Chapter 12 rubbers

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  • 1. NATURAL RUBBER…
  • 2. NATURAL POLYMERS POLYMER MONOMER1. PROTEIN AMINO ACID2. CARBOHYDRATE GLUCOSE3. NATURAL RUBBER ISOPRENE4. STARCH GLUCOSE5. CELLULOSE GLUCOSE
  • 3. NATURAL RUBBER
  • 4. POLYMERIZATION OF RUBBER
  • 5. PROPERTIES OF NATURAL RUBBER
  • 6. COAGULATION OF LATEX
  • 7. 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
  • 8. VULCANIZATION OF RUBBER DEFINITION:Process for hardeningrubber by treating it withsulphur compound.PURPOSE : To improves thequalities/weakness ofnatural rubber(unvulcanized rubber)
  • 9. COMPARING AND CONSTRAST THE PROPERTIES OF VULCANIZED & UNVULCANIZED RUBBER
  • 10. 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 originalarrangement. So, it improves the elasticity & strength of therubber- increase the size of rubber molecules-make vulcanized rubber more resistant to heat &organic solventsC=C Vulcanised rubber < C=C Unvulcanised rubber,
  • 11. COMPARING AND CONTRASTING THE PROPERTIES OF VULCANIZED AND VULCANIZED RUBBER Similarities : Elasticity & Heat and electrical insulator DifferencesVulcanized 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
  • 12. USES OF NATURAL RUBBER1) Elasticity of rubber - making tyres, footwear,rubber threads, rubber foam, conveyor belts,rubberized bitumen roads2) Many buildings that are near to railways @ situated in earthquake prone areas are build on rubber blocks @ rubber bearings which can help absorb vibration3) Impermeability to gas @ liquid - Uses in gloves, tubes & hoses4) Vulcanized Rubber + Carbon tyres /air craft tyres (to maintain their elasticity