Polymer

9.3 Polymer
 
Polymer

Polymer is a large molecule formed by chains of monomer

 
Type of polymer
 

 
Natural polymers

Polymers that exist naturally

Natural polymer Monomer Uses
Starch Glukose Produces energy

Protein

Amino acid Build cells and body tissues
Natural rubber Isoprene To make rubber-based products
 
Synthethic

Man-made polymers using chemical susbtances

Synthethic polymer Monomer Use
Polythene

Ethene

To make plastic bottles, plastic bags and pails
Polystyrene

Styrene

To make packing container for electrical equipment
Perspex Methyl methacrylate To make aeroplane mirrors, windows for vehicles
Synthethic rubber Neoprene To make gloves, tyres and shoe soles

 

 
Polymerisation

Polymerisation: the process of joining the monomers through the formation of chemical bonds to produce a long-chain polymer

Depolymerisation: the process of splitting a long chain polymer into its monomer through chemical reactions

Addition polymerisation: polymerisation that involves a monomer of the same type by breaking a double bond into a single bond

 
Natural rubber
  • In latex, rubber molecules in the form of chains are covered with a layer of protein membrane
  • Negative charges surround the outer surface of the membrane
  • This causes the rubber molecules to repel each other
 
The action of acid on latex
  • An acid is added to the latex
  • Positively charges hydrogen ions from the acid will neutralise the negative charges on the surface of the protein membrane
  • Rubber molecules will collide with one another
  • This will break the protein membrane and the chaine of the rubber polymer
  • It coagulate to form solid lumps

* Bateria from air will also produces acid that neutralises the protein membranes of rubber molecules

 
The action of alkaline on latex
  • Alkaline is added to the latex
  • Negative charges hydroxide ions from the alkali will neutralise the hydrogen ions from the acid
  • Negative charges remian on the protein membrane
  • Rubber molecules will remain in liquid form
Vulcanisation of rubber 
  • Vulcanisation is a process of heating rubber with sulphur
  • It improves the properties of rubber and make it stronger
  • Rubber obtained throught the process is known as vulcanised rubber
 
Properties of vulcanised rubber
  • Hard
  • More elastic
  • Good electrical insulator
  • Difficult to be oxidised in air
  • Does not react with acid and alkali
  • Not permeable to liquid and air
  • Resistant to heat
 
Uses of vulcanised rubber
  • Tyres of vehicles
  • Rubber gloves
  • Shoe soles

Polymer

9.3 Polymer
 
Polymer

Polymer is a large molecule formed by chains of monomer

 
Type of polymer
 

 
Natural polymers

Polymers that exist naturally

Natural polymer Monomer Uses
Starch Glukose Produces energy

Protein

Amino acid Build cells and body tissues
Natural rubber Isoprene To make rubber-based products
 
Synthethic

Man-made polymers using chemical susbtances

Synthethic polymer Monomer Use
Polythene

Ethene

To make plastic bottles, plastic bags and pails
Polystyrene

Styrene

To make packing container for electrical equipment
Perspex Methyl methacrylate To make aeroplane mirrors, windows for vehicles
Synthethic rubber Neoprene To make gloves, tyres and shoe soles

 

 
Polymerisation

Polymerisation: the process of joining the monomers through the formation of chemical bonds to produce a long-chain polymer

Depolymerisation: the process of splitting a long chain polymer into its monomer through chemical reactions

Addition polymerisation: polymerisation that involves a monomer of the same type by breaking a double bond into a single bond

 
Natural rubber
  • In latex, rubber molecules in the form of chains are covered with a layer of protein membrane
  • Negative charges surround the outer surface of the membrane
  • This causes the rubber molecules to repel each other
 
The action of acid on latex
  • An acid is added to the latex
  • Positively charges hydrogen ions from the acid will neutralise the negative charges on the surface of the protein membrane
  • Rubber molecules will collide with one another
  • This will break the protein membrane and the chaine of the rubber polymer
  • It coagulate to form solid lumps

* Bateria from air will also produces acid that neutralises the protein membranes of rubber molecules

 
The action of alkaline on latex
  • Alkaline is added to the latex
  • Negative charges hydroxide ions from the alkali will neutralise the hydrogen ions from the acid
  • Negative charges remian on the protein membrane
  • Rubber molecules will remain in liquid form
Vulcanisation of rubber 
  • Vulcanisation is a process of heating rubber with sulphur
  • It improves the properties of rubber and make it stronger
  • Rubber obtained throught the process is known as vulcanised rubber
 
Properties of vulcanised rubber
  • Hard
  • More elastic
  • Good electrical insulator
  • Difficult to be oxidised in air
  • Does not react with acid and alkali
  • Not permeable to liquid and air
  • Resistant to heat
 
Uses of vulcanised rubber
  • Tyres of vehicles
  • Rubber gloves
  • Shoe soles