Why make synthetic rubber?
Synthetic rubber is a rubber-like polymer manufactured from petroleum products rather than tapped from a tree. It was developed to overcome the weaknesses of natural rubber and to guarantee a steady supply. Natural rubber is easily attacked by heat, oxygen, sunlight, oil and organic solvents; many synthetic rubbers resist these much better.
Common synthetic rubbers
- SBR (styrene-butadiene rubber) — made from styrene and butadiene; tough and hard-wearing, used for vehicle tyres and shoe soles.
- Neoprene (polychloroprene) — resists oil, heat and chemicals; used for hoses, gaskets and wet suits.
- Silicone rubber — stable over a wide temperature range; used for seals and medical tubing.
Worked example / 例题
Chloroprene, CH2=CCl−CH=CH2, undergoes addition polymerisation to form neoprene: n CH2=CCl−CH=CH2 → −(CH2−CCl=CH−CH2)n−. The chlorine atoms make neoprene far more resistant to oil and heat than natural rubber, so it is chosen for machine parts that meet oil.
Comparing the two rubbers
| Property | Natural rubber | Synthetic rubber |
|---|---|---|
| Resistance to heat | lower | usually higher |
| Resistance to oil and solvents | poor | often good |
| Oxidation by air | easily oxidised | more resistant |
Key idea / 要点
Both natural and synthetic rubbers can be vulcanised with sulfur to add cross-links, further improving strength, elasticity and heat resistance.
Remember / 记住
- Synthetic rubber is made from petroleum, not latex.
- SBR is used for tyres; neoprene resists oil and heat.
- Synthetic rubbers generally resist heat, oil and oxidation better than natural rubber.