NATURAL AND SYNTETIC RUBBER

INTRODUCTION

RUBBER

THERMOSET ELASTOMER

THERMOPLASTIC ELASTOMER

ELASTOMER

  • elastic polymer
  • displays elastic properties
  • 'rub away'
  • latex original name
  • crosslinked rubber
  • vulcanize to become insoluble and infusable
  • recyclable like plastic
  • no crosslinking

NATURAL RUBBER AND LATEX

NATURAL RUBBER

NATURAL RUBBER (NR) LATEX

  • naturally occurs in the sap of the rubber tree
  • has elastic properties
  • prepared from latex(Colloidal Solution of Rubber in Water)
  • polymer of isoprene (2-Methyl -1, 3 - Butadine) bdjad
  • located in latex vessel
  • cutting the tree bark at angle 30°
  • contain proteins, resinous matter, hydrocarbon and mineral
  • Modification methods: centrifugation, sedimentation, water evaporation thickening and electro decantation.
  • modified to have higher dry rubber content
  • sulphur vulcanization (Charles Goodyear, 1839)

NATURAL RUBBER HARVESTING AND PROCESSING

PROPERTIES OF RUBBER IMPROVED BY VULCANIZATION

VULCANIZATION PROCESS

  • the process takes around 6 hours at 140°C
  • Accelerator increases the speed of vulcanization
  • sulphur vulcanization principal stages:
  1. mixing of crude rubber with about 5-30% of sulfur
  1. molding the rubber mixture
  1. heating the mixture to 250-400°F

✅ tensile strength

✅ elasticy

✅ hardness

✅ tear strength

✅ abrasion resistance

✅ resistance to solvents

SYNTETIC RUBBER

THERMOPLASTIC ELASTOMERS (TPE)

  • processed like thermoplastics
  • moderate elongations and returm to its near original shape
  • Thermolast , Hipex , Copec , For Tec E, Santoprene , Termoton , Arnitel , Solprene , Engage, Hytrel , Dryflex , Mediprene , Kraton , and Pibiflex

THERMOSET RUBBER

BUTYL RUBBER (IIR)

  • Copolymer of isobutylene and isoprene
  • produced by polymerization of 98% of isobutylene with 2%of isoprene
  • Rubber stopper for medicine vials bottles, chewing gum, tire inner tube, used in speakers, sealant for roof repair, insulating glass window, gas masks and other protective clothing

SBS RUBBER

  • Poly(styrene butadiene styrene)
  • Polystyrene is a tough hard plastic, and Polybutadiene is rubbery
  • tends to clump together

TRANS-POLYISOPRENE

  • obtained by the free radical polymerization of isoprene
  • has all trans-configuration
  • has a highly regular zig zag chain which cannot be stretched.

NEOPRENE

  • produced by polymerization of chloroprene.
  • DuPont marketed polychloroprene as Neoprene
  • Neoprene is valued for its high tensile strength, resilience, oil and flame resistance, and resistance to degradation by oxygen and ozone

NITRILE RUBBER (BUNA-N)

  • obtained by copolymerization of 1, 3 Butadiene and acrylonitrile in presence of a peroxide catalyst
  • resistant to the action of petrol, lubricating oils and organic solvents
  • used in making oil seals, hoses, tank linings etc