1. Polymer is a large molecule formed by chains of monomer

2. There are 2 types of polymers

• natural polymers
• synthetic polymers

3. Natural polymers: polymers that exist naturally

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

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

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

8. 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

9. 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

10. The action of alkali on latex

• Alkali 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

11. 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

12. 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

13. Uses of vulcanised rubber

• Tyres of vehicles
• Rubber gloves
• Shoe soles