Synthetic Fibres and Plastics - Class 8 Notes & Olympiad Questions

Synthetic Fibres and Plastics - Class 8 Science

  • Fibres and Fabrics
  • Types of Synthetic Fibres
  • Plastics
  • Solved Questions on Synthetic Fibres and Plastics
  • Fibres and Fabrics

    Fabric is created from fibres, which are thin and thread-like materials. Based on their source of origin, fibres can be classified into two main categories: natural fibres and synthetic fibres.

    Natural Fibers: These fibres are obtained directly from nature, either from plants or animals. Some examples of natural fibres include cotton, which comes from cotton plants; wool, obtained from sheep; and silk, derived from silkworms. These fibres have been used for a very long time to make various items, especially clothing.

    Synthetic Fibers: Unlike natural fibres, synthetic fibres are man-made. They are created through several processes using raw materials derived from petroleum, known as petrochemicals. Examples of synthetic fibres include nylon and polyester. These fibres were developed to have specific properties and characteristics, such as strength, elasticity, and resistance to water.

    Both synthetic fibres and plastics have a similar structure. They consist of a chain of small chemical units called monomers, which are linked together to form a large molecule called a polymer.

    Interestingly, polymers can also exist naturally. An example is cellulose, a natural polymer made up of many glucose units. Cotton, one of the natural fibres, is predominantly composed of cellulose.

    Types of Synthetic Fibres

    1. Rayon

    a) Rayon is a type of synthetic fibre that is made from wood pulp, which is a naturally occurring cellulose material found in plants.
    b) Due to its resemblance to silk in appearance and texture, rayon is often referred to as "artificial silk." However, it is more durable than silk, making it a popular choice for various applications.
    c) Rayon is commonly used to make dress materials, giving them a luxurious and silky feel without the high cost of natural silk. Additionally, its durability makes it suitable for producing carpets. Moreover, rayon is also used in making tyre cords, which are an essential component in the manufacturing of sturdy and reliable vehicle tires.
    d) Rayon's versatility and similarity to silk make it a sought-after synthetic fibre in the textile and industrial industries, allowing us to enjoy the benefits of silk-like fabrics without compromising on durability and affordability.

    2. Nylon

    a) Nylon is one of the earliest and most significant synthetic fibres, entirely made from chemicals rather than being sourced from plants or animals.
    b) It is created using raw materials derived from coal, air, and water through a complex chemical process.
    c) Nylon is highly renowned for its exceptional properties. It is incredibly strong, making it ideal for applications that require durability and resilience. Its elasticity allows it to stretch without breaking, which is essential for items like parachutes and hosiery goods, providing strength and flexibility in these products.
    d) Another advantageous characteristic of nylon is its lightweight nature. This property makes it perfect for use in lightweight clothing and accessories. Additionally, its wrinkle-resistant quality ensures that garments made from Nylon remain relatively smooth and unwrinkled, even after extended use.
    e) One remarkable feature of nylon is its ability to absorb very little water. This makes it a preferred choice for items that need to stay dry and maintain their shape, even in damp or humid conditions. For example, nylon is commonly used in making umbrellas and raincoats, providing excellent water resistance.
    f) Due to its wide array of favourable properties, nylon finds numerous applications in various industries. Besides parachutes, hosiery goods, and rainwear, nylon is also used to make dress materials, paintbrushes, and a variety of other products. Its versatility and strength make it a valuable material in modern textile and industrial manufacturing.

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    3. Polyester

    a) Polyester is a synthetic fibre that is derived from a specific type of chemical unit called "ester." It is manufactured from petroleum, which is a type of fossil fuel found deep underground.
    b) Polyester is well-known for its impressive properties that make it highly versatile and widely used in various applications.
    c) One of the key characteristics of polyester is its water resistance. It does not easily absorb water, making it suitable for items that need to stay dry, such as outdoor clothing, raincoats, and umbrellas.
    d) Additionally, polyester is incredibly strong and tough, providing durability to the products made from it. This strength makes it a preferred choice for items that undergo regular wear and tear, like backpacks and sportswear.
    e) Another advantageous property of polyester is its crease resistance. Clothes made from polyester tend to stay relatively smooth and wrinkle-free, even after being folded or packed, making them easy to maintain and wear without the need for ironing.
    f) Polyester can also be blended with other fibres to create unique fabrics with combined properties. For example, polywool is a blend of polyester and wool, while polycot is a blend of polyester and cotton. Terrycot, on the other hand, is a blend of terylene (another name for polyester) and cotton. These blends offer a combination of the benefits of both fibres.
    g) Due to its versatility, polyester is widely used to make various dress materials, ranging from casual wear to formal attire. It is a popular choice in the fashion industry due to its wide range of colours, patterns, and textures.
    h) Moreover, one specific type of polyester called polyethylene terephthalate (P.E.T.) is commonly used for making wires, films, bottles, and utensils. P.E.T. bottles, in particular, are widely used for packaging beverages and other liquids due to their lightweight and non-breakable nature.
    i) Overall, polyester's outstanding properties, bendability, and affordability make it a favoured material in the textile industry and beyond, playing a crucial role in various everyday products and applications.

    4. Acrylic

    a) Acrylic is a synthetic fibre that bears a striking resemblance to wool in terms of its appearance and texture. It is a popular choice for various applications due to its advantageous properties.
    b) One of the notable characteristics of acrylic is it's lightweight, making it comfortable to wear without feeling heavy or cumbersome. It is also exceptionally soft and warm, providing a cosy feel similar to natural wool.
    c) An important benefit of acrylic is its resistance to wrinkles, allowing garments made from this fibre to maintain their smooth and neat appearance even after extended use or storage. Additionally, acrylic does not easily shrink, which is a desirable quality for clothing that needs to retain its original size and shape.
    d) Acrylic is also favoured for its affordability, as it is a more budget-friendly alternative to natural wool. This makes it accessible to a broader range of consumers who seek warmth and comfort without exceeding their budget.
    e) Moreover, acrylic is resistant to moths and insects, making it a durable choice for clothing items that need protection from these pests.
    f) Due to its excellent properties, acrylic is widely used in making various cold-weather essentials like blankets, shawls, and sweaters. Its warmth, softness, and resistance to wrinkles and shrinking make it an excellent option for keeping warm during winter.

    Characteristics of Synthetic Fibres

    1. Strength: Synthetic fibres are generally stronger than natural fibres, providing durability and resilience to the products made from them.

    2. Crease-Resistant and Wrinkle-Resistant: Synthetic fibres have a natural resistance to creasing and wrinkling, helping garments and fabrics maintain a smooth appearance even after extended use or storage.

    3. Moth-Resistant: Unlike some natural fibres, synthetic fibres are not attractive to moths and insects, making them less prone to damage from pests.

    4. Elasticity: Synthetic fibres possess elasticity, allowing them to stretch without breaking. This property is beneficial for items like sportswear and hosiery, providing comfort and flexibility.

    5. Water and Sweat Repellent: Synthetic fibres do not absorb water or sweat easily, which can be advantageous for certain applications like rainwear or athletic clothing. However, this can make them less comfortable to wear in hot and humid weather.

    6. Easy Maintenance: Synthetic fibres are relatively easy to maintain and clean, often requiring simple washing and care instructions.

    7. Highly Inflammable: One drawback of synthetic fibres is their high flammability. They can ignite and burn quickly, which can be hazardous if proper precautions are not taken.

    8. Non-Biodegradable: Unlike natural fibres, synthetic fibres are non-biodegradable, meaning they do not easily decompose in the environment. This can lead to pollution and environmental concerns.

    9. Melting Point: Synthetic fibres have a relatively low melting point, which means they can melt when exposed to high temperatures. As a precaution, they should not be worn near open flames or in the kitchen where heat sources are present.

    Synthetic fibres offer a range of advantageous properties, but they also come with some limitations and environmental implications that need to be considered when choosing their applications and usage.

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    Plastics are an essential part of our daily lives, found in a wide range of products and applications. They are a type of polymer, which is a large molecule made up of repeating units called monomers. Plastics are derived from petrochemicals, which are substances obtained from petroleum, a fossil fuel.
    Plastics have become integral to modern life due to their versatility, lightweight nature, and cost-effectiveness. They find application in countless sectors, ranging from the construction and automotive industries to healthcare and electronics.

    There are two primary types of plastics: thermoplastic and thermosetting.

    I. Thermoplastic

    a) Thermoplastic plastics have a unique property - they become soft and malleable when heated and can be easily moulded into different shapes.
    b) This characteristic allows them to be melted and moulded repeatedly without undergoing any significant chemical changes.
    c) Common examples of thermoplastic plastics include polyether, PVC (Polyvinyl Chloride), and polystyrene.
    d) The ability to reshape thermoplastics through heating makes them highly versatile in manufacturing processes. They are widely used in various applications, such as packaging materials, plastic bottles, toys, and household items.

    II. Thermosetting

    a) In contrast, thermosetting plastics once moulded into a specific shape, cannot be softened or reshaped upon heating.
    b) Once they undergo the initial curing process, they become hard and rigid.
    c) Examples of thermosetting plastics include Bakelite and melamine.
    d) Thermosetting plastics exhibit excellent durability and heat resistance, making them suitable for electrical components, kitchenware, and various industrial applications.

    Characteristics of Plastics

    Plastics, as versatile polymers, exhibit a range of unique characteristics that have made them indispensable in various industries and everyday items. Some key characteristics of plastics are:

    1. Poor Conductors of Heat and Electricity

    a) Plastics possess low thermal and electrical conductivity, which means they do not easily transfer heat or electricity.
    b) This property makes plastics suitable for use in electrical insulation and as components in electrical appliances, where safety and insulation are essential.

    2. Light, Strong, and Durable

    a) One of the outstanding features of plastics is their exceptional strength-to-weight ratio. They are relatively lightweight yet possess remarkable strength and durability.
    b) This combination of properties makes plastics an ideal choice for manufacturing lightweight products that still maintain structural integrity, such as car components and aircraft parts.

    3. Non-Reactive to Air and Water

    a) Plastics are non-reactive materials, meaning they are not affected by exposure to air or water.
    b) Unlike some metals that corrode or rust upon contact with moisture and oxygen, plastics remain stable and do not undergo chemical changes when exposed to these elements.
    c) This characteristic ensures that plastic products have a longer lifespan and resist degradation from environmental factors.

    4. Non-Biodegradable

    One significant drawback of plastics is their non-biodegradable nature. Plastics are not easily decomposed by natural processes, leading to long-lasting environmental pollution.

    5. Resistance to Rust

    a) Unlike metals, plastics do not rust. This property is particularly advantageous for outdoor applications, where exposure to moisture and corrosive elements could damage metal components.
    b) Plastics' resistance to rusting makes them a preferred choice for various outdoor products like garden furniture, playground equipment, and water-resistant coatings.

    The adaptability and diverse characteristics of plastics have revolutionized multiple industries, from packaging and construction to healthcare and electronics. However, their non-biodegradable nature demands a responsible approach towards plastic use and waste management to ensure a sustainable and environmentally conscious future.

    Environmental Impact of Plastic

    1. Pollution from Burning Plastics

    a) When plastics are burned, like in some waste disposal methods, they release harmful fumes into the air.
    b) These fumes contain toxic chemicals that can harm our health and contribute to air pollution.

    2. Non-Biodegradability

    a) One of the most concerning aspects of plastics is their non-biodegradable nature. Plastics do not undergo natural decomposition processes like organic materials.
    b) Instead, they persist in the environment for extended periods, taking several years to decompose. As a result, plastic waste accumulates in landfills, oceans, and other natural habitats, posing a threat to wildlife and marine life.

    3. Threat to Wildlife

    a) Plastic waste can end up in our oceans and other habitats. Marine animals, birds, and even land animals may mistake plastic for food and accidentally eat it. This can lead to serious health problems and even death for these animals.

    4. Disrupting Ecosystems

    a) Plastic pollution can also disrupt ecosystems. When plastic waste accumulates in water bodies, it can alter the balance of marine life and harm fragile aquatic environments.

    Addressing the Plastic Problem

    Some steps that can be followed to mitigate the environmental effects of plastics are:

    1. Reduce Plastic Consumption: Minimizing the use of single-use plastics, such as plastic bags and disposable cutlery, can significantly reduce plastic waste generation.

    2. Recycling: Encouraging recycling of plastics can divert them from landfills and help in producing new products, reducing the need for more plastic production.

    3. Biodegradable Alternatives: Promoting the use of biodegradable plastics made from renewable resources can offer environmentally friendly alternatives.

    4. Waste Management: Implementing efficient waste management systems is crucial to ensure proper disposal and recycling of plastic waste.

    5. Public Awareness: Educating the public about the environmental impact of plastic and fostering a sense of responsibility towards plastic use and waste management is essential.

    By adopting sustainable practices and embracing innovative solutions, we can work towards minimizing the negative impact of plastics on our planet and preserving the environment for future generations.

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