Polyamides are plastics that can be processed and shaped at high temperatures. Their special feature is a chemical relationship to proteins (i.e. protein substances), which makes them particularly suitable for the production of robust fibers for textiles.
Thanks to their outstanding physical properties, polyamides are also suitable as construction materials for a wide range of different applications. Its chemical nature gives materials made from PA plastics high resistance to organic solvents such as oil, gasoline and grease.
Polyamides are a whole class of thermoplastic materials, which is why it is difficult to give an exact structural formula. As is usual for plastics, the long chains of polyamide molecules consist of individual, regularly repeating building blocks. Common to all polyamide molecules is a characteristic bridge of nitrogen, oxygen and carbon, the so-called amide bond, which gives polyamides a chemical proximity to proteins. The following section of a polyamide molecule serves as an example:
Polyamides can be assigned to different groups depending on the manufacturing process, chemical or physical properties. The properties of polyamide can be modified by selective admixture of other fibers.
Polyamide 6 (also PA 6) is one of the two most commonly used polyamides. It can be spun into long and robust fibers, which are commercially available as Kevlar, Cordura or Perlon, among others.
Polyamide 66 (also PA 66) is the original nylon, which differs only slightly from PA 6 chemically, but is synthesized in completely different ways. Both of these polymers are produced using established processes and yield fibers of the highest quality.
Polyamide 11 (also PA 11, chemical: poly-11-aminoundecanoic acid) is a polyamide plastic that has not yet been widely used and is synthesized from natural materials. Chemical treatment of castor oil can form robust fibers whose production from renewable raw materials does not compete with plants originally intended for food production.
Polyamide 12 (also PA 12, chemically: poly-laurinlactam) is a polymer that differs from other polyamides in its physical and chemical properties. For example, it is soluble in benzene.
In glass fiber-reinforced polyamides, glass fibers are added to classically synthesized fibers during production. As a result, the plastics obtained gain in stiffness and toughness. In addition, stability and fatigue strength are increased. However, reinforcing polyamides with glass fibers leads to significantly increased abrasion at material edges, which is why this type of reinforced plastic is not suitable for sliding applications.
As a thermoplastic, polyamides have characteristic properties from which the special properties of this fiber for a large number of applications are derived.
Depending on the type, the density of polyamides is around 1.1 to 1.2 g/cm³ for the classic polyamides. The densities of poly-lauric lactam and poly-11-aminoundecanoic acid are slightly lower at 1.01 g/cm³, but still higher than that of water.
The question is repeatedly asked as to whether polyamides are waterproof. The answer is clearly "yes," which is why polyamide fibers are ideal for making waterproof clothing. Regardless of this, the water absorption of the synthetic fiber must be considered. Before further processing, polyamides must be carefully dried to prevent subsequent damage to the workpiece. This makes these components hard and brittle. For optimum development of their physical properties, polyamides must absorb a small amount of water. This results in a slight change in size, which must be taken into account in the production of polyamide workpieces.
Polyamides are waterproof and have a high resistance to organic solvents. However, they can be easily attacked by acids and oxidizing agents such as fluorine or hydrogen peroxide.
Depending on the chemical structure of the molecule, the application spectrum of polyamides ranges from -30°C to over 100°C, and even slightly higher for short-term applications. Around 200°C, the melting point of the plastic is reached, which makes proper use no longer possible.
Depending on the type of fiber, the types of synthesis of polyamides differ greatly from one another. What all polymers have in common is that they are produced from a single chemical building block, which can be attached to one another almost any number of times in the course of a chain reaction. Some plastics, such as nylon, can be spun into thread directly from the reaction mixture, which makes synthesis quite simple and convenient.
Polyamides are mainly used to produce fibers for the textile industry. Robust functional clothing made of polyamide prevents sweating, as the fiber wicks moisture away from the body and dries very quickly itself. A jacket made of polyamide fabric therefore effectively prevents the formation of sweat on the skin and is therefore used primarily in the areas of sports and outdoor.In addition to the use of polyamide fibers as clothing, this high-quality plastic is also used in a variety of ways in technology and crafts. Excellent mechanical resistance, good sliding properties and high tensile strength allow the construction of various materials of comparatively low weight.The wide range of applications of polyamides is evident in the following list:
Polyamide fibers are marketed as woven fabrics or solid plastics. Depending on the form, the processing methods thus differ.
Polyamide fibers can be dyed either directly during spinning or in later processing stages. The color fastness achieved with acid or metal complex dyes is very high.
Polyamides can be easily bonded together with solvent adhesives such as formic acid. For small bonding areas and bonding with other materials, superglue provides stable bonds.
Polyamides can be painted with water-based acrylic paint.
As typical thermoplastics, polyamides can be welded together under the specific action of heat. Specialized plastic welding equipment is available on the market for this purpose.
Polyamides are thermoplastics with a wide range of applications. As synthetic fibers, they are used in the clothing industry. Finished workpieces made of PA are characterized by high impact strength and corrosion resistance.
Nylon is the original PA 66, and the word nylon is not protected as a trademark.
Functional clothing is usually made of polyamides or polyester. Here, polyamide fibers have the higher stretchability and faster drying ability.
Polyamide fibers and elastane are often woven together to produce even more durable and stretchy garments.
Polypropylene can also be used to make fibers, but they are coarser and stiffer than polyamide fibers and also have only lower UV resistance.
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