This document discusses natural rubber, including its monomer (isoprene), polymerization, properties, and uses. It explains how natural rubber latex is prevented from coagulating through the addition of hydroxide ions. The key process of vulcanization is described, which cross-links rubber molecules with sulfur atoms to improve elasticity, strength, and heat and chemical resistance compared to unvulcanized rubber. Common uses of natural rubber are mentioned like tires, footwear, and vibration absorption applications due to its elastic properties.

1. NATURAL
RUBBER…

2. NATURAL POLYMERS
POLYMER MONOMER
1. PROTEIN AMINO ACID
2. CARBOHYDRATE GLUCOSE
3. NATURAL RUBBER ISOPRENE
4. STARCH GLUCOSE
5. CELLULOSE GLUCOSE

3. NATURAL RUBBER

4. POLYMERIZATION OF RUBBER

5. PROPERTIES OF NATURAL RUBBER

7. COAGULATION OF LATEX

8. TO PREVENT
COAGULATION OF
LATEX
 Hydroxide ions, OH- from alkali neutralise H+
produced by acid as a result of bacterial attack
on protein
 The protein membrane remains negatively
charged because there is no hydrogen ion, H+
 The rubber particles repel each other
 The rubber polymers cannot combine and
coagulate

9. VULCANIZATION OF
RUBBER
DEFINITION:
Process for hardening
rubber by treating it with
sulphur compound.
PURPOSE : To improves the
qualities/weakness of
natural rubber
(unvulcanized rubber)

10. COMPARING AND CONSTRAST THE PROPERTIES
OF VULCANIZED & UNVULCANIZED RUBBER

11. MECHANISM OF
VULCANIZATION OF LATEX
]]] The presence of cross-linkage of sulphur atoms
between the rubber molecules
]]] When vulcanized rubber is stretched and
release, the cross-linkage will ;
pull the chains back to their original
arrangement.
So, it improves the elasticity & strength of the
rubber
- increase the size of rubber molecules
-make vulcanized rubber more resistant to heat &
organic solvents
C=C Vulcanised rubber < C=C Unvulcanised rubber,

12. COMPARING AND CONTRASTING THE
PROPERTIES OF VULCANIZED AND
VULCANIZED RUBBER
Similarities : Elasticity & Heat and electrical insulator
Differences
Vulcanized Rubber Unvulcanized Rubber
 More elastic  Less elastic
 Harder  Softer
 Stronger  Weaker
 Can withstand higher  Cannot withstand higher
Temperature Temperature
 Less easily oxidized  Easily oxidized
 Does not become soft &  Becomes soft & sticky
sticky easily easily

13. USES OF NATURAL RUBBER
1) Elasticity of rubber - making tyres,
footwear,rubber threads, rubber foam,
conveyor belts,rubberized bitumen roads
2) Many buildings that are near to railways @
situated in earthquake prone areas are
build
on rubber blocks @ rubber bearings which
can help absorb vibration
3) Impermeability to gas @ liquid - Uses in
gloves, tubes & hoses
4) Vulcanized Rubber + Carbon tyres /air
craft tyres (to maintain their elasticity