Class 8 Science Chapter 3: Synthetic Fibres and Plastics Notes Important for all Competitive Examinations

Introduction

You must have heard of fibres and fabrics.

Our clothes are made of fabrics and fabrics are made from fibres.

Fibres are obtained both naturally and artificially. Many household articles are also made from fibres.

For example, carpets, ropes, bags, curtains etc are made from fibres.

Fibres are of two types - natural and artificial. Man-made or synthetic fibers are also known as artificial fibers.

Wool, silk, cotton etc are some examples of natural fibres.

What are Synthetic Fibres?

• A synthetic fibre is made by joining small units (chemical substancs) together.
• Many small units ( monomers) combine together to form a large single unit that is called a polymer.
• 'Poly' means many and 'mer' means unit i. e. polymer is made of many repeating units.
• Cotton is natural fibre and it is made of polymer called cellulose made up of a large number of glucose units.

Types of Synthetic Fibres

Rayon

• Silk was discovered in China and was initially a closely guarded secret.
• Fabric made from silk was very expensive due to its beautiful texture.
• Scientists attempted to create artificial silk, and were successful in the late 19th century with the creation of rayon.
• Rayon is a man-made fiber created through the chemical treatment of wood pulp.
• Rayon is cheaper than silk and can be woven and dyed like silk.
• Rayon is often mixed with other materials, such as cotton or wool, for use in products such as bed sheets and carpets.

Nylon

• Nylon is a man-made fiber that was created in 1931 using coal, water, and air.
• Nylon is the first fully synthetic fiber.
• Nylon is strong, elastic, light, lustrous, and easy to wash, making it popular for use in clothing.
• Nylon is used in a variety of products, including socks, ropes, tents, toothbrushes, car seat belts, sleeping bags, curtains, parachutes, and ropes for rock climbing.
• A nylon thread is stronger than a steel wire.

Polyester and Acrylic

• Polyester is a synthetic fiber that is used to make fabric that does not wrinkle easily and is easy to wash.
• Terylene is a type of polyester that can be drawn into fine fibers for weaving.
• Polyester is commonly used to make clothing, including shirts and dresses.
• Polyester fabric is wrinkle resistant and easy to clean, making it a suitable choice for dress material.
• PET (polyethylene terephthalate) is a form of polyester that is used to make a variety of products, including bottles, utensils, films, and wires.
• Polyester, including PET, can be found in a range of everyday items, such as bottles, utensils, films, and wires.
• Polyester is made up of repeating units of an ester chemical. Esters are responsible for the smell of certain fruits.
• Polycot, polywool, and terrycot fabrics are made by mixing polyester with other fibers, such as cotton or wool.
• Polycot is a mixture of polyester and cotton, while polywool is a mixture of polyester and wool.
• Many winter clothing items, such as sweaters and blankets, are made from synthetic fibers like acrylic rather than natural wool.
• Acrylic fibers are cheaper and more durable than natural wool fibers.
• Synthetic fibers, including acrylic, melt when heated, which can be dangerous if clothing catches fire.
• Synthetic fibers are made from petrochemicals and produced through various processes.

Characteristics of Synthetic Fibres

• On a rainy day, it would be best to use an umbrella made from a synthetic fiber because they are more water resistant and dry faster than natural fibers.
• Synthetic fibers are popular for clothing because they are durable, affordable, readily available, and easy to maintain.
• Synthetic fabrics generally soak up less water and dry faster than natural fabrics.
• Synthetic fabrics are generally more durable, cheaper, and easier to maintain than natural fabrics.

Plastics

• Plastic is a type of polymer that can be molded into a variety of shapes and sizes.
• Plastic can be recycled, reused, colored, melted, rolled into sheets, or made into wires.
• Plastic is easily moldable, which makes it useful for a wide range of applications.
• Some plastic articles can be easily bent while others break when forced to bend.
• Plastic that becomes deformed when heated and can be easily bent is called a thermoplastic, examples include polythene and PVC.
• Plastic that cannot be softened by heating after being molded is called a thermosetting plastic.
• Bakelite is a type of thermosetting plastic that is a poor conductor of heat and electricity and is used for making electrical switches and handles.
• Melamine is a versatile thermosetting plastic that resists fire and can tolerate heat well, and is used for making floor tiles, kitchenware, and fire-resistant fabrics.
• Polythene is a type of plastic that is used to make commonly used polythene bags.

 Plastics as Materials of Choice

• Plastic containers are popular for storing food items because they are lightweight, affordable, strong, and easy to handle.
• Plastic containers are lighter than metal containers and are used in a variety of industries, including transportation and aerospace.
• Plastic is used to make a wide range of products, including slippers, furniture, and decorative items.
• Plastic is an important material in many industries and is used for a wide range of purposes, including packaging, cooking, and medical instruments.
• Special types of plastic, such as Teflon, have non-stick properties and are used in cookware.
• Some plastics are fire-resistant, such as melamine, which is used in fireman uniforms.
• Plastics have many useful properties, including being lightweight, strong, and durable, and being non-reactive and poor conductors of heat and electricity.
• However, it is important to recycle and properly dispose of plastic to reduce environmental impact.

The Characteristics Properties of Plastics

• Plastic does not corrode easily and does not react with water or air, making it useful for storing various materials including chemicals.
• Plastic is lightweight, strong, durable, and can be molded into various shapes and sizes.
• Plastic is generally cheaper than metal and is widely used in industry and for household products.
• Plastic containers are used in daily life for various purposes due to their lightweight, strength, and durability.
• Plastic is a poor conductor of heat and electricity, making it useful for covering electrical wires and as a handle material for tools and cooking utensils.

Plastics and the Environment

• Plastic waste accumulates in our homes due to its widespread use in packaging, such as plastic wrap and polythene bags.
• Disposal of plastic waste can be a major problem because it is a non-biodegradable material.
• Biodegradable materials can be decomposed through natural processes, such as action by bacteria.
• Non-biodegradable materials, including plastic, do not easily decompose through natural processes. This makes their disposal more challenging.
• Plastic takes a long time to decompose, making it harmful to the environment.
• Plastic pollution is a major environmental concern.
• The burning process of plastic is slow and often incomplete, releasing poisonous fumes into the air and contributing to air pollution.
• To address the problem of plastic pollution, there are several potential solutions, including reducing plastic consumption, properly disposing of plastic waste, and recycling plastic.
• To reduce plastic consumption, it can be helpful to bring your own reusable bags when shopping, and to choose products that are not packaged in plastic when possible.
• Properly disposing of waste can also help to reduce plastic pollution. This includes separating biodegradable and non-biodegradable waste, and properly disposing of plastic waste in designated recycling facilities.
• Recycling plastic can help to reduce the demand for new plastic, and can also conserve resources and energy. However, it is important to note that not all plastic can be recycled, and that the quality of recycled plastic may not be as good as that of new plastic.
• The 5 R principle (Reduce, Reuse, Recycle, Recover, Refuse) is a helpful guideline for making more environmentally-friendly choices in our daily lives. By reducing our consumption of plastic and other resources, reusing items whenever possible, and recycling when appropriate, we can all contribute to a more sustainable future.
• Animals, including birds and small mammals, can be attracted to garbage dumps and may eat food waste, including plastic materials like polythene bags and wrappers.
• The ingestion of plastic can have serious consequences for these animals, including choking and blockages in the respiratory system or digestive system. In severe cases, it can be fatal.
• Carelessly discarded plastic materials, such as polybags, can also contribute to environmental problems, such as clogged drains and litter in public places.
• To help keep public places clean and free of plastic, individuals can take a number of actions, including properly disposing of their own waste, using reusable bags and containers, and participating in community clean-up efforts. It is also important to be mindful of our actions and to think twice before littering or improperly disposing of waste.
• Throwing plastic bags in water bodies or on the road can have negative impacts on the environment and wildlife.
• Using cotton or jute bags instead of plastic bags can help to reduce plastic consumption and waste.
• Minimizing the use of plastic materials in our daily lives is an important step we can take to reduce plastic pollution. Some ways to do this include using reusable containers and bags, such as a steel lunch box instead of a disposable plastic one.