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
|