Presentation describe about the manufacturing process of natural rubber.

1. I. NATURAL RUBBER
Chapter 2: Carbon Compounds

2. Natural Polymer
 Natural polymer:
Polymer that exists naturally and is not made by man
from chemical reaction
 Examples
Natural polymer Monomer
Natural rubber Isoprene
Starch Glucose
Cellulose Glucose
Protein Amino acid

3. Natural rubber
 Obtained from the latex (rubber tree)
 White milk-like fluid
 Poly(isoprene)
 Monomer: 2-methylbutan-1,3-diene
C CH
CH3
CH3CH3
n C CH
CH3
CH2CH2
n

4. Properties of Natural rubber
Properties
of natural
rubber
Easily
oxidized
by air
Elasticity
decreases
Soft
Sensitive
to heat

5. Use of natural rubber
 Rubber tubes
 Shoe soles & door stoppers
 Rubber bands
 Rubber hoses, rubber caps

6. Coagulation process
Latex is milk-like liquid obtained from tapped rubber
tree
 Latex is a colloid (group) which contains suspension
of rubber particles in water.
 Each group of particles of rubber is surrounded by a
layer of protein membrane.
 This membrane is negatively charged and will
repel with each other.
 So, natural rubber remain in liquid form.

7. The coagulation process
Has 2 ways the rubber can be coagulated
 Added with acid (fast reaction)
 Action of bacteria (slow reaction)

8. 1 2
3
4
Long-chain
rubber molecules

9. (a) Added with acid
 Acid (methanoic acid or ethanoic acid) which
consists of H+ ion is added into the latex.
 The H+ ion from acids neutralize the negatively
charged protein membrane.
 The rubber particles collide with each other.
 Protein membrane of the rubber
particle breaks.
 Rubber molecules clump together. Latex
coagulates.

10. (b) Action with bacteria
 Bacteria from the air enter the latex.
 The growth of bacteria produces lactic acid.
 Lactic acid causes coagulation of latex.

11. Prevention of coagulation
 By adding ammonia, NH3 solution.
 Ammonia solution consists of OH- ion that
neutralize the acid produced by the bacteria.
 The rubber particles remain negatively charged.
 Coagulation of latex is prevented.

12. Vulcanization of rubber
 Natural rubber can be vulcanized by the following
manner;
(a) Heating natural rubber with sulphur and a little bit
of zinc oxide (catalyst)
or
(a) Immersing strips of natural rubber in sulphur
monochloride, SCl or disulphide dichloride, S2Cl2
in methylbenzene

13. C=C
C=C
C=C
C=C
C C
C
C
C
C
S
S
S
S
S
S
vulcanization

14. Vulcanization making rubber:
 Tough materials
 More elastic
a. The sulphur atoms form cross linkages between
the long rubber molecules
b. This reduces the ability of the rubber polymers to
slide over each other
c. The rubber molecules return to their original
positions after being stretched
 More heat resistance
 Less soluble in organic solvent

15. Vulcanized VS Unvulcanized rubber
Properties Natural rubber
Vulcanized
rubber
Elasticity
Hardness
Strength
Melting point
Resistance to
temperature
Resistance to
oxidation