There are two basic types of rubber used in the rubber industry: natural and synthetic. A number of different synthetic rubber polymers are used to make a wide variety of rubber products (see table 1). Natural rubber is mostly produced in Southeast Asia, whereas synthetic rubber is mostly produced in the industrialized countries—the United States, Japan, Western Europe and Eastern Europe. Brazil is the only developing country with a significant synthetic rubber industry.
Table 1. Some important rubber polymers
|
Type of rubber/ |
Production |
Properties |
Common uses |
|
|
Natural rubber |
Thailand |
1,501 |
General purpose; not oil-resistant, swollen by solvents; subject to weathering by oxygen, ozone, |
Tyres, shock mounts, seals, couplings, bridge and building bearings, footwear, hoses, conveyor belts, moulded products, linings, rolls, gloves, condoms, medical devices, adhesives, carpet backing, thread, foam |
|
Polyisoprene (IR) |
US |
47 |
General purpose; synthetic natural rubber, similar properties |
See natural rubber above. |
|
Styrene-butadiene (SBR) |
US |
920 |
General purpose; Second World War natural rubber substitute; poor oil/solvent resistance |
Tyres (75%), conveyor belts, sponge, moulded goods, footwear, hoses, roll coverings, adhesives, waterproofing, latex carpet backing, foam products |
|
Polybutadiene (BR) |
US |
465 |
Poor oil/solvent resistance; subject to weathering; high resilience, abrasion resistance and low |
Tyres, shoes, conveyor belts, transmission belts, toy superballs |
|
Butyl (IIR) |
US |
130 |
Low gas permeability; resistant to heat, acid, polar liquids; not resistant to oil, solvents; moderate weathering |
Inner tubes, tire curing bladders, caulking and sealants, cable insulation, vibration isolators, pond liners and roofing membranes, |
|
Ethylene-propylene/ |
US |
261 |
Low-temperature flexibility; resistant to weathering and heat but not oil, solvents; excellent electrical properties |
Wire and cable jackets; extruded weather stripping and seals; moulded products; isolation mounts; liner sheeting for grain storage, roofing, ponds, ditches, landfill |
|
Polychloroprene (CR) |
US |
105 |
Resistant to oil, flame, heat and weather |
Wire and cable jackets, hoses, belts, conveyor belts, footwear, wet suits, coated fabrics and inflatable products, extrusions, adhesives, |
|
Nitrile (NBR) |
US |
64 |
Resistant to oil, solvents, vegetable oil; swollen by polar solvents such as ketones |
Sealants, fuel-resistant hose linings and gaskets, roll coverings, conveyor belts, shoe soles, gloves, adhesives, oil-drilling equipment |
|
Silicone (MQ) |
US |
95 |
Stable at high/low temperatures; resistant to oil, solvents, weathering; physiologically and chemically inert |
Wire and cable insulation, seals, adhesives, gaskets, specialty moulded and extruded goods, gas masks and respirators, food and medical tubing, surgical implants |
|
Polysulphide (OT) |
US |
20 |
Resistant to oil, solvents, low temperature, weathering; low gas permeability |
Roller covering, hose liner, gaskets, moulded goods, sealants, gas meter diaphragms, glass sealants, solid rocket propellant binder |
|
Reclaimed rubber |
– |
– |
Shorter polymer chains; easier processing; less mixing time and power consumption; lower tensile strength and lower cost |
Tyres, inner tubes, floor mats, mechanical goods, adhesives, rubberized asphalt |
Source: Production figures abstracted from Stanford Research Institute data.
Tyres and tyre products account for approximately 60% of synthetic rubber use and 75% of natural rubber consumption (Greek 1991), employing about half a million workers worldwide. Important non-tyre uses of rubber include automotive belts and hoses, gloves, condoms and rubber footwear.
In recent years, there has been a globalization of the rubber industry. This labour-intensive industry has grown in developing countries. Table 2 shows worldwide natural and synthetic rubber consumption for 1993.
Table 2. Worldwide rubber consumption for 1993
|
Region |
Synthetic rubber |
Natural rubber |
|
North America |
2,749 |
999 |
|
Western Europe |
2,137 |
930 |
|
Asia and Oceania |
1,849 |
2,043 |
|
Latin America |
575 |
260 |
|
Central Europe |
215 |
65 |
|
Commonwealth of Independent States |
1,665 |
100 |
|
Middle East and Africa |
124 |
162 |
|
China and Asia* |
453 |
750 |
|
Total |
9,767 |
5,309 |
*Includes China, North Korea and Viet Nam.
Source: International Institute of Synthetic Rubber Producers 1994.