Chapter 12 rubbers

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Chapter 12 rubbers

  1. 1. NATURAL RUBBER…
  2. 2. NATURAL POLYMERS POLYMER MONOMER1. PROTEIN AMINO ACID2. CARBOHYDRATE GLUCOSE3. NATURAL RUBBER ISOPRENE4. STARCH GLUCOSE5. CELLULOSE GLUCOSE
  3. 3. NATURAL RUBBER
  4. 4. POLYMERIZATION OF RUBBER
  5. 5. PROPERTIES OF NATURAL RUBBER
  6. 6. COAGULATION OF LATEX
  7. 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. 8. VULCANIZATION OF RUBBER DEFINITION:Process for hardeningrubber by treating it withsulphur compound.PURPOSE : To improves thequalities/weakness ofnatural rubber(unvulcanized rubber)
  9. 9. COMPARING AND CONSTRAST THE PROPERTIES OF VULCANIZED & UNVULCANIZED RUBBER
  10. 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. 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. 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

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