class 8th science solutions, Class 8th Solutions
20

Synthetic Fibres And Plastics

Synthetic Fibres and Plastics

The clothes which we wear are made of fabrics.Fabrics are made from fibres obtained from natural or artificial sources.We use it in clothing,medical,agriculture etc sector.

Fabrics are classified into 2 categories:

1.Natural Fibres 2.Synthetic Fibres

Natural Fibres

Those fibres which are obtained from natural sources are called natural Fibres.

Eg:Silk,Cotton,Wool etc

synthetic fibers

These are also known as man-made fibers. Synthetic fibers are obtained by chemical processing of petrochemicals. The synthetic fibers can be woven into a fabric, just like natural fiber. … Synthetic fibers and plastics are made up of molecules called polymers.

Types Of Synthetic Fibres

Rayons:

These are the most widely used semisynthetic fibres. They are derived from cellulose and are available in three different varieties— viscose, cuprammonium (or cupro) and acetate rayons.

Polysters:

The first synthetic fibre obtained was of this class. Polymers obtained by the reaction between certain sets of organic (carbon-containing) compounds form a melt which can be spun into filaments. The special property of these filaments is that they can be stretched several times their original length. Terylene and Dacron belong to this class of synthetic fibres. Terylene is used to make clothes. In general, polyesters are used to make textiles, bottles and insulating tapes.

Polyamides (nylons):

 

Nylon 6 and nylon 6, 6 are the most important fibres of this class. Nylon 6 is made of an organic compound which contains six carbon atoms. Nylon 6, 6 is made of a more complicated monomer. Nylon was first made in 1935.

It was intended to be a substitute for silk and was used in place of silk in parachutes in 1941, when the USA entered World War II. Nylon is very suitable for women’s wear. Having a high tensile strength, nylon is also used for making ropes.

Acrylics:

Acrylic fibres are a substitute for natural wool. These polymers decompose without melting. So, they are dissolved in a suitable solvent and the solution is forced through spinnerets to obtain filaments. The filaments can be cut into staples and the staples spun into yarns.

Acrylic fibres are crimpy (i.e., wavy) and not straight like polyester or nylon fibres. So acrylic yarns appear to be bulky and compete with wool. They are generally used to make knitwear, upholstery and artificial furs.

 

Acrylic fibres are not easily acted upon by moisture, chemicals or bacteria.

 

 

Plastic

The word ‘plastic’ comes from greek word “plastikos” that means “to form”. Plastic is made from petroleum and natural gas.

Plastics can be easily molded into any shape and sizes. Plastic is also defined as a material that can be heated and molded in any shape after cooling. For example: Polythene. Plastics can be recycled, reused, colored melted, rolled into sheets or made into wires. Some of the plastic has linear arrangement, while some has cross linked.

Properties of Plastic

  1. It is lightweight.
  2. It does not rust.
  3. It is easy to handle.
  4. It is reusable.
  5. It is non reactive.
  6. They are poor conductors of heat and electricity.

Example of Plastics

  1. Toys
  2. Plastic Chairs

Types of plastics

There are two types of plastics which are written below:

  1. Thermoplastics
  2. Thermosetting plastics

Thermoplastics

Thermoplastic is a plastic which gets deformed easily on heating and can be bent easily. On heating thermoplastics, there is no chemical change. For example: Polythene, polytetrafluroethylene (PTFE), polystyrene, and PVC (polyvinylchloride). These are used for manufacturing toys, combs, car grills and various types of containers.

Thermosetting plastics

There are some plastics which when molded once cannot be softened by heating again and again. These are called thermosetting plastics. For example: Bakelite and melamine. Bakelite is used for making electrical switches, handles of various utensils etc. Melamine is used for making floor tiles, kitchenware etc.

Uses

  1. It is used in making bottles.
  2. It is used in making plastic toys.
  3. It is used for packaging many goods like container etc

Plastic is not environment friendly. Therefore certain steps have to be taken it order to protect our environment. Like polythene, is a non-biodegradable substance which means that microorganisms cannot decompose them.

Steps that are required to protect the environment

  1. We should never throw plastic bags or other plastic articles into water bodies, drains or on roads.
  2. We should carry cotton or jute bags for shopping.
  3. We should buy products with less plastic packaging.
  4. We should encourage the people to recycle and reuse plastics.

As a citizen remember 4R’s principle:

Reduce: This means that anything that harms the environment should not be utilized or we should limit the use of that particular substance.

Reuse: This means that we should reuse the substances that does not harm our environment and it should be biodegradable.

Recycle: We should recycle the substances.

Recover: We should recover the substances that are useful for us.

Exercises

 

1.Some fibers are called synthetic because they are man-made and made by people by using some chemicals. In these fibers small units are there which by joining together forms a long chain. There are some fibres that are prepared by man by using chemicals. These are called synthetic fibres.

  1. b)it is obtained from wood pulp

3.a).Artificial or man made

b)petrochemicals

c)polymers

4.Nylon fibes are very strong as they are used for making ropes used for making parachutes and for climbing rocks.These uses of nylon are enough to explain their tensile strength.

5.. Plastic containers are preferred for storing food because of the following reasons: Plastic is non-reactive. It does not react with water and air. It is therefore, safe to keep food in plastic containers.

  1. Thermoplastics and thermosetting plastics are two separate classes of polymers, which are differentiated based on their behavior in the presence of heat. The material difference between the two is that thermoplastics can be remelted, while thermoset plastics remain in a permanent solid state once hardened.

7..Saucepan handles, Electric plugs/ switches/ plug   are made up of thermosetting plastics because they are poor conductors of heat. b.Electric plugs/switches/plug boards are made of thermosetting plastics because they are poor conductors of electricity reducing the risk of electrocution.

8.Recycled- Plastic toys, cooker handles, carry bags, ballpoint pens, plastic chairs.

Not recycled-Telephone instruments,cooker handles,electric switches.

9.Synthetic Fibres are made from extremely fine fibres so they do not have pores for the sweat to come out and cotton fibres have larger pores which allows sweat to come out easily and evaporayte quickly which makes us feel comfortable.So I will advise Rana to buy cotton shirts.

  1. Following examples show that plastics are non-corrosive in nature : (i) They are used to store chemicals. For example cleansing chemical are very reacticve and store in plastic bottle. (ii) They are used to store all types of food, as it does not react to materials stored in it.

  1. No. The handle and bristles of a tooth brush should be made of different materials. The handle of a toothbrush should be hard and strong, while the bristles should be soft and flexible.
  2. Avoid the use of plastics as far as possible. Plastics are non-biodegradable materials. So use of plastics is harmful for our environment.
  3. i-c

ii-d

iii-a

iv-b

  1. The natural fibres require raw materials from plants and animals. So they lead to cutting trees and killing of animals. Synthetic fibres are made up of chemicals and these chemicals are not available in forests. So manufacturing synthetic fibres is actually helping conservation of forests.
  2. Thermoplastics are poor conductors of electricity. To prove this creates a circuit.
    To create the circuit we require bulb, copper wires, a battery, a piece of metal, and a plastic pipe. Set up the circuit with the metal switch on the current, the bulb glows. Next set up the circuit with pipe switch on the current the bulb does not glow.
    From the experiment we conclude that plastic pipe (thermoplastic) cannot allow the current through pass it hence it is a poor conductor of electricity.

 

 

 

 

 

 

 

 

Related Posts