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DEFINITION
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"Plastics
are defined as the polymers (solid materials) which become mobile
on heating and thus can be cast into moulds." |
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| Plastics are synthetic polymers which can easily be deformed. They are formed by the addition or condensation polymerization. Plastics are not affected by the action of acids or bases. They have great tendency to deform. | ||||
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TYPES
OF PLASTICS
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There
are two main types of plastics: 
THERMOPLASTICS
THERMOSETTING PLASTICS |
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THERMOPLASTICS
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| Plastics that become soft on heating and melt on heating and can be moulded again and again are known as thermoplastics. Repetitive heating of thermoplastics does not cause permanent change in properties or composition. They are addition polymers. | ||||
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EXAMPLES
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Polyethene.
Nylon.
PVC.
PVA. |
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THERMOSETTING
PLASTICS
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| These are the plastics that can be softened on heating but they become permanently hard on cooling. They can not be remoulded again. They are insoluble in any solvent whether organic or inorganic. They are condensation polymers. | ||||
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EXAMPLES
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Bakelite.
Urea aldehyde.
Silicones |
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RAW
MATERIALS OF PLASTICS
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| Plastics are made from the following materials: | ||||
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Plasticizers: They improve the softening, decrease brittleness and workability
of plastics. They are organic
substances.
Stabilizers: They prevent chemical degradation of plastics. By nature
they are antioxidants.
Fillers: They increase the tensile
strength of plastics. They are wood flour
and glass wool.
Reinforcing agents: They increase its mechanical strength. Example is glass
fibre.
Pigments
: They are used to impart a particular color to the plastic. |
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POLYETHYLENE
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| Polyethylene is commonly known as "POLYETHENE" is the most common plastic. It is a polymer of ethene. It is prepared by heating ethene at 200oC at high pressure i.e 1000 atmosphere. | ||||
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n[CH2=CH2]è
[-CH2-CH2-]n
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USES
OF POLYETHYLENE
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Plastic shopping bags. |
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PVC
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| PVC stands for "POLY VINYL CHLORIDE". It is a polymer of vinyl chloride (CH2=CHCl). It is prepared by heating vinyl chloride at 60oC in the presence of hydrogen peroxide. | ||||
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n[CH2=CHCl]è
[-CH2-CHCl-]n
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USES
OF PVC
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Electric cables.
Gramophone records.
Suit case. |
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PVA
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| PVA stands for "POLY VINYL ACETATE". It is a polymer of vinyl acetate (CH2=CHO.CO.CH3). It is prepared by heating vinyl chloride at 60oC. | ||||
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USES
OF PVA
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Chewing gum.
Water proofing.
Textile industry. |
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BAKELITE
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| Bakelite is a condensation polymer of phenol and formaldehyde. Bakelite is widely used for making moulded products. | ||||
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USES
OF BAKELITE
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| Electric
switches, electric boards.
Camera's body.
Radio.
Telephone.
Buttons |
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| For latest information , free computer courses and high impact notes visit : www.citycollegiate.com | ||||