NATURALRUBBER…

NATURAL POLYMERS

1. PROTEIN AMINO ACID2. CARBOHYDRATE GLUCOSE3. NATURAL RUBBER ISOPRENE4. STARCH GLUCOSE5. CELLULOSE GLUCOSE

POLYMER MONOMER

NATURAL RUBBER

POLYMERIZATION OF RUBBER

PROPERTIES OF NATURAL RUBBER

COAGULATION OF LATEX

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

VULCANIZATION OF RUBBERDEFINITION:

Process for hardening rubber by treating it with sulphur compound.

PURPOSE : To improves the qualities/weakness of natural rubber (unvulcanized rubber)

COMPARING AND CONSTRAST THE PROPERTIES OF VULCANIZED & UNVULCANIZED RUBBER

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,So, VR high resistant to oxidation.

COMPARING AND CONTRASTING THE PROPERTIES OF VULCANIZED AND

VULCANIZED RUBBERSimilarities : Elasticity & Heat and electrical

insulatorDifferences

Vulcanized Rubber More elastic Harder Stronger Can withstand higher

Temperature Less easily oxidized Does not become soft

& sticky easily

Unvulcanized Rubber Less elastic Softer Weaker Cannot withstand

higher Temperature Easily oxidized Becomes soft &

sticky easily

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 buildon 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