Surapich Loykulnant Rubbers Lab, Polymer Research Unit National
Chapter 12 rubbers
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Transcript of Chapter 12 rubbers
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