it is widely used not only as a simple clothing material but also as an engineering plastic. Its applications are extremely diverse, ranging from automotive parts, electrical and electronic components, and home appliances to precision technology, packaging films, cable sheathing, monofilaments, carpets, and industrial fibers. Therefore, if we imagine a world without nylon, we can surmise that the materials and manufacturing methods of the countless products we use would be quite different from what they are today. This is because nylon is not merely a fiber used to make socks or stockings; it is a versatile polymer material utilized in both textiles and plastics, based on its unique molecular structure formed through a condensation polymerization reaction. Therefore, whenever you see nylon products commonly encountered in daily life, it might be worthwhile to reflect on the polymer science hidden within them. Rather than getting annoyed every time a hole appears in a sock, we can reflect on how nylon has made our lives more convenient over the years. Furthermore, as time goes on, the range of applications for nylon and other polyamide materials is becoming increasingly diverse, and new grades and composite materials are continually being developed to meet the specific requirements of industries such as automotive, electrical and electronics, high-performance packaging, and industrial materials. We can expect nylon to continue contributing to the development of various industries as new fields emerge where its structural advantages can be utilized even more effectively.
