Fibers, Part 6: Synthetic Fibers

This time, we'll be discussing synthetic fibers.

A link to the previous article is provided at the bottom of the page; please check it out there.

Synthetic fibers are fibers made from synthetic polymers, primarily using petroleum as a raw material.

Although relatively new among chemical fibers, they are so widespread that it's safe to say almost everyone owns at least one product made from synthetic fibers.

This time, we'll introduce the three major synthetic fibers:

"Nylon," "Acrylic," and "Polyester."

There are many other types, such as "Vinylon" and "Polyurethane."

Let's start with nylon.

Nylon was the world's first synthetic fiber, developed in 1938.

There are two types of nylon, divided into nylon 66 and nylon 6 based on the atomic bonding state.

Nylon 66 was developed first and is the mainstream in the United States and the United Kingdom.

In Japan and Germany, which developed later, nylon 6 is the mainstream. Domestic nylon 66 is manufactured by Asahi Kasei and Toray.

It is an extremely strong fiber, with a filament tensile strength of 4.2-5.7 (cN/dtex), which is higher than the 3.8-5.3 (cN/dtex) of polyester (filament), another synthetic fiber, and comparable in strength to linen (ramie).

It is also a very lightweight fiber with a specific gravity of 1.14.

Its advantages include being soft, wrinkle-resistant, easy to clean, and dyeing vividly.

Its disadvantages include lacking stiffness and body, being susceptible to acid, and yellowing when exposed to sunlight.

Next, let's discuss "acrylic."

Acrylic is a fiber primarily made from acrylonitrile.

Fibers containing 85% or more acrylonitrile are called acrylic fibers.

Fibers called acrylic-based (modacrylic) fibers contain only about 35% to 85% acrylonitrile.

Incidentally, the Kanekalon® and Protex® materials that our company sells are not acrylic, but are classified as acrylic-based materials.

While nylon, mentioned earlier, is mostly used in long fibers and less in short fibers, acrylic is mostly used in short fibers and less in long fibers.

This is due to the advantages of acrylic.

Acrylic's advantages include bulkiness, flexibility, heat retention, and good dyeability.

Its disadvantages include being prone to pilling and static electricity.

Its advantages are similar to wool, and it is often used in sweaters and blankets.

Finally, let's talk about "polyester."

There are various types of polyester, the most common being "polyethylene terephthalate," commonly known as PET. Other types include "polytrimethylene terephthalate" and "polybutylene terephthalate."

It is excellent in both price and performance, and is widely used not only in clothing but also in interiors and materials. Polyester is a highly versatile fiber, used in both long and short fiber forms.

Its advantages include high strength, stiffness, and high heat resistance.

Its disadvantages include poor dyeability due to low moisture absorption and low color fastness.

However, these drawbacks can be compensated for by dyeing at high temperatures.

In 2018, the production volume of chemical fibers was 879,611 tons, of which 696,042 tons were synthetic fibers.

Of that, polyester accounted for 200,387 tons, representing over 22% of total chemical fibers and over 28% of synthetic fibers.

These chemical fibers can be processed in various ways by human hands, allowing for the creation of new functionalities and modifications to compensate for the aforementioned drawbacks.

For example, flame retardancy, water repellency, anti-pilling (preventing pilling), moisture absorption, and split fiber yarn (microfiber) are among the various functionalities that can be developed.

Recently, sustainable synthetic fibers that are environmentally friendly have been developed, including those that partially use plant-derived raw materials or fibers recycled from discarded materials such as PET bottles.

Review of this lesson:

Synthetic fibers are fibers made from synthetic polymers.

There are many types, but among them, "nylon," "acrylic," and "polyester" are called the three major synthetic fibers.

Nylon is the first synthetic fiber developed. It is strong and lightweight, but lacks stiffness and body, and yellows in sunlight. It is mostly used as a long fiber.

Acrylic is a fiber made from acrylonitrile. Fibers with an acrylonitrile content of around 35% to 85% are called acrylic (modacrylic). Kanekalon and Protex, which our company handles, are classified as modacrylic fibers.

It has high bulkiness, heat retention, and good dyeability, but is prone to pilling and static electricity.

Unlike nylon, it is often used as a short fiber.

Polyester comes in various types, with PET (polyethylene terephthalate) being the most well-known. Because it is inexpensive and performs well, it is used everywhere. It is strong, heat-resistant, and has good stiffness and resilience. Its drawback is poor dyeability, but this can be overcome by dyeing at high temperatures.

Synthetic fibers are made by hand, so various functions can be imbued by the shape of the yarn and the incorporation of useful components.

Thank you for reading to the end.

Next time, I plan to write about "inorganic fibers."

References

Aichi Textile Promotion Association (2016) "TEXTILE HANDBOOK"

Teruhiko Ichimi (2014) "Easy-to-Understand Knowledge of Apparel Materials, Revised Edition" Seiunsha

Challenges in the Textile Industry and Initiatives of the Ministry of Economy, Trade and Industry

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