Polyamide Fibers
Almost at the same time, it was also discovered in Germany and manufactured under the trade name Perlon. It became possible to realize functional qualities in apparel that were previously out of the question.
Polyamide fibers are primarily used for clothing, in stockings and tights, lingerie, and corsetry as well as for sports and swimwear.
In Germany, 73,000 tons of polyamide fibers were manufactured in the year 2013.
Fibers made from polyamides are better known by their protected brand names, such as Nylon® and Perlon®. If you mix carboxylic acid groups with amino groups, you get polyamides, which is what the name says. Aramids and polyamides have very similar structures, but polyamides only have aliphatic carbon chains and no aromatic parts. These fibers are made by melt spinning, and most of the time, they are round. Fibers made of polyamide are durable and tough, and they also soak up water well. As well, they don’t react well with organic solutions chemically.
A fiber with many faces
In the manufacture of polyamide fibers, the primary materials are transformed by chemical processes into granules (tiny grains).
The granule is dissolved into a liquid or heated to produce a thick, syrupy spinning mass, which is pressed through the spinneret.
Additives or spinneret choice achieves the fiber’s predetermined properties. According to their profile and further processing, the fibers can be fine and smooth, crimped, bright, or dull.
On care labels, the polyamide fiber is often designated as “PA.”
Polyamide fibers are very durable and resistant to abrasion.
They have high elasticity.
They are light and fine.
They are easy to wash and quick-drying.
Polyamide fibers guarantee shape retention.
Polyamide (PA), commonly known as nylon, is a general term for thermoplastic resins containing repeating amide groups [NHCO]—on the main chain of the molecule, including aliphatic PA, aliphatic-aromatic PA and aromatic PA. Among them, aliphatic PA has many varieties, a large output, and a wide application.
Common polyamide fibers are mainly derived from two types of polymers. One is a polydiacid diamine, obtained by polycondensation of a diamine and diacid, with a long-chain molecular structure represented by the formula H-[HN(CH₂)xNHCO(CH₂)yCO]-OH. A typical example is polyamide-66, the chemical formula of which is shown in the figure below.
The other type is obtained by the polycondensation or ring-opening polymerization of lactam, whose chemical structural formula for a long-chain molecule is H-[NH(CH₂)xCO]-OH. A typical example is polyamide-6, the chemical formula of which is shown in the figure below.
Properties
- Polyamide has outstanding comprehensive properties, including mechanical properties, heat resistance, wear resistance, chemical resistance and self-lubrication, and has a low coefficient of friction, a certain flame retardancy, and easy processing.
- The moisture absorption capacity of polyamide fiber is among synthetic fibers, and the moisture regain can reach about 4.5% under normal atmospheric conditions.
- Polyamide fibers are alkali-resistant and acid-resistant, and their amide groups are easily acid-hydrolyzed, resulting in the cleavage of amide bonds and a decrease in the polymerization degree.
- Polyamide fibers have high strength, strong elongation and good elasticity. The strength of polyamide-6 and polyamide-66 fibers is 4~5.3cN/dtex, and the elongation is 18%~45%. When the elongation is 3% to 6%, the elastic recovery rate is close to 100%.
- The most prominent advantage of polyamide fiber is that its abrasion resistance is higher than that of most other fibers, which is 10 times that of cotton fiber, 20 times that of wool, and 50 times that of viscose fiber.
Structure
Molecular Structure
Polyamides have molecular rigidity and intermolecular hydrogen bonds. Amide groups can form strong hydrogen bonds between chains inside the fiber. Such strong hydrogen bonds can impart unique properties to polyamide fibers, such as high strength at high temperatures, toughness at low temperatures, outstanding elasticity, high resiliency, etc.
Fiber Structure
Polyamide is a flexible thermoplastic polymer, so it can orient and crystallize inside the fibers at high temperatures. Amorphous and crystalline domains differ in molecular orientation, chain mobility, chain packing, number of hydrogen bonds, and interchain space. This structural difference results in different responses in amorphous and crystalline regions to heat, chemicals, moisture, and loading.
Morphological model for nylon-6 fiber
Applications
In the civilian field, it is generally used to weave socks, scarves, clothing, etc.; in the industrial field, it can be used to manufacture tire cords, ropes, fishing nets, parachutes, etc.
Advantages of Polyamide Fiber
- Light weight, 1.14 grams per centimeter
- Chemical protection that is good to organic solvents
- Good resistance to wear and tear
- High ability to stretch
Disadvantages of Polyamide Fiber
- Not resistant to alkalis and acids in water
- Breakdown by oxygen at high temperatures
How to produce Polyamide fiber
Polyamides are made when carboxylic acid derivatives and amino groups join together and expand, which is also known as polycondensation. The carbon chains between the functional groups are aliphatic, not aramide-like, and can be different lengths. Either a dicarboxylic acid and a diamine polycondensate are used to make them, or a caprolactam polymerizes in a way that opens up its rings. The name of the polymer that is made can be used to figure out what polymerization method was used. If the polyamide is made from caprolactam, the product name has one number, like PA-6. When made through polycondensation, the product name has two numbers after it, like PA-610. A process called melt spinning is generally used to make fibers. In an extruder, polymer is melted and then turned into strands. Finally, spinnerets are used to make fibers. The process is finished by steps further down the line, like stretching and fiber finishing.
