Synthetic Fibres And Plastics
Class VIII Biology
CBSE
Clothes that we wear on a daily basis are made of fabrics. Fabrics are made of fibres which are obtained from natural and artificial sources. fibres like cotton, wool, silk, etc., are obtained from plants or animals. Wool, silk, and cotton are a few examples of natural fibres. The synthetic fibres, on the other hand, are made by human beings. That is why these are called synthetic or man-made fibres . Fibres like polyesters and terylene are a few examples of synthetic fibres.
A synthetic fibre is also a chain of small units joined together. Each small unit is actually a chemical substance. Many such small units combine to form a large single unit called a polymer. The word ‘polymer’ comes from two Greek words; poly meaning many and mer meaning part/unit. So, a polymer is made of many repeating units.
Synthetic fibres and plastics, similar to natural fibres are made up of very large units. The larger units are called polymers. These are made up by combining many similar or dissimilar small units. The small units are called monomers.
Natural fibres are obtained from plant and animal sources, synthetic fibres are obtained by chemical processing of petrochemicals. The synthetic fibres can be woven into a fabric, just like natural fibres.Synthetic fibres have a wide range of uses ranging from many household articles like ropes, buckets, furniture, containers, etc. to highly specialized use in aircrafts, ships, spacecrafts, health care, etc. Depending upon the types of chemicals used for the manufacture, some synthetic fibres are rayon, nylon, polyester and acrylic. A synthetic fibre, as well as plastic, is made up of a chain of small units (called Monomers) which combine to form polymers.
Monomers: A monomer is a single molecule that can bond with other identical molecules to form polymers through a process called Polymerization. Monomer is defined as a simple molecule with two or more binding sites through which it forms covalent linkages with other monomer molecules to form the macromolecule.
Phoebus Levene discovered the monomers of nucleic acids around 1900. Many of the monomers synthesized enzymatically by cells are thought to have originally accumulated spontaneously on Earth as a result of nonenzymatic reactions. These include amino acids, components of proteins and nucleotides, components of nucleic acids (DNA, RNA).
Monomers are thus building blocks of polymers. All simple molecules cannot behave as monomers but only those with two or more bonding sites can act as monomers. Thus molecules like ammonia, water, ethanol etc are not monomers. Alkenes, vinyl chloride, adipic acid, glycol with two bonding sites act as monomers. Monomers and their dimer counterparts are archetypal plasmonic structures and a versatile theory could rightfully be expected to offer new insights for both individual monomers as well as for assemblies of such building blocks.
Polymers: Polymer is a Greek word in which 'poly' means 'many' and 'mer' means units. Hence, polymers are large molecule made up of several molecules (or monomers) linked together. Hermann Staudinger (1881-1965) is known as the founder of polymer chemistry and the father of modern polymer science
polymer, any of a class of natural or synthetic substances composed of very large molecules, called macromolecules, that are multiples of simpler chemical units called monomers. Polymers make up many of the materials in living organisms, including, for example, proteins, cellulose, and nucleic acids. Moreover, they constitute the basis of such minerals as diamond, quartz, and feldspar and such man-made materials as concrete, glass, paper, plastics, and rubbers.
The word polymer designates an unspecified number of monomer units. When the number of monomers is very large, the compound is sometimes called a high polymer. Polymers are not restricted to monomers of the same chemical composition or molecular weight and structure. Some natural polymers are composed of one kind of monomer. Most natural and synthetic polymers, however, are made up of two or more different types of monomers; such polymers are known as copolymers.
Example of Polymers: All synthetic fibers, such as Rayon and Nylon, are polymers. Polymers are also found in Nature. ‘Cotton’ is a polymer called ‘Cellulose’. ‘Cellulose’ is made up of a number of single units (or monomers) called ‘Glucose’. Polymerization Reaction: The process of linking small monomers together to form polymers is called Polymerization.
Natural polymers: organic and inorganic
Organic polymers play a crucial role in living things, providing basic structural materials and participating in vital life processes. For example, the solid parts of all plants are made up of polymers. These include cellulose, lignin, and various resins.
Cellulose is a polysaccharide, a polymer that is composed of sugar molecules. Lignin consists of a complicated three-dimensional network of polymers. Wood resins are polymers of a simple hydrocarbon, isoprene. Another familiar isoprene polymer is rubber.
Other important natural polymers include the proteins, which are polymers of amino acids, and the nucleic acids, which are polymers of nucleotides—complex molecules composed of nitrogen-containing bases, sugars, and phosphoric acid. The nucleic acids carry genetic information in the cell. Starches, important sources of food energy derived from plants, are natural polymers composed of glucose.
Many inorganic polymers also are found in nature, including diamond and graphite. Both are composed of carbon. In diamond, carbon atoms are linked in a three-dimensional network that gives the material its hardness. In graphite, used as a lubricant and in pencil “leads,” the carbon atoms link in planes that can slide across one another.
Rayon You have read in Class VII that silk fibre obtained from silkworm was discovered in China and was kept as a closely guarded secret for a long time. Fabric obtained from silk fibre was very costly. But its beautiful texture fascinated everybody. Attempts were made to make silk artificially. Towards the end of the nineteenth century, scientists were successful in obtaining a fibre having properties similar to that of silk. Such a fibre was obtained by chemical treatment of wood pulp. This fibre was called rayon or artificial silk.
Although rayon is obtained from a natural source, wood pulp, yet it is a man-made fibre. It is cheaper than silk and can be woven like silk fibres. It can also be dyed in a wide variety of colours. Rayon is mixed with cotton to make bed sheets or mixed with wool to make carpets.
Rayon is a versatile fibre and can imitate the feel and texture of silk, wool, cotton and linen with drape and slipperiness akin to nylon. Rayon, invented in 1846, began to be manufactured in the United States in 1911. Called artificial silk until 1924 when the name rayon was coined, rayon was a less expensive alternative to silk clothing and accessories. This paper focused on the time period of 1910-1924.
In the 1860s, the silk fiber industry in France was in trouble, leading to a demand for regenerated fiber. Count Hilaire de Chardonnet addressed this issue by inventing artificial silk from cellulosic material and obtaining a patent in 1885. The term “rayon” was actually coined by the Federal Trade Commission (FTC), and by 1925, rayon production was in full swing. Rayon fiber is now a very popular fiber because it closely resembles natural materials like cotton and silk. People value rayon for its breathability and its capacity to absorb moisture.
Rayon fiber comes from natural cellulose sources. It has the ability to mimic the tactile sensations and fabric textures of silk, wool, cotton, and linen. Traditional viscose rayons are less durable and tend to lose their appearance, especially when wet. The flexibility of lyocell rayon fabric affects its ability to resist excessive shrinking or looseness in clothing.
These fibers easily take on a wide range of dye colors. Rayon fibers vary in denier, with measurements spanning from 1.5 to 15. Rayon has the least elastic recovery of any fiber. Rayon fiber naturally has a shiny appearance. Rayon fiber is valued for its softness, comfort, and versatility. When wet, rayon temporarily weakens. Rayon fiber are extremely soft, smooth, cool, and very absorbent, though they may not always provide warmth.
This is a type of synthetic fibre obtained from wood pulp. Rayon is soft, absorbent and comfortable. It is easy to dye in wide range of colors. Rayon is mixed with cotton to make bedsheets. Rayon is mixed with wool to make carpets. t is a man-made fibre obtained from a natural source called wood pulp. It can be dyed in a wide variety of colours. Rayon is mixed with cotton to make bedsheets or mixed with wool to make carpets. Rayon resembles silk in appearance, texture and shine. Hence, it is also known as Artificial Silk. Silk fibre was discovered in China and made from silkworms. It had a beautiful texture and was very costly. By the end of the 19th century, scientists managed to make an artificial silk-like fibre made by treating wood pulp chemically.
This man-made fibre uses natural material (wood pulp) and can be woven like silk fibre. It is cheaper than silk and can be dyed in a variety of colours. It can be: Make apparels like suits, slacks, jackets etc. Make automobile tyre cords (because of its strength) Mixed with cotton to make bedsheets and bedspreads Mixed with wool to make carpets and blankets Used to make other home furnishings, such as curtains and tablecloths.
Breezy Clothing: Rayon’s natural drape is perfect for creating light and breathable garments like loose tops and bottoms.
Sporty Styles: Rayon’s moisture-wicking and breathability properties make it a popular option for athletic wear, ensuring you remain cool and dry during exercise.
Chic Outfits: Rayon’s smooth, shiny texture, cost-effectiveness, and low maintenance have made it a top choice to replace natural silk in various clothing items, from blouses to lingerie.
It’s budget-friendly. It breathes easily, similar to cotton fiber. It mixes well with different fibers, especially woven fabrics. Many appreciate its silk-like texture. It’s a great option for people who want a luxurious appearance without spending too much. It can be dyed with ease, resulting in vivid, stunning colors. It gracefully hangs and drapes well.
It readily absorbs moisture, body oils, and water, potentially causing stains. It tends to stretch and sag without recovering well. Its production harms the environment, making it unsustainable despite coming from wood. Treating stains may lead to permanent marks. The fabric is fragile, especially when wet. Dry cleaning is the recommended cleaning method. It’s not suitable for home furnishings due to its tendency to stretch.
Nylon fiber is a family of synthetic polymers, made up of repeating units linked by amide bonds. This material is versatile, as it’s a thermoplastic with a smooth, silky texture, allowing it to be melted and shaped into fibers, films, or different forms. Nylon polymers often include various additives to give them a wide range of properties. Nylon polymers are crucial in making fabrics. They are also important in various types of textile fibers, like those used in clothing, flooring, and strengthening rubber. Additionally, nylon fiber is molded into various shapes for applications such as making automotive parts and electrical equipment.
Nylon is another man-made fibre. In 1931, it was made without using any natural raw material (from plant or animal). It was prepared from coal, water and air. It was the first fully synthetic fibre. Nylon fibre was strong, elastic and light. It was lustrous and easy to wash. So, it became very popular for making clothes. Nylon is very lustrous, easy to wash and elastic. It dries quickly and retains its shape.
We use many articles made from nylon, such as socks, ropes, tents, toothbrushes, car seat belts, sleeping bags, curtains, etc. Nylon is also used for making parachutes and ropes for rock climbing. A nylon thread is actually stronger than a steel wire.
Apparel: High-tenacity nylons have a range of applications in the clothing industry. They are used to make parachute fabrics, cords, and ropes. These nylons are valued for their excellent dimensional stability, making them a great choice for producing items like women’s gloves, hosiery, underwear, swimwear, stockings, and hosiery fabrics.
Household: Nylon is a popular material for various household items, such as carpets and upholstery. It is also employed in the construction of ropes and cords for various domestic purposes.
Industrial Applications: Nylon plays a vital role in industrial settings, with uses in finishing nets, tire cords, filtering cloths, sewing threads, and tow ropes. It is also used in the production of belts for various types of machinery, including flat belts and V-belts.
There are eight types of nylon fiber, such as Nylon 6, Nylon 6,6, Nylon 4,6, Nylon 6,9, Nylon 6,10, Nylon 6,12, Nylon 11, and Nylon 12. Here are a few examples: Nylon 6, developed by Paul Schlack, is made using a ring-opening polymerization method.
Tenacity: Dry strength ranges from 4 to 9 gm/den, with wet strength reaching 90% of the dry strength.
Elasticity: Typically stretches by 20-40% before reaching the breaking point. Stiffness: Falls within the range of 20 to 40 gm/den. Moisture regains: Approximately 3.5-5%, although it’s not highly absorbent due to its crystalline structure. Specific gravity: Around 1.14. Abrasion resistance: Demonstrates excellent durability against wear and tear. Dimensional stability: Shows good resistance to changes in shape or size. Resiliency: Exhibits an excellent ability to bounce back. Softening point: Nylon 6,6 softens at 229°C, while Nylon 6 softens at 149°C. Melting point: Nylon 6,6 has a melting point of 252°C, whereas Nylon 6 melts at 215°C.Hand feel: Known for its soft and smooth texture.
Acid: Nylon 6,6 is highly vulnerable to mineral acids and can dissolve when exposed to them. However, it remains unreactive to dilute acetic and formic acids, even when heated. Concentrated formic acid can dissolve Nylon 6,6. Nylon 6 is also sensitive to mineral acids but can withstand mild boiling organic acids.
Bleaches: Nylon fiber is generally resistant to damage from both oxidizing and reducing bleaches, but it may be negatively impacted by chlorine and strong oxidizing bleaches. Alkali: Nylon is notably resistant to alkalis. Organic Solvent: Most solvents have little to no effect on nylon. However, phenol, metacresol, and formic acid can dissolve the fiber. Fortunately, the solvents commonly used for stain removal and dry cleaning do not harm it. Light: Nylon does not change color when exposed to light. Nonetheless, Nylon 6 gradually loses strength when exposed to prolonged light. Biological: Nylon is not susceptible to damage from microorganisms or moth larvae. Electrical: Nylon has high insulating properties, which can result in the accumulation of static charges on the fiber. Flammability: Nylon burns slowly.
Strength: Nylon possesses exceptional tensile strength, making it a prime choice for applications like ropes, gears, and machinery components. Its robust resistance to abrasion also renders it well-suited for situations where wear and tear are a concern.
Versatility: Nylon fiber can take on various forms, including fibers, films, and moldings. Its ease of color customization proves advantageous for products that necessitate consistent coloration, like clothing and textiles.
Durability: Nylon’s remarkable resistance to wear and tear makes it an outstanding option for products subjected to frequent and prolonged use. This durability is especially valuable for applications that require enduring performance, such as gears, ropes, and backpacks.
Moisture Resistance: Nylon exhibits impressive resistance to moisture, making it a perfect choice for products exposed to water or other liquids. It is frequently utilized in outdoor gear, clothing, and applications that prioritize hygiene, such as medical devices and packaging.
Chemical Resistance: Nylon can withstand a broad array of chemicals, including acids and bases. This property finds utility in laboratory equipment and industrial products.
Lightweight: Nylon’s lightweight nature is pivotal for reducing weight in applications such as aircraft and automotive parts, as well as gear, ropes, and backpacks.
Ease of Processing: Nylon is easily processed and can be molded into intricate shapes and designs. This characteristic diminishes the need for additional machining or assembly processes, resulting in a cost-effective solution.
Cost: Nylon can be more expensive than other synthetic materials like acetate, acrylic, lyocell, microfiber, and similar options.
Hydrolysis: Nylon is vulnerable to hydrolysis, a chemical reaction that causes it to deteriorate in the presence of moisture. This degradation can lead to a decrease in nylon’s strength and durability over time, making it less suitable for long-term applications or use in moist environments.
UV Sensitivity: Nylon is sensitive to ultraviolet (UV) light and may degrade when exposed to sunlight. This makes it a less ideal choice for outdoor applications.
Limited Temperature Resistance: Nylon has restricted resistance to high temperatures, and it may deform or lose strength when exposed to heat. Therefore, it’s not the best option for high-heat applications, such as electrical insulation.
Flammability: Nylon is a flammable material and can catch fire easily. For safety reasons, consider alternative materials that are less prone to ignition.
Environmental Impact: Nylon fiber production consumes a significant amount of energy and can have detrimental effects on the environment. It also contributes to the accumulation of plastic waste in natural surroundings.
Polyester: Polyester is another synthetic fibre. Fabric made from this fibre does not get wrinkled easily. It remains crisp and is easy to wash. So, it is quite suitable for making dress material. You must have seen people wearing polyester shirts and other dresses.
Terylene is a popular polyester. It can be drawn into very fine PET is a very familiar form of polyester. It is used for making bottles, utensils, films, wires and many other useful products.
Polyester (Poly+ester) is actually made up of the repeating units of a chemical called an ester. Esters are the chemicals which give fruits their smell. Fabrics are sold by names like polycot, polywool, terrycot, etc. As the name suggests, these are made by mixing two types of fibres. Polycot is a mixture of polyester and cotton. Polywool is a mixture of polyester and wool. PET (polyethene terephthalate) is used for making bottles, utensils, films, wires and many other useful products.
To understand the history of polyester fabric, you must take a step back to the creation of polyester plastic. The first research into polyester plastic began in 1926. Polyester was invented in the mid-1930s by W.H. Carothers along with his team while working at DuPont. However, this work was not further developed until 1941 when it was expanded upon and patented by a group of British scientists who created the first polyester fiber.
Some of the other inventions and developments that impacted modern polyester include:
The resin that binds polyester has dramatically improved in the last 50 years. The higher quality resin creates smaller seams which irritate sensitive skin less. Resin is one of the most valuable developments, and this technology is a closely guarded trade secret. Companies began adding different polyester additives that changed the fabric’s color and appearance. The additives made polyester retain its color, hang more naturally, and make it less shiny.
The development of microfiber was a game changer. Microfibers are much smaller than traditional polyester fabric fibers (about 1/100 the size of a human hair). Microfibers make modern clothing of this fabric more comfortable. The ability to crimp, stretch, and change the shape of polyester fibers also significantly impacted the popularity, feel, and quality of the clothing. Polyester is now one of the most popular fabrics in the world. Companies use polyester to make clothing, furniture, carpets, tires, and insulation.
Polyester fabric has many characteristics and properties that make it useful in the modern world. Polyester is wrinkle-resistant, easy to care for, and often blended with other fibers to create a more durable material.
Fabric Breathability: Polyester is a breathable fabric and often gets blended with cotton or other materials to improve its breathability. Polyester and cotton blends are some of the most popular in the world and combinates the comfort of cotton with the quick drying nature of polyester.
Moisture-Wicking Abilities: Polyester is one of the best fabrics you can find if you require a moisture-wicking material. This synthetic material moves moisture away from the body, keeping you dry. It’s also breathable, lightweight, and shows durability. You’ll find that outdoor clothing typically contains polyester for this reason.
Heat Retentin Abilities: Unfortunately, since you make polyester with petroleum, it means that polyester is flammable, and the fabric will melt if it comes into contact with a flame. As a result, drying polyester fabrics at high temperatures can permanently damage the fabric.
Stretchiness: Since polyester fibers are artificial, they contain no elasticity. So, 100% polyester yarns will usually not have any stretchiness. However, textile experts have discovered that new weaving methods can incorporate a bit of stretch into the fabric, and you’ll find that polyester blends usually have some stretch characteristics.
Pilling/Bubbling: Polyester is susceptible to pilling, which is when small balls of fabric form on the fabric’s surface. Pilling happens when materials rub against each other and when you wash a garment. Once pilling begins on a polyester fabric, the damage is permanent.
There are two types of polyester: Polyethylene Terephthalate (PET or PETE), Polybutylene Terephthalate (PBT) PBT is a type of polyester that you make from Polybutylene Terephthalate. PBT is a less common polyester type, but it is sometimes used instead of PET because it has a higher melting point.
In addition to PET and PBT, polyester comes in several different forms. The four most common forms of polyester are filament, tow, staple, and fiberfill. A polyester filament is a single long strand most frequently used to produce clothing. Polyester staples are shorter pieces of filament cut at predetermined lengths. Industry leaders commonly use polyester staples when blending polyester with other fabrics.
Multiple filaments comprise a tow of polyester. The filaments are close together but still leave space for additional fabric. Finally, fiberfill is a type of polyester that has the most volume. It helps produce insulation, pillows, and cold-weather clothing. It can take the place of materials like goose down. The fluffiness of fiberfill makes it an excellent insulator. Of the four types of polyester, filament and staple are the two most common types.
The advantages of polyester have many benefits, making it a popular choice for fabric. It is wrinkle-resistant and has a high resistance to tearing. Polyester is also easy to care for, as it can be washed in the machine and does not require ironing. Polyester is also a budget-friendly fabric option. Polyester is often used in sportswear and active wear because it is lightweight and breathable. The fabric is also a popular choice for making blankets and bedding sheets, as it is warm and cozy. Another advantage of polyester is that it is static-resistant. Companies use polyester to make clothing for people who work in environments prone to static electricity, such as laboratories and cleanrooms.
There are several disadvantages of polyester as well. Polyester is not as absorbent as natural fibers, so it can feel sweaty and uncomfortable to wear in hot weather. Polyester is also not a good choice for people with allergies, as it can cause skin irritation. One of the most significant disadvantages of polyester is that it is not biodegradable, so it can cause environmental pollution. It is not biodegradable because you make it out of petroleum.
Acrylic: Acrylic is artificial wool. We wear sweaters and use shawls or blankets in the winter. Many of these are actually not made from natural wool, though they appear to resemble wool. These are prepared from another type of synthetic fibre called acrylic. The wool obtained from natural sources is quite expensive, whereas clothes made from acrylic are relatively cheap. They are available in a variety of colours.
Synthetic fibres are more durable and affordable which makes them more popular than natural fibres. You have already performed an activity of burning natural and synthetic fibres (Activity 3.6 of Class VII). What did you observe? When you burn synthetic fibres you find that their behaviour is different from that of the natural fibres. You must have noticed that synthetic fibres melt on heating.
This is actually a disadvantage of synthetic fibres. If the clothes catch fire, it can be disastrous. The fabric melts and sticks to the body of the person wearing it. We should, therefore, not wear synthetic clothes while working in in the kitchen or in a laboratory. Acrylic fiber is made from synthetic plastic. It comes from man-made polymer textile fibers created using chemicals from fossil fuels. Making acrylic fiber is similar to making polyamide, nylon fibers, and polyester fibers.
Acrylic was developed in Germany in 1893 to mimic wool. In 1950, the E.I. Dupont Company introduced it in the U.S. By 1991, it was popular for wash-and-wear items like sweaters and blankets. Acrylic fibers are made using wet and dry spinning methods, with the latter being more common. Care labels are important when handling acrylic, as it has unique characteristics. Acrylic is similar to wool fibers but has some differences. It gets crimped during dry spinning, providing warmth without extra weight. It’s a cost-effective alternative to wool, favored by consumers for its affordability and availability.
In the market, you can find four main types of acrylic fabrics: Acrylic: Regular acrylic fiber, made of at least 85% pure acrylonitrile. Produced through wet or dry spinning methods. Texturized to give it a light, bulky, wool-like texture. Resistant to both acid and sunlight.
Modacrylic: A variant of acrylic fiber, featuring a composition that includes acrylonitrile and a significant amount of vinylidene chloride. Offers a warm, pleasant feel with enhanced drivability, resiliency, and wrinkle resistance. Provides better resistance to pilling, flames, and abrasion compared to acrylic fabric. Excels in maintaining its shape, resisting wrinkles, and retaining creases. Often used in specialty applications.
Nytril: Unlike other acrylic variants relying on acrylonitrile, Nytril is primarily composed of vinylidene dinitrile. Produced from polymers containing at least 85% vinylidene dinitrile units and a vinyl acetate co-monomer. More popular in the Asian market than in the United States. It can be challenging to dye, and global production quantities are relatively small.
Lastrile: Lastrile fibers are formed by blending copolymers of acrylonitrile and diene, such as butadiene. These fibers contain 10%-50% acrylonitrile units and are known for their elasticity. They are used in applications requiring greater elasticity in acrylic fibers. However, Lastrile fibers have not been widely produced for commercial use.
Acrylic fibers resist many chemicals, including acids, alkaline solutions, bleaches, and oxidizing agents. They can take sudden impacts without breaking because they have strong impact resistance. Acrylic fibers don’t easily absorb moisture due to their hydrophobic nature, but they can hold on to atmospheric moisture. They are durable, with excellent fatigue resistance that allows them to withstand repeated loads.
Acrylic fibers can handle high temperatures from 160-250°C without melting.They don’t easily degrade or fade when exposed to sunlight, making them UV resistant. While they may slowly deform under constant load or stress due to low creep resistance. Acrylic fibers don’t dissolve in water or most organic solvents. They are flammable and can melt and drip when exposed to heat, but they self-extinguish when the heat source is removed.
They also resist mildew and other microorganisms. Acrylic fibers are strong and can endure bending and twisting without breaking. They also have moderate to good abrasion resistance against wear and tear. By making chemical modifications, acrylic fibers can be customized to enhance specific properties or create different types of acrylic fibers.
It’s lightweight. It’s impressively durable. The fabric has exceptional elasticity, quickly returning to its original shape after stretching. It feels gentle to the touch. It keeps the wearer warm. It exhibits remarkable resistance to sunlight and weathering. It can be washed, depending on the fabric type and finish.
It can stretch and shrink easily. It has moderate strength. Because it repels moisture, it may cause static electricity and pilling. It degrades and changes color when exposed to extreme heat.
Apparel includes sweaters, socks, fleece clothing, circular-knit garments, sportswear, and children’s wear. Household textiles consist of carpets, blankets, area rugs, upholstery, and pile fabrics. Outdoor uses involve car tops, boat covers, awnings, and outdoor furniture. Industrial applications include filtration materials, construction reinforcement, and components for automotive batteries.
Plastics is the term commonly used to describe a wide range of synthetic or semi-synthetic materials that are used in a huge and growing range of applications. Plastic is defined as a material that contains an essential ingredient an organic substance of large molecular weight. It is also defined as polymers of long carbon chains. Carbon atoms are linked in chains and are produced in long-chain molecules.
Plastic was discovered by famous German chemist Christian Schonbein in 1846. Plastics were actually discovered accidentally. Christian was experimenting in his kitchen and by accident, he spilt a mixture of nitric acid and sulphuric acid. To mop that solution (a mixture of nitric and sulphuric acid) he took a cloth and after moping he kept it over the stove. After some time, the cloth disappeared and from their plastic got its name.
The word, plastic, was derived from the word ‘Plastikos’ meaning ‘to mould’ in Greek. Fossil fuels have compounds containing hydrogen and carbon (hydrocarbon) which act as building blocks for long polymer molecules. These building blocks are known as monomers, they link together to form long carbon chains called polymers.
The 20th century saw a revolution in plastic production: the advent of entirely synthetic plastics. Plastics originated from natural polymers like cellulose but were transformed through human innovation using synthetic polymers made from fossil fuels. The first synthetic plastic, celluloid, was invented in 1869 as an ivory substitute.
Later plastics like Bakelite provided more possibilities. After World War II, plastic production and usage increased dramatically. While initially seen as positive, plastics are now a major source of environmental waste and potential health concerns due to chemicals used in production. Scientists are working on more sustainable bioplastics and improved recycling to address these issues and ensure plastics have a place in the future.
You must be familiar with many plastic articles used everyday. Make a list of such items and their uses. Plastic is also a polymer like the synthetic fibre. All plastics do not have the same type of arrangement of units. In some it is linear, whereas in others it is cross-linked.. Plastic articles are available in all possible shapes and sizes as you can see in market.
Have you ever wondered how this is possible? The fact is that plastic is easily mouldable i.e. can be shaped in any form. Plastic can be recycled, reused, coloured, melted, rolled into sheets or made into wires. That is why it finds such a variety of uses. Polythene (Poly+ethene) is an example of a plastic. It is used for making commonly used polythene bags. Now, try to bend a piece of plastic yourself. Depending on physical properties, plastics are divided into two types: Thermoplastic and thermosetting.
Thermoplastic: Can all the plastic articles be bent easily? You will observe that some plastic articles can bend easily while some break when forced to bend. When we add hot water to a plastic bottle, it gets deformed. Such plastic which gets deformed easily on heating and can be bent easily are known as thermoplastics. Polythene and PVC are some of the examples of thermoplastics. These are used for manufacturing toys, combs and various types of containers.
Thermosetting: On the other hand, there are some plastics which when moulded once, can not be softened by heating. These are called thermosetting plastics. Two examples are bakelite and melamine. Bakelite is a poor conductor of heat and electricity. It is used for making electrical switches, handles of various utensils, etc. Melamine is a versatile material. It resists fire and can tolerate heat better than other plastics. It is used for making floor tiles, kitchenware and fabrics which resist fire.
Plastics have a few unique properties that make them practical for a wide range of applications. Plastic materials are regarded as: Usually lightweight with a high strength-to-weight ratio. Very versatile. Moldable into different shapes and sizes. Thermally and electrically insulating. Inexpensive. Resistant to chemicals. Very durable.
Non-biodegradable. Usually clear and can be colored in different hues. Different textures are possible. Plastic can come in many different colors and textures, depending on the type of plastic and how it has been treated or processed. Plastic is a synthetic polymer made from various organic materials that can be molded into almost any shape.
Some types of plastic are clear and transparent, like those used in disposable water bottles, while others are opaque and available in a range of colors. Plastic can also have different surface textures, ranging from smooth and shiny to rough and matte. Some types of plastic have soft and flexible textures, while others are rigid.
Plastics can have a wide range of physical and chemical properties, depending on their chemical structures and how they are processed. However, some general physical and chemical properties are common to most plastics. These properties are given below:
Density: Plastics come in many different densities, from as low as 0.9 g/cm³ for foamed plastics to as high as 1.5 g/cm³ for some engineering plastics. Melting Point: The melting points of plastics vary widely depending on the type of polymer. Some plastics have low melting points and can be easily molded while others have high melting points and require specialized processing techniques. Hardness: Plastics can range from soft and flexible to hard and rigid, depending on the specific polymer and its processing.
Transparency: Some plastics are optically transparent while others are opaque and block light. Many transparent plastics can accept dye if you need them to be opaque. Permeability: Plastics can be permeable to gasses and liquids, which can be an advantage in some applications (such as food packaging) and a disadvantage in others (such as chemical storage).
Resistance to Chemicals: Many types of plastic are resistant to industrial chemicals, acids, and other corrosive substances. This makes them useful in a variety of industrial applications.
Stability: Some plastics are sensitive to heat, light, and radiation, which can cause them to degrade over time. UV stabilizers and antioxidants are often added to plastics to improve their stability.
Flammability: Plastics can be highly flammable, and many of them release toxic gasses when burned. Flame retardants are often added to plastics to improve their fire resistance.
Degradation: The rate at which plastics degrade depends on a variety of factors, including the type of plastic, the conditions to which they are exposed, and the specific environmental factors they encounter. Some plastics, such as polyethylene (PE) and polypropylene (PP), degrade very slowly so they will persist in the environment for hundreds of years. Other plastics, such as polylactic acid (PLA), are designed to be biodegradable and can break down much more quickly when exposed to moisture, heat, or microorganisms. Some plastics can undergo physical degradation, such as cracking or fragmentation, even if they do not break down chemically. This can be caused by sunlight, temperature changes, or mechanical stress, and can lead to the release of hazardous plastic particles called microplastics into the environment.
Solubility: Each plastic has unique solubility characteristics. Plastics that are amorphous (not crystalline), like polystyrene and polycarbonate, are more soluble in typical organic solvents than crystalline ones. Certain highly crystalline polymers, including nylon and polyolefin, resist dissolution while others like polyvinyl acetate (PVA) are highly soluble in water.
Reactivity: Plastics can be reactive in different ways, depending on their chemical composition. For example, polyethylene reacts with oxygen to form carbon dioxide and water while polypropylene is relatively unreactive and stable in most chemical environments.
Biodegradability: Some plastics, such as polyethylene, are not biodegradable and can persist in the environment for hundreds of years. Others, such as polycaprolactone (PCL), are biodegradable and can be broken down by bacteria and fungi over time.
Recyclability: Plastics can be difficult to recycle since they each have different chemical compositions and properties. Some types of plastics are easier to recycle than others, and recycling methods vary depending on the type of plastic. Recycling of plastic is very important. If they are not recycled at the proper time, then they get mixed with other chemicals or materials and hence become more difficult to recycle and become a source of pollution.
You know that metals like iron get rusted when left exposed to moisture and air. But plastics do not react with water and air. They are not corroded easily. That is why they are used to store various kinds of material, including many chemicals.
Uses of Plastic: Key Industries That Use It: Plastic has many different applications and we see engineers from many industries quoting plastic parts with Xometry. Some of the most common uses of plastic we have seen are listed below:
Plastics are used in various parts of automobiles, including dashboards, bumpers, engine parts, and interior panels. Since they’re both lightweight and durable, they reduce the vehicle’s weight and improve fuel efficiency.
Medical Devices Plastic is an ideal material to use for product packaging. Plastics are adaptable, hygienic, light, flexible, and durable. Packaging is thus responsible for the majority of the plastics used globally, coming in the form of vending packaging, baby products, protective packaging, containers, bottles, drums, trays, boxes, cups, and much more. Plastics are used extensively in the medical industry, including, but not limited to, disposable syringes, IV and blood bags, prosthetic limbs, implantable devices, dialysis machines, heart valves, tubing, and wound dressing. Medical-grade plastics are sterile and biocompatible and can be easily molded into complex shapes. Plus, they’re often less expensive than traditional medical materials.
Plastics are often used in the production of toys because they can be molded into various shapes and colors. Plastic toys are durable and lightweight, so they withstand wear and tear.
Plastics are non-conductive, meaning they can protect electronic components and allow for easy assembly. This is why you find plastic in computer and phone cases and as the insulation on wires.
Plastics are highly durable, lightweight and, most significantly, can be moulded into any form or shape. These properties are a few reasons for the use of plastics. Plastics are extremely versatile materials that can be useful for a wide range of applications. The potential to be moulded makes plastic ideal packaging material. Plastics in packaging help keep food healthy and fresh. As durable and lightweight, plastics have helped in the field of electronics. From computers and cell phones to TV and refrigerator, nearly all of the appliances around us use plastic. Plastics help in making safety gears such as helmets, goggles, etc.
Plastics are also useful in the construction sector because of their low maintenance and high durability. Because of plastic’s strength and it’s lightweight properties, it is useful in making toys, electrical switches and other household goods. As it is non-reactive to air and water, they help store water in plastic bottles and chemicals in chemical laboratories. Plastic is a weak conductor of electricity and heat, so its insulation properties help in the coating of electrical wire and various household products like utensils handles, etc.
You have learnt above that plastics are poor conductors of heat and electricity. That is why electrical wires have plastic covering, and handles of screw drivers are made of plastic. As mentioned above, handles of frying pans are also made of plastic.
When we go to the market, we usually get things wrapped in plastic or packed in polythene bags. That is one reason why plastic waste keeps getting accumulated in our homes. Ultimately, plastic finds its way to the garbage. Disposal of plastic is a major problem. Why? A material which gets decomposed through natural processes, such as action by bacteria, is called biodegradable. A material which is not easily decomposed by natural processes is termed non-biodegradable. Since plastic takes several years to decompose, it is not environment friendly. It causes environmental pollution. Besides, the burning process in the synthetic material is quite slow and it does not get completely burnt easily. In the process it releases lots of poisonous fumes into the atmosphere causing air pollution.
How can this problem be solved?
Have you ever seen a garbage dump where animals, especially cows, are eating garbage? In the process of eating the food waste they swallow materials like polythene bags and wrappers of food. Can you imagine the consequences? The plastic material chokes the respiratory system of these animals, or forms a lining in their stomachs and can be the cause of their death. The polybags carelessly thrown here and there are responsible for clogging the drains, too. Sometimes we are very careless and throw the wrappers of chips, biscuits and other eatables on the road or in parks or picnic places. Should we not think twice before doing so ? As a responsible citizen what measures do you suggest to keep public places clean and free of plastic?
Avoid the use of plastics as far as possible. Make use of bags made of cotton or jute when you go for shopping. The biodegradable and nonbiodegradable wastes should be collected separately and disposed off separately. Practise this in your homes. It is better to recycle plastic waste. Most of the thermoplastics can be recycled. Make a list of items that can be recycled.
However, during recycling certain colouring agents are added. This limits its usage especially for storage of food. As a responsible citizen remember the 4 R principle. Reduce, Reuse, Recycle and Recover. Develop habits which are environment friendly.
Thank You
