• Fibres can be natural as well as synthetic depending on the source of the raw material.
• Fibres are made up of molecules called polymers.
POLYMERS
Polymers are huge molecules- usually consisting of long chains made from thousands of similar molecules called monomers.
· Polymers are huge molecules- usually consisting of long chains made from thousands of similar molecules called monomers.
· The structure of a monomers can be compared to that of a beaded necklace- with the beads being the monomers.
· The process by which monomers are linked together to form polymers is called polymerization.
· Polymers can be linear or cross-linked in structure.
There are two types of fibres. They are
1. Natural Fibres: - Natural fibres may be made from Plants or Animals.
Cotton. Jute and Coconut are Plant fibres where as Silk and Wool are Animal fibre.
2. Synthetic Fibres: - Synthetic fibres are man-made fibres. They are made from bye- products of petroleum known as the petrochemicals.
Examples:-Rayon, Nylon, Polyester, Acrylic
Polymers:- Poly = Many Meres= Units
Polymers are long chain molecules
formed by the combination of many smaller units known as monomers
(mono=single, mere=units
The process of formation of long chain
compounds polymers by the combination of monomers is called polymerisation reaction.
Rayon is a man made fibre obtained
from wood pulp(cellulose) on chemical treatment with NaOH,Carbon disulphide and
Sulphuric acid .
he properties of rayon is similar to silk and it
shrink like silk.So it is commonly called Artificial Silk
Properties of rayon :-
· Rayon is soft, durable and strong fibre.
· It can be dyed into various colours.
Uses of rayon :-
· Used for making fabrics
· For making bed sheets and carpets
· Used to make surgical products like bandages.
Nylon:-
· Nylon is the first fully synthetic fibre made in 1931.
· Its name is derived from the cities of New York and London, where it was first marketed.
· It was prepared from coal, water and air.
· Nylon is made by the polymerisation of a dicarboxylic acid with a diamine.
Properties of nylon :-
· Very strong (stronger than steel wire)
· Elastic and Light
· Wrinkle and Wear resistant
· Easy to wash
· Absorbs very little water
· Lustrous in appearaance
Uses of nylon :-
· Used for making fishing nets.
· Various fabrics are made from nylon.
· Ropes are made from nylon
· Tooth brush, tents, car seats etc are made.
· Parachutes are made using nylon.
· Curtains, bags, socks, etc are made.
Polyester:-
· Polyesters are polymers of alcohols and carboxylic acids.
· Terylene is popular polyester formed from terepthallic acid and glycol.
· PET - Poly Ethylene Terepthallate is familiar form of polyester used for making bottles, films, wires, vessels, etc.
· With cotton it makes Polycot and with wool it makes Poly-wool.
Properties of polyester-
· Very strong
· Elastic
· Light
· Crease-resistant
· Water-resistant
Uses of polyester-
· It is used to make clothes such as trousers, shirts
· Being water resistant it is used to make jackets and garments used in wet or damp environments
· PET is a form of polyester used to make bottes, films, utensils, wires, etc
Acrylic :-
· It is a type of synthetic fibre that resembles wool in it’s properties.
· Clothes made from acrylic are cheaper than wool.
Properties of acrylic
Acrylic Uses:
· Acrylic Fabrics-
· Paints
· Utensils
Characteristics of Synthetic Fibres :-
· Synthetic fibres are less expensive or affordable to all.
· They are durable.
· Readily available.
· Easy to maintain.
· Synthetic clothes dry quickly.
· Light weight
· Chemically inert.
Advantagesof synthetic fibres-
· Crease-resistant
· Elastic
· Moth proof
· Easy to wash
· Last for along time
Disadvantages of synthetic fibres
· Do not absorb sweat
· Stick to the body in hot and humid weather
· Catches fire very rapidly
· Melt on heating and stick to the body and can cause severe burn injuries
Plastics
A material is said to be plastic if it can be moulded or formed into different shapes. They are made of polymers.
Sources of plastics
The main source of these plastics is crude oil.
Properties
of plastics with their linked uses
· INSOLUBLE IN WATER -They are waterproof and insoluble in water and so are used to make raincoats, water bottles, buckets etc.
· LOW THERMAL CONDUCTIVITY-They are poor conductors of heat and that is why they are used to make handles of cooking utensils and as insulating wool in refrigerators.
· POOR CONDUCTOR OF ELECTRICITY-They are poor conductors of electricity and so electric wires, cords of electrical appliances and cables have a plastic coating.
· NON-REACTIVE-They have no reaction with water and air. They do not corrode easily. They are therefore used to store chemicals such as acids.
· INFLAMMABLE
They are inflammable i.e. burns easily and
so can be melted, moulded and recycled into different products.
Types of
plastics
Plastics can be
categorized into two different groups depending on their reaction to heat. These are:
1. Thermoplastics
2. Thermosetting plastics
Difference between Thermoplastics and thermosetting plastics
|
THERMOPLASTICS |
THERMOSETTING PLASTICS |
|
In these plastics, the
process of softening by heating and hardening on cooling can be repeated
again and again to soften
the plastic to get different shapes. |
These plastics can be
softened by heating only once. Once they are put into a mould and allowed to harden on cooling, they cannot be
softened again on heating. |
|
They cannot maintain
their shape and size at very high temperature. Ex. – Polythene |
They can maintain their
shape and size even at very high temperature. Ex. – Bakelite |
Some common plastics and their uses
|
MAN-MADE PLASTIC |
TYPE OF PLASTIC |
PROPERTY |
USES |
|
Polythene |
Thermoplastic |
Strong but flexible, can be rolled
into sheets or moulded into any shape, water resistant |
Sheets of polythene are
used to pack liquids such as milk, polythene pipes are used to transport
liquids such as oil or water, polythene containers are used to store liquids |
|
Polyvinyl chloride (PVC) |
Thermoplastic |
Tougher than polythene, insulator |
Used as covering for electric wires,
used to make shoes, handbags, furniture, upholstery, floor coverings,
raincoats and bottles |
|
Polystyrene |
Thermoplastic |
Easily moulded |
Used as a packaging material for
delicate objects like electronic items and to make thermocol, used to
insulate the hollow walls of refrigerators |
|
Perspex |
Thermoplastic |
Transparent like glass, but much
stronger |
Used as a substitute for glass, for
making windows in aeroplanes and windscreens of cars |
|
Teflon or PTFE (polytetra -fluoroethylene) |
Thermoplastic |
Slippery, not affected by heat and
does not react chemically with
other substances |
Used as a non-stick coating on pans
and other cooking utensils |
|
Bakelite |
Thermosetting |
Harder than other plastics and a
good electrical insulator |
Used for making buttons, plugs,
switches and other electrical fittings |
|
Formica and Melamine |
Thermosetting |
Hard and smooth surface |
Used as table-tops, and for making crockery |
Problems with plastics
Though plastics are very useful, there is a concern today about their increasing use because of the following reasons:
· They are non-biodegradable, i.e. they cannot be decomposed by the microorganisms in the soil.
· Careless disposal of them chokes drains, chokes the soil and hinders the absorption of water by the soil.
· If eaten by animals, they may be killed.
· Plastic bags can also contaminate foodstuffs because of poisonous dyes getting absorbed into food.
· If burnt, they release poisonous fumes and pollute the air.
Saving environment by reducing plastic pollution
To reduce the problem of plastic pollution we need to do the following –
· Always remember and follow the 4R principle – Reduce, Reuse, Recycle, Recover
· Buy products with less plastic packaging.
· Practice and promote proper disposal
of plastics in your home.
· Use your own cloth or paper bags for shopping.
· Support recycling schemes and promote
support for one in your local area.
