Acrylic Fibre

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Acrylic fibre is a man-made fibre, made from a synthetic polymer called acrylonitrile [-CH2-CH(CN)-] (FTC definition). The acrylic fibres are very different from the melt-spun synthetic polymer fibres; they also differ more among themselves. Acrylic fibres are produced by two basic methods of spinning (extrusion), dry and wet.

Acrylic fibres are synthetic fibres made from a polymer (polyacrylonitrile) with an average molecular weight of ~100,000, about 1900 monomer units. The comonomer is added to improve dyeability and the textile processability of the acrylic fibre. This type of fibre is produced by reacting certain petroleum or coal-based chemicals with a variety of monomers, which means that acrylic fabric is a fossil fuel-based fibre.

Acrylic fibre can be supplied as producer-dyed either by pigmentation of the dope or with jel dyeing systems. It can be used 100% alone, or in blends with other natural and synthetic fibres. Since acrylic fabric is one of the least breathable forms of textiles in the world, it is desired in heat-retention applications. For instance, it is commonly used in athletic equipment, and it’s common to see tracksuits, hoodies, and athletic pants made from acrylic fabric. However, there are concerns that acrylic may be carcinogenic, so it may be prudent to avoid contacting this fibre with your skin.

Acrylic fibre is a synthetic fibre that closely resembles wool in its character. According to the definition of the ISO (International Standards Organization) and BISFA (International Synthetic Fibre Standardization Office), fibres which contain a minimum of 85% acrylonitrile in their chemical structure are called “Acrylic Fibres”. Depending on the compounds that acrylonitrile is mixed with, the final fabric will have different attributes.

China is the global leader in acrylic fabric production. While China is the largest acrylic fabric producer in the world, the title of largest acrylic fibre-producing company goes to the Indian firm Aksa Akrilik Kimya Sanayii AŞ. The next-largest acrylic-producing company is also Indian, but the Chinese firm Dralon takes third place.

History

The Dupont Corporation created the first acrylic fibres in 1941 and trademarked them under the name “Orlon”. This firm had already become famous around the world for the development of nylon and the mainstreaming of polyester production, and when acrylic fibre was invented in the 1940s, the world saw this development as simply the next step in DuPont’s rapid ascent to a dominant position in the world’s textile markets.

However, a golden age of acrylic fibre began in 1950s. Acrylic fibres became well known under trade names such as Orlon, Acrilan, Zefran, Creslan, and Courtelle: modacrylics included Dynel, Teklan, and Verel. It’s possible that the success of DuPont’s other synthetic textiles contributed to this slow mainstreaming of acrylic fibre; this company had already replaced silk with nylon and cotton with polyester, which may have reduced consumer receptivity to this company’s new wool replacement, acrylic.

Over the period of around a decade, the benefits of acrylic became more apparent, and this fabric gained greater and greater market share. At the time, consumers and industrial players were optimistic that synthetic fibres would eventually replace natural textiles altogether. Gradually, however, consumers became concerned about the flammability of acrylic, especially given the fact that wool, which acrylic was supposed to replace, has one of the best flammability profiles of any fabric.

By the 1970s, the environmental movement had soured public opinion against synthetic fabric, and at around the same time, information about the potential toxicity and carcinogenic attributes of acrylic was also coming to light. While the popularity of synthetic fibres in the United States has encountered a steady decline over the last few decades, the opening of other markets in Asia and Africa has helped keep the production of acrylic fibre afloat.

DuPont, however, is no longer the foremost producer of acrylic fibre. Other companies in China, India, Indonesia, and other ASEAN countries have supplanted this American manufacturer as the leaders of the acrylic fibre market. Similarly, the American consumer market demands far less acrylic fabric than emerging markets in developing countries do.

The market share of both acrylic and modacrylic fibres has declined somewhat since the 1980s, and although generically separate, it is appropriate to discuss them together.

 

Preparation of Acrylic Fibre

All commercial acrylic fibres are prepared using wet or dry spinning methods. Melt spinning cannot be applied because the acrylic polymers degrade upon heating. Polymers are dissolved in the appropriate solvent to form a spinning dope.

Acrylic fibre is generally made in facilities that also produce other forms of synthetic textiles. To begin the process of acrylic fabric production, the acrylonitrile polymer polyacrylonitrile is created in a water-based solution using a reaction technique called free radical polymerization.

This polymer is dissolved using a powerful chemical solvent, and the resulting gel-like material is then ready to be extruded through a spinneret to form acrylic fibre. These fibres are usually coagulated in a solution of the same solvent, which is called wet spinning.

However, a process called dry spinning can also be used, which is more efficient and environmentally friendly. Dry spinning involves evaporating the solvent with a stream of heated gas.

The resulting fibres are then washed, stretched, and crimped to make long, thin filaments that can be spun into yarn. Like other synthetic textile fibres, stretching is necessary to create a usable end textile; the process of stretching fibres like acrylic renders them many times their original length, which reduces costs and results in more production efficiency.

Once acrylic fibres have been spun into yarn, they are loaded onto bobbins and shipped to textile product manufacturers. These manufacturers then weave this acrylic yarn into apparel, carpeting, or a variety of other applications, or they may sell the yarn as-is with minor alterations as supplies for knitting hobbyists.

Either at the manufacturing plant or the textile product production facility, workers may also expose acrylic fibre to various dyes and treatments. For instance, flame retardants are strictly necessary for acrylic fabrics; without these admittedly toxic treatments, acrylic fabric would be highly dangerous.

There are three methods in solution spinning to produce acrylic fibre: dry spinning, wet spinning and air-gap wet spinning. Figure below shows schematic diagrams of these methods.

In dry spinning, DMF is used mainly as a solvent on account of its low boiling point and low cost. The air temperature is heated to 200°C in order to evaporate the DMF. However, DMF is not completely removed and 5–25% of the DMF remains in the undrawn fibre. The quantity of solvent remaining is dependent on the air temperature, column length and take-up speed. The remaining DMF helps orientate the molecular chains in the following drawing process. The rate of solvent evaporation in the fibre increases with increasing air temperature but the orientation of the molecular chain decreases.

In the wet spinning method, the spinning dope is extruded through a spinneret containing 20 000–100 000 holes with diameters of 0.05–0.25 mm. The spinneret is immersed in the coagulation bath and the fibres are solidified as they are removed from the spinneret through the substitution of solvent and non-solvent in the fibre. The solidification speed is affected by the concentration of the spinning dope, the ratio of solvent/non-solvent and the temperature of the coagulation bath. The rate of solidification increases with increasing concentration of the spinning dope and amount of non-solvent in the coagulation bath. The temperature of the spinning dope and coagulation bath is generally 25–125°C and 0–50°C, respectively.

Air-gap wet spinning is a modification of wet spinning and the spinneret is placed approximately 1 cm above the coagulation bath. Since the spinneret is not immersed in the coagulation bath, the temperature of the spinning dope can be controlled independently regardless of the coagulation bath temperature. Molecular chains in the fibre can be highly oriented because coagulation does not occur immediately after extrusion and there is no resistance in the coagulation bath. Therefore, the high take-up speed and high tenacity fibre can be obtained by air-gap wet spinning.

The fibres obtained from either a wet spinning coagulation bath or a dry spinning column have low strength and high elongation. Such undrawn fibres should be drawn in order to have reasonable mechanical properties. Drawing causes the polymer chains to become oriented along the fibre axis, resulting in a high modulus and strength. The fibres are easily stretched in water or steam that is held close to 100°C because the glass transition temperature of the wet acrylic fibre is 75°C.

 

Types of Acrylic Fibres

There are four main types of acrylic fabric:

  1. Acrylic

To be considered normal acrylic fabric, this type of fibre must contain at least 85% pure acrylonitrile. After texturizing, acrylic fibres have a light bulky wool-like hand and overall wool-like aesthetics. The fibres are resilient and possess an excellent acid resistance and sunlight resistance.

  1. Modacrylic

This acrylic fibre variant is composed partially of acrylonitrile, but a variety of other polymers are also used in its production. For instance, modacrylic contains a high degree of vinylidene chloride as such, fabrics made from modacrylic fibre generally have better drapability, wrinkle-resistance, more heat sensitive but more flame resistant and durability than normal acrylic fabrics.

Modacrylic may also resist pilling and abrasion better than acrylic fibre. Modacrylics possess warm wool-like aesthetics and a generally bright luster. Lastly, modacrylic fabrics may hold their shape better than normal acrylic fabrics.

 

  1. Nytril

Unlike acrylic fabric, which is mainly composed of acrylonitrile, nytril is primarily composed of vinylidene dinitrile. Nytril fibres are made up of polymers containing at least 85% vinylidene dinitrile units, which appear at least every other unit in the polymer chain. The comonomer used in Nytril synthesis is vinyl acetate.

While nytril hasn’t been made in the United States since the 1960s, it is still produced in the Asian markets. Since nytril is hard to dye, however, it never became highly popular, and it isn’t produced in large quantities anywhere in the world.

  1. Lastrile

Lastrile is an elastic form of acrylic that is made by mixing a type of chemical called a diene with acrylonitrile and a diene such as butadiene and contain 10%-50% acrylonitrile units. Lastrile fibres have not been commercially produced. This fabric is used in similar applications to acrylic in which greater elasticity is desired.

 

Properties of Acrylic Fibre

Acrylic fibre closely resembles the look and feel of wool fibres and it has properties as follows:

  • Acrylic has a warm and dry hand like wool. Its density is 1.17 g/cc as compared to 1.32 g/cc of wool. It is about 30% bulkier than wool. It has about 20% greater insulating power than wool.
  • Acrylic has a moisture regain of 1.5-2% at 65% RH and 70 deg F.
  • It has a tenacity of 5 gpd in dry state and 4-8 gpd in wet state.
  • Breaking elongation is 15% (both states)
  • It has an elastic recovery of 85% after 4% extension when the load is released immediately.
  • It has a good thermal stability. When exposed to temperatures above 175 deg C for prolonged periods some discolouration takes place.
  • Acrylic shrinks by about 1.5% when treated with boiling water for 30 min.
  • It has a good resistance to mineral acids. The resistance to weak alkalies is fairly good, while hot strong alkalies rapidly attack acrylic.
  • Moths, Mildew and insects do not attack Acrylic.
  • It has an outstanding stability towards commonly bleaching agents.
  • Easy to wash and good dimensional stability.
  • Resistance to damage by moths and chemical substances.
  • Excellent color-fastness and dyeability in brilliant colors.
  • Highly resistant to sunlight.
  • Lightweight, soft, and warm, with a wool-like touch
  • Like polyester and nylon, acrylic fabric is hydrophobic– meaning it repels water. This can lead to bacteria growth in the fabric which may compromise the structure and cause odor.

Dyeing Acrylic Fibres

The variable chemical units in the fibre allowed for fibres of differing dyeing behavior, and some were produced to be dyeable with acid dyes, as wool is.

In the early 2000s, most acrylic fibre variants are dyed with basic (cationic) dyes. Many early synthetic dyes (including Perkin’s Mauve were basic dyes, and these were adopted for acrylics, but dyemakers later developed “modified” basic dyes specifically for use with these fibres. Disperse dyes may also be useful for pale shades. A considerable amount of acrylic and modacrylic fibre is colored during manufacture, either as “solution dyed” fibre or by applying dye to the fibre immediately after spinning in “gel-dyeing.”

The short product life & long landfill life of acrylic fabric

 On its own, acrylic fabric is not resistant to abrasion. Because of this, acrylic fibre is often blended with more resilient fibres to create a more durable product. Acrylic fabric is also highly likely to pill. Needless to say, the product lifespan of acrylic fabric clothing is not considerably long. Then it enters the landfill, where acrylic fabric can last up to 200 years and release toxic chemicals into the environment on its long journey to decomposition. Two hundred years. If you thought that picture of your grandma in the dress with puff sleeves was funny and outdated, just wait until your great-great-great-great-great grandkid finds your Forever21 DayGlo crop top. Because it might still be around! Very pilled, bacteria ridden, and possibly singed. Not to mention, leaching toxins. So if nothing else, wear biodegradable clothing to save face with your heirs.

The Impact on Environment

Since acrylic fabric is not biodegradable, its environmental impact is largely negative. Also, the production processes used to make acrylic fabric harm workers and the ecosystems surrounding manufacturing facilities.

The production processes used to make acrylic fabric are highly volatile, and production plants that manufacture this fibre are constantly at risk of exploding if necessary safeguards fail. A variety of toxic substances are used in the production of acrylic fabric, and if these substances aren’t handled or disposed of correctly, they enter surrounding ecosystems and harm wildlife and human inhabitants. The gases produced in acrylonitrile manufacturing are so harmful that legislation requires they be properly filtered in a closed environment before they can leave a production facility.

Unlike polyester and some other synthetic fabrics, it is practically impossible to recycle acrylic fabric, which means that there is no effective means of disposal of acrylic garments once they are produced. Acrylic fibre is not biodegradable, so it simply accumulates in the environment and will stay there for hundreds of years until it slowly starts to break down.

The tiny fibre fragments produced when consumers wash synthetic fabrics enter the water supply and poison ecosystems. This microfibre crisis is threatening to make water undrinkable in high-density urban areas in which high water consumption and inadequate drinking water filtration techniques result in high concentrations of fibres in the hydrosphere.

For instance, a British scientist recently found that a single load of washed clothes can create up to 700,000 microfibres, and these microfibres then end up on shorelines all over the world. These microfibres simply add to the pandemic crisis of plastics in the oceans.

Additionally, as a volatile organic compound (VOC), acrylonitrile has the potential to create ground ozone, which poisons plants and reduces crop yield. It’s unclear, however, how frequently acrylic fibre production causes this environmentally harmful effect.

Like most other synthetic fibres, acrylonitrile is a fossil fuel derivative. Therefore, production of acrylic fabric furthers human consumption of fossil fuels, and it also takes up fossil fuels that could have been used for vital energy production applications.

Health Risks

In addition to being hazardous to the environment, acrylic fabric may also be hazardous to your health.

Acrylic fibre is made from the polymer polyacrylonitrile. Polyacrylonitrile is a flammable, colorless liquid that is created from polypropylene. The EPA found that inhaling polyacrylonitrile gives the victim similar symptoms to cyanide poisoning. In fact, when exposed to polyacrylonitrile, our bodies metabolize the chemical into cyanide. This metabolization can take place after exposure to the chemical through skin contact, ingestion, or inhalation.

As early as 1979, the U.S. Environmental Protection Agency (EPA) became concerned that residual monomers in acrylic fabric may be carcinogenic. This suspicion has since been substantiated by the U.S. Centers for Disease Control and Prevention; every time your skin comes into contact with acrylic fibres, your chances of developing cancer increase.

On its own, acrylic fabric is highly flammable, which means it must be treated with toxic flame retardants to avoid the possibility of grievously injuring the wearer. The types of flame retardants used are called organophosphates, and these toxic compounds gradually accumulate in the body.

Exposure to synthetic fibres in general during the production process increases breast cancer rates in postmenopausal women. Synthetic fibres like acrylonitrile also serve as breeding grounds for bacteria, which could cause skin conditions and general discomfort.

Uses of Acrylic Fabric

Articles made of acrylic fibres are easy to care for: they dry easily and, if properly set during manufacture, maintain their dimensions. All these properties gave this fibre many uses as follows:

Since acrylic fabric is designed to be similar to wool, it is used in many of the same applications as this highly popular natural fibre. For instance, apparel manufacturers make acrylic fibre into sweaters, mittens, gloves, pants, hoodies, and a variety of other types of cold-weather clothing. Additionally, acrylic is a popular material for carpeting, upholstery, rugs, and other traditionally wool-dominated homeware product categories.

While acrylic is highly similar to wool in its natural state, it can be made to resemble other fabrics, such as cotton, depending on the spinning mechanism that is used. Manufacturers can make types of acrylic that resemble fur, which can be useful for props or costumes.

Acrylic fibre is used as one of the constituents of carbon fibre, which is in high demand in industrial applications. Otherwise, however, acrylic fibre doesn’t have a lot of industrial applications; while this fabric is highly durable, its flammability makes it ineligible for use in many industrial environments.

One of the most prominent applications of acrylic fibre is in knitting. While most people who knit prefer wool for high-end products, many amateur knitters use acrylic as a “learner fibre” or as a yarn for cheap, low-effort projects. While there are significant detractors to using acrylic as a knitting material, its inability to lose its color and inexpensiveness afford it a valuable position within the knitting hobbyist market.

Other apparel uses such as wrinkle resistant fabrics, pile and fleece fabrics, children’s wear.

Outdoor end uses such as car tops, boat covers, awnings, outdoor furniture. Industrial end uses such as filtration materials, reinforcement materials in construction, car batteries

Care of Acrylic Fibre 

Keep in mind that both cold and hot water can be harmful to apparel composed of acrylic fabric. Therefore, you should always wash acrylic clothing with warm water.

When you wash acrylic on cold, it can start to become firm and inflexible, and when you wash this fabric in water that’s too hot, it can melt and damage your washing machine or other items in the load.

Also, acrylic fabric is more prone to pilling than practically any other fabric. If you wash an acrylic garment with garments that don’t closely match its color, you’ll end up with a pierce of apparel covered in pills that are the same color as the garments you washed it with.

Static electricity may be reduced by using a fabric softener in every third or fourth washing. Gently squeeze out water, smooth or shake out garment and let dry on a non-rust hanger. (Sweaters, however, should be dried flat.)

When machine washing, use warm water and add a fabric softener during the final rinse cycle.

Machine dry at a low temperature setting. Remove garments from dryer as soon as tumbling cycle is completed.

If ironing is required, use a moderately warm iron. (For specific instructions, refer to garment’s sewn-in care label.)

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Article by Ms. Hetal Mistry

References :

https://sewport.com/fabrics-directory/acrylic-fabric

https://www.sciencedirect.com/topics/chemistry/acrylic-fibre

https://www.encyclopedia.com/fashion/encyclopedias-almanacs-transcripts-and-maps/acrylic-and-modacrylic-fibres

https://www.aksa.com/en/products/what-is-acrylic-fibre-/what-is-acrylic-fibre-/i-56

https://textilelearner.blogspot.com/2011/03/defination-production-properties-and_5024.html

https://www.textileschool.com/121/acrylic-fibres-manmade-artificial-fibres/

https://www.naturalclothing.com/what-is-acrylic-fabric/