Polyester is a synthetic fibre which remains wrinkle free and is easy to wash. It is light, durable and takes less time to dry. So, it is quite suitable for making dresses and other clothes.
Synthetic fibres are man-made fibres. They are made by the chemical processing of petrochemicals.
Rayon is manufactured from purified cellulose, primarily from wood pulp, which is chemically converted into a soluble compound. It is then dissolved and forced through a spinneret to produce filaments which are chemically solidified, resulting in synthetic fibres of nearly pure cellulose. Therefore, rayon is manufactured from naturally occurring polymers and is therefore considered a semi-synthetic fibre.
Coal, water and air are used in the manufacture of nylon.
Terylene and Terrycot
Rayon is a cheap substitute of silk.
Three things made of polyester are:
Socks, ropes, tents and toothbrushes are made of nylon.
Rayon is mixed with cotton to make bed sheets and mixed with wool to make carpets.
Nylon is strong, elastic and light. It is also lustrous and easy to wash. So, it has become popular for making clothes.
Acrylic is a synthetic fibre which resembles wool. It is durable and inexpensive and can be easily dyed. It is used to make sweaters, blankets, shawls and other thermal wear.
Acrylic is lightweight, soft and warm with wool-like feel. It is readily available in a variety of colours. The wool obtained from natural sources is quite expensive whereas acrylic fibre is relatively cheaper. It is also strong and more durable than wool. Due to these properties, acrylic is considered as a substitute of wool.
Nylon rope is more durable, elastic, strong and does not break easily as compared to ropes made of cotton or jute. This is the reason why nylon ropes are used in rock climbing.
Nylon is a synthetic fibre. It catches fire easily and melts on heating. The melted fabric sticks to the body of a person wearing it, which is dangerous. This is why Tina’s mother has warned her against wearing nylon clothes while working in the kitchen.
The following properties make the synthetic fibres more popular than natural ones for making clothes:
Nylon has the advantages of being strong, elastic and light. A nylon thread is stronger than a steel wire of the same thickness and can support more weight. It is used to make parachutes and ropes for rock-climbing.
Disadvantages of synthetic fibres are:
Sam should buy cotton shirts for summer. Synthetic shirts will be uncomfortable as they do not have sufficient pores for the sweat to come out, evaporate and cool the body whereas the large pores of cotton shirts allow the body sweat to come out through them, evaporate and make the person wearing it feel cool and comfortable.
Silk has a beautiful texture. Because it is expensive to produce, people began to look for ways to produce silk artificially. Towards the end of the nineteenth century, scientists succeeded in creating a fibre by chemical treatment of wood pulp. The fibre had similar properties as silk. The scientists called the fibre rayon or artificial silk. Rayon is cheaper than silk but can be woven like silk fibres. It can be mixed with cotton to make bed sheets and with wool to make carpets.
Synthetic fibres are made of petrochemicals. Their manufacture does not depend upon plants and trees. Forests are not destroyed to manufacture synthetic clothes and other items. So, indirectly manufacturing synthetic fibres actually helps in the conservation of forests.
Nylon fibres are stronger than steel fibres of the same thickness. But steel is much harder than nylon. Steel cannot be cut easily and does not melt easily. Bridges need to be made of materials which are hard and strong and can withstand weight. Although nylon is strong and can withstand weight, it is not hard. Being a synthetic fibre, nylon melts when heated and can be cut easily, too. Therefore, nylon cannot be used to build bridges.
Thermosetting plastic and thermoplastic
Bakelite and Melamine.
Plastic is very light, strong, durable and can be moulded into different shapes and sizes. That is why plastic objects are available in all possible shapes and sizes.
Since plastic is non-reactive, it does not get corroded easily by diluted acids and alkalis. Therefore, some plastic bottles are commonly used to store mild chemicals.
Metals like iron rust when exposed to moisture and air. But plastic does not react with either water or air and does not corrode easily. That is why a bucket made of plastic does not corrode like a bucket made of iron.
Melamine is a versatile material. It resists fire and can tolerate heat better than other plastics. Therefore, it is used to make kitchenware.
Plastic takes several years to decompose, so it is not environment-friendly. It burns slowly and does not easily get completely burnt. During burning, it releases poisonous gases, causing air pollution. Therefore, you should use jute bags instead of plastic bags.
Plastic is non-biodegradable. When thrown on the road, it can enter the drainage system, causing clogging of drains. Therefore, we should not throw plastic bottles on the road.
Since thermoplastics can be softened easily on heating again and again and can be moulded into any desired shape, they are recyclable. On the other hand, thermosetting plastics cannot be re-softened on heating and moulded. Due to this reason, thermosetting plastics are non-recyclable.
Thermoplastics: Plastics which get deformed easily on heating and can be re-moulded repeatedly without undergoing any chemical changes are called thermoplastics. Polythene and PVC are examples of thermoplastics.
Thermosetting plastics: Plastics which can be moulded only once and after solidification cannot be softened on heating are called thermosetting plastics. Bakelite and melamine are examples of thermosetting plastics.
Handle and bristles of a toothbrush should not be made of the same material because the handle of a toothbrush has to be hard and rigid whereas the bristles of a toothbrush have to be soft and flexible. This means that the handle of a toothbrush should be made of a thermosetting plastic which is a hard material and its bristles should be made of a thermoplastic which is a soft material.
A substance which gets decomposed naturally by bacterial action is called biodegradable. For example, dead animals and human excreta are decomposed into simpler compounds by bacteria.
A substance which does not decompose naturally into simpler compounds by bacterial action is called non-biodegradable. For example, plastic bags and aluminium cans are non-biodegradable.
a) Plastics should be recycled, and it is safe to store food in recycled plastic containers.
b) Due to their non-reactive nature, some plastic containers are used in the chemistry laboratory to store concentrated acids.
c) You should not throw plastic wrappers or plastic bottles on beaches as doing so harms the ecosystem.
a. False. Plastics should be recycled. However, during recycling, some colouring agents are added, which are harmful if consumed. So recycled plastic containers should not be used to store food.
b. False. Plastic containers are non-reactive, and mild chemicals can be stored in them. However, concentrated acids are highly corrosive and can melt plastic. So, they are stored in glass containers.
c. True. Plastic wrappers are non-biodegradable and can cut off air from animals living underground or aquatic animals and plants. If they cannot breathe because the surface is clogged with plastic wrappers, they eventually perish. They can also choke animals who swallow them.
Three important properties of plastic are:
i. Plastic is non-reactive. Plastic does not react with water and air. It does not get corroded easily. Therefore, plastic containers are used to store various kinds of materials.
ii. Plastic is light, strong and durable. Plastic can be moulded into various shapes and sizes. It is generally cheaper than metal; therefore, it is widely used in industries and for making household articles.
iii. Plastic is a poor conductor of heat and electricity. Electric wires have plastic coverings, and handles of screwdrivers and cookware are also made of plastic.
Due to their light weight, low price, strength, durability and ease of handling, plastic containers are used to store food items, water, milk, pickles, dry food, medicines and mild chemicals. Metals like iron get rusted when exposed to moisture and air. But plastic does not react with water and air and so does not get corroded easily. Therefore, plastic containers are used to store various kinds of materials, including many mild chemicals. After their use or breakage, they can be sold as scrap and be recycled.
Since plastic is non-biodegradable, it is not environment-friendly. Plastics on burning release poisonous gases causing air pollution. When thrown in water bodies, it causes water clogging and harms aquatic life. If animals consume plastic, it chokes their respiratory system causing death. Therefore, it is advised to be careful with plastic use.
a) Saucepan handles: Saucepan handles are made of bakelite, a thermosetting plastic. Since bakelite is hard and a bad conductor of heat, the handles retain their shape and can be held by us, even if the saucepan is very hot.
b) Electrical plugs and switches: These are also made of bakelite, which is a poor conductor of electricity and can tolerate heat better than other plastics. Hence, it prevents possible fire in electrical installations due to over-heating. It also protects you from electric shocks. In addition, it does not get deformed or get softened due to over-heating.
Ways to limit the consumption of plastics are as follows:
Advantages of using plastic containers to store food:
a) Do not react with food, air or water
b) Are strong and light
c) Come in various sizes, shapes and colours