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TOPIC 4: NATURAL & SYNTHETIC RUBBER, Picture1 - Coggle Diagram
TOPIC 4:
NATURAL & SYNTHETIC RUBBER
NATURAL
Natural Rubber (NR)
an elastic hydrocarbon polymer that naturally occurs as a milky colloidal suspension (latex)
has elastic properties and it undergoes long range reversible extension
a natural polymer of isoprene. Example: Cis-polyisoprene
Natural Rubber (NR) Latex
located in latex vessels to be founded in various parts of the tree.
a colloid system having the rubber particles dispersed in water
contain small amounts of proteins, resinous matters (including lipids), hydrocarbons and mineral substances
Modification methods: centrifugation, sedimentation, water evaporation thickening and electro-decantation.
Natural rubber harvesting and processing
Sulphur vulcanization
Mixing of crude rubber with about 5-30% of sulfur (cross-linking agent) and other additives
Molding (shaping) the rubber mixture.
Heating the mixture to 250-400ºF (120-200ºC). Increased temperature speeds up the vulcanization process resulting in fast and complete cross-linking.
Properties of rubber improved by vulcanization
tensile strength
Elasticity
Hardness
tear strength
abrasion resistance
resistance to Solvents.
Difference between Vulcanized rubber and Natural
Differences
SYNTHETIC
Synthetic rubber
Thermoplastic Elastomers (TPE)
Thermoplastic polymer that possesses the properties of a rubber
processed like thermoplastics, but their applications are those of an elastomer.
ability to stretch to moderate elongations and return to its near original shape, creating a longer life and better physical range than other materials.
Thermoset Rubber
Butyl Rubber (IIR)
Excellent impermeability, good flexibility
Copolymer of isobutylene and isoprene
SBS Rubber
Poly(styrene-butadiene-styrene), or SBS, is a hard rubber that is used to make soles of shoes, tire treads, and other products where durability is important.
Trans-polyisoprene
Synthetic rubber (trans-polyisoprene) was obtained by the free radical polymerization of isoprene.
formed has all trans- Configuration
Neoprene
a synthetic rubber that are produced by polymerization of chloroprene.
high tensile strength, resilience, oil and flame resistance, and resistance to degradation by oxygen and ozone
Nitrile rubber (BUNA-N)
The name BUNA–N is made up of Bu which indicates 1,3 – Butadiene, NA is for Sodium (Na) and N indicates acrylonitrile.
BUNA-N is resistant to the action of petrol, lubricating oils and organic solvents
Differences between natural rubber and synthetic rubber
Differences
