What is Nylon Fiber? Properties | Applications

What is Nylon Fiber?

Nylon fiber is a polyamide fiber widely used in the textile industry due to its exceptional properties. It’s strength, durability, and elasticity make it a popular choice for industrial and consumer applications. 

History

In the early 1930s, Wallace H. Carothers, a chemist who worked for DuPont, started experimenting with polymers. Carothers aimed to create a new kind of fiber that was stronger and lasted longer than natural fibers like cotton and silk.

Carothers and his team made the first nylon fiber, which they called nylon 66, in 1935. Hexamethylenediamine and adipic acid are the two monomers that are used to make nylon 66. By combining these monomers, a long, chain-like structure is formed.

In 1938, a nylon-bristled toothbrush was the first product to be sold that was made with Nylon 66. It was very popular instantly, and soon nylon was being used in a lot of different things, like socks, ropes, and tyres.

During World War II, there was a huge rise in the need for nylon. Nylon was used to make blankets, parachutes, and other things for the military. After the war, the number of people who wanted nylon kept going up, and it soon became the most famous man-made fiber in the world.

In this article, we will discuss the properties, types, manufacturing, application, and uses of nylon fiber. Before we discuss nylon fiber, let’s know some basics about polyamide fiber.

What is Polyamide fiber?

An amide group connects repeating molecular units in polyamides, which are polymers. In a broad sense, proteins and peptides are included in polyamides, natural polymers consisting of amino-acid repeating units.

Types of Polyamide Fibre

There are two types of polyamide fiber: 

1. Aramide
2. Nylon
3. Aramide

Amide polymers that contain phenyl rings in their repeating units are called Aramide. When 85 percent of the amide groups are linked directly to phenyl rings, the polyamide is recognized as an aramid. There are different trade names for Aramide, such as Kevlar (Kevlar 2g, Kevlar 4g) and Nomax (Nomax 430-434, Nomax 450-453)

Aramide Polymers

Types of aramid

There are mainly two types of aramid fibers:

• Meta- aramid
• Para-aramid

Meta-aramid

Meta-aramid fiber is a special fiber that doesn’t melt or catch fire at a typical oxygen level. It has resistance to thermal, chemical, and radiation.

It can be used to make fire-retardant textiles for firefighters and Formula One car drivers. 

Example: Nomex, Teijiconex

Para-aramid

Para-aramid Fiber is produced by the para-aramid. It has higher strength. It is usually used in fiber-reinforced plastics topics for civil engineering structures, stress skin panels, and other high-tensile-strength applications.

Example: Kevlar, Twaron

Kevlar: Kevlar is one type of polyamide. It has para-phenylene groups between its amide groups. At carbons 1 and 4, the amide groups attach to the phenyl rings opposite each other.

Nylon

Nylon is a linear polyamide polymer with recurring amide groups (-CO-NH-) as an integral part of the molecular chain. 

It has a linear but zigzag arrangement of carbon atoms. Carbon atoms are arranged as the verticals of a triangular pyramid, i.e., a tetrahedron. This tetrahedral arrangement of bonds forms a zigzag but linear polymer. This is responsible for the good elastic properties of nylon. 

The polymer system of nylon is 65–85% crystalline and 15–35% amorphous.

Properties of Nylon fiber

Nylon has several properties that make it an ideal material for various applications. Here are some of the properties of this fiber:

1. Strength

Nylon fiber is known for its excellent strength, making it ideal for applications requiring high tensile strength. It is more vital than most natural fibers and can withstand heavy loads and stress.

2. Durability

Nylon fiber is highly durable and resistant to wear and tear, making it suitable for use in products that withstand frequent use and exposure to harsh conditions.

3. Elasticity

Nylon fiber is highly elastic, so it can stretch and return to its original shape without damage. This makes it suitable for use in applications that require flexibility and resilience, such as sportswear.

4. Heat Resistance

Nylon fiber has good heat resistance and can withstand high temperatures without melting or degrading. This makes it suitable for use in products that require heat resistance, such as automotive parts and electrical components.

5. Chemical Resistance

Nylon fiber is resistant to many chemicals, including acids and alkalis, making it suitable for use in products that come into contact with these substances.

Manufacturing of Nylon fiber

Nylon fiber is manufactured through a process called polymerization. In this process, the raw materials are combined and then heated to create a liquid polymer. The liquid polymer is then extruded through a spinneret, which produces long, continuous strands of this fiber. The fibers are then cooled, stretched, and wound onto bobbins for further processing.

Types of Nylon Fibre

There are several types of nylon, each with its own unique properties. Here are some of the most common types:

Nylon 6

Nylon 6 is a type of fiber that is made from caprolactam. It is known for its excellent strength and durability, making it suitable for carpets, fishing lines, and parachutes.

In a melt or fluid, caprolactam is polymerized to make nylon 6. The fibers are then made by spinning the polymer chains. There are a lot of different colours and weights of nylon 6 fibers that can be made. They are usually mixed with other fibers, like cotton or polyester, to make them better.

Flowchart of the Nylon-6 manufacturing process

Manufacturing process of Nylon 6: 

1. Raw materials: Caprolactam is the primary raw material obtained from coal tar.

2. The VK tube: VK tube refluxes back Caprolactam and allows water to evaporate.

3. Water feeding: The water fed to the VK tube is about 1–5% total Caprolactam. The water boils off instantaneously after being provided to the VK tube.

4. Water boiling: The boiling of water causes agitation on the top of the zone, and outgoing water vapours drive away any residual oxygen left on the surface of melt in the top site, thus protecting melt from oxidising.

5. Amino caproic acid formation: During the passage of melt in the tube, the Caprolactam ring opens up to form amino Caproic acid, which initiates the polymerization reaction.

6. Water removal: Water arising from polycondensation is removed in the form of vapours.

7. Polymerization: When the melt reaches the bottom of the tube, it gets fully polymerized and drowns at a constant rate with the help of a metering pump.

Nylon 6,6

Nylon 6,6 is a fiber made from adipic acid and hexamethylenediamine. It is known for its high tensile strength and excellent heat resistance, making it suitable for automotive parts, electrical components, and industrial textiles.

Flowchart of the Nylon 6 manufacturing process:

Manufacturing process of Nylon 6,6

Nylon 6,6 is a polycondensation-based semi-crystalline Polyamide fiber. The manufacturing process of this fiber is described below:

1) Firstly, Nylon 6,6 consists of a salt-like by-product, which is the result of a polycondensation reaction between hexamethylenediamine and adipic acid.

2) An evaporator then streams salt-like results into the tank. 

3) The solution was concentrated at 105°–115° C for 20–30 min to a rigid content of 60–75%.

4) They are then received by an intense pressure reactor at a temperature of 235°C for 2 hours and changed to a pre-polymer. Pressure is released at 260°–290° C in a flasher.

5) The polymer is then forced into a finisher that looks like a film evaporator. The nylon 6,6 polymer is fed at a temperature of 260°–290° for 5–10 minutes through a finisher and released from this until the required viscosity is fulfilled for the spinning of the finisher.

Difference between Nylon 6 and Nylon 6,6:

Nylon 11

Nylon 11 is a type of fiber made from vegetable oil. It is known for its excellent chemical resistance.

Nylon 11 is commonly used in a variety of products, including: 

• Fuel lines
• Hydraulic hoses
• Pneumatic tubes.

Nylon 12

Nylon 12 is a type of fiber that is made from laurolactam. It is known for its excellent elasticity.

Nylon 12 is commonly used in a variety of products, including:

• Sportswear
• Hosiery.

Applications of Nylon Fibre

Nylon fiber is used in various applications due to its exceptional properties.

Here are some of the most common applications of this fiber:

i. Textile industry

Parachute fabrics, cords, and ropes are made from high-tenacity nylon. Nylon has good dimensional stability. For this reason, ladies’ gloves, loose underwear, swimming wear, stockings, hosiery fabric, etc. are made from nylon.

ii. Automotive Parts

Nylon fiber is commonly used in automotive parts, such as airbags, seat belts, and fuel lines, due to its strength and heat resistance.

iii. Electrical Components

Nylon fiber is also used in electrical components, such as cable ties and insulators, due to its excellent heat and chemical resistance.

iv. Other Applications

Nylon fiber is also used in many other applications, including fishing lines, parachutes, medical sutures, and astroturf.

v. AstroTurf

Monsanto introduced AstroTurf, a brand of synthetic grass, in 1965. It is made of nylon fibers that are melted together with a backing material. AstroTurf is used in many places, like sports areas, playgrounds, and front and back yards

Conclusion

Nylon fiber is a versatile material widely used in the textile industry. Its exceptional properties, including strength, durability, elasticity, heat resistance, and chemical resistance, make it an ideal material for a wide range of applications. With its many types, manufacturing processes, and applications, this fiber will continue to be an amazing material for years.

Author
Mohammad Ibrahim
mdibrahimliman@gmail.com
Studying a BSc. in Textile Engineering, majoring in Apparel Engineering, at Textile Engineering College, Noakhali

Reference

• https://en.wikipedia.org/wiki/Synthetic_fiber
• https://leartex.com/nylon-fiber-properties-and-uses
• https://en.wikipedia.org/wiki/Nylon
• https://polymerdatabase.com/Fibers/Nylon.html
• https://www.sciencedirect.com/topics/medicine-and-dentistry/nylon-fiber