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NATURAL AND SYNTETIC RUBBER, recyclable like plastic, :check: tensile…
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- displays elastic properties
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- vulcanize to become insoluble and infusable
- naturally occurs in the sap of the rubber tree
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- prepared from latex(Colloidal Solution of Rubber in Water)
- polymer of isoprene (2-Methyl -1, 3 - Butadine)
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- 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)
- the process takes around 6 hours at 140°C
- Accelerator increases the speed of vulcanization
- sulphur vulcanization principal stages:
- mixing of crude rubber with about 5-30% of sulfur
- molding the rubber mixture
- heating the mixture to 250-400°F
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- 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
- 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
- Poly(styrene butadiene styrene)
- Polystyrene is a tough hard plastic, and Polybutadiene is rubbery
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- obtained by the free radical polymerization of isoprene
- has all trans-configuration
- has a highly regular zig zag chain which cannot be stretched.
- 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
- 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