1. Heat Resistance

Compared to organic rubbers, silicone rubbers in general have incomparably high heat resistance.
Silicone rubbers can be used simi-permanently at 150C (302F) with almost no change in the properties and can withstand more than 10,000 hours of continued service at 200C (392F).With this excellent heat resistance, silicone rubbers are widely used in application requiring excellent heat resistance.
Heat resistance of general purpose silicone rubbers may differ considerably depending on the formulation of the ingredients, selection of the curing agent, etc.
 

2. Cold Resistance

Silicone rubbers have excellent cold resistance. In contrast to brittle point of most organic, silicone rubbers can retain their elasticity, where most of other organic rubbers lose their elasticity and become brittle.

3. Weather ability

Silicone rubbers have excellent weather ability. While rapid degradation is unavoidable in most organic rubbers under the influence of ozone, produced by corona discharge, silicone rubbers are virtually unaffected by ozone. Moreover, physical properties of silicone rubbers are stable and little changed even by prolonged exposure to ultraviolet light and over weathering conditions.

4. Electrical Properties

5. Electrical Conductivity

Silicone rubbers can be electro conductive by compounding with a filer such as carbon black. Several grades of electroconductive silicone rubber are available.
Applications of electroconductive silicone rubbers include contact points of keyboards, parts in electrical heater elements, parts in antistatic devices, and shielding of high voltage cables.

6. Radiation Resistance

Although the radiation resistance of diethyl silicone-based general-purpose silicone rubbers is not particularly high compared to most organic rubbers, methyl phenyl silicone rubbers ,formulated from a silicone gum having phenyl groups introduced into the polymer molecules, have greatly improved radiation resistance and are useful as a material for electrical insulation of cables and connectors in atomic power plants.
Silicone rubbers can be used as a radiation-resistant material even at high temperature as high as 200C (392F) to 300C (572F) , where most organic rubbers such as mature rubber can no longer be used due to thermal degradation.
Silicone rubber have a thermal conduct

7. Thermal Conductivity

vity of about 0.5 * 10-3 cal/cm-sec C. this value is higher than that of most organic rubbers.
Thermal conductivity property of silicone rubbers are used in heat-radiator sheets, EMI gasket and heating rollers.

8. Steam Resistance

Silicone rubbers absorb a maximum of about 1% of water even after prolonged immersion in water. Mechanical and electrical properties of silicone rubbers are little affected by immersion irrespective of water temperature.
Although no degradation is seen in silicone rubbers in contact with steam under normal pressure, pressurized steam may have considerable influences on the properties of silicone rubbers. High pressure steam at 150C (320F) or higher causes breakage of the polymeric main chain of the organic polysiloxane so that the properties of the silicone rubber are reduced. This problem can be solved by the improvement in the formulation of the silicone rubber and selection of the proper curing agent and post curing conditions.

9. Chemical, Oil, and Solvent Resistance

Chemical, Oil, and Solvent Resistance
At temperature below 100C (212F), the oil resistance of silicone rubber is somewhat inferior to that of nitride and chloroprene rubbers. At temperature above 100C (212F), the oil resistance of silicone rubber is superior to all types of organic rubber.
Silicone rubbers are chemical and solvent resistant as will. Polar organic compounds such as aniline, alcohol, dilute alkaline and acid solutions only slightly affect the properties of silicone rubber exhibiting a maximum swelling of 10-15©‡.
Silicon rubber swells when contacted with moon-polar solvents such as benzene, toluene,
and gasoline but he original properties are quickly restored when the solvents are removed.

Silicone should not be used with highly concentrated strong acid and alkaline solutions because they permanently damage silicone rubber.
Other solvents affect the properties of silicone rubber in different ways so it is important to thoroughly test silicone rubber before using in areas where solvents are being used.

10. Compression Set

Compression set is critical when rubber is used as a packing material in pressure cookers and other high pressure applications. The compression set of silicone rubber is very low and varies little in temperature from -60C (76F) to 250C (482F).On the other hand, organic rubbers are not suitable for use as packing materials at this extreme temperature.

11. Bending Fatigue

Conventional rubbers are generally not as resistant as organic rubbers against dynamic stress such as fatigue by repeated bending.
Compounded rubbers which are 8 to 20 times as resistant against fatigue by bending compared to conventional grades of silicone rubbers.
There silicone rubbers products are used in keyboards in office automation instruments, rubber-made parts of transportation machines, and other applications where repeating flexing and bending are required.

12. High Tear Strength

General purpose silicone rubbers have a tear strength of about 15 kgf/cm. This relatively low tear strength can be substantially increased by improving the chemical structure of the organopolysiloxane and selecting the proper curing agent and filler.
Several high-strength grades with a tear strength of 30-50 kgf/cm are available and are widely used for molding intricately shaped, reverse-taper, and large-sized articles.
Although silicone rubber generally has a lower strength than organic rubber, at high temperature silicone rubber retains its strength whereas organic rubber's strength gradually deteriorates.

13. Gas Permeability

Thin films of silicone rubbers have somewhat larger permeability to gases and vapors than organic rubber and plastic resin films. Relatively high selectivity of permeability among different gases is also one of the characteristic features of silicone rubber films. By virtue of these unique features, silicone rubber films are promising as a membrane for the separation of gases and liquids.
For example, heart-lung machines and oxygen enrichment are now being developed using silicone rubber films as the gas exchange membrane.

14. Vibration Absorption

General purpose silicone rubbers have a small loss factor so that they are not recommended as a vibration-proof material. However, several vibration-proof silicone products are available which serve as a vibration-proof material with stability over a temperature range from -50C (-58F) to 100C (212F).

15. Transparency and Coloration

In contrast to most organic rubbers colored in black due to the formulation of carbon black as a reinforcing filler, silicone rubbers can be highly transparent when the filler compounded for the reinforcement is a finely divided silica filler which only slightly affects the transparency inherent in organopolysiloxane gum.
Several high-transparency, high-strength silicone rubber products are used to make various shaped articles such as tubes for and food-processing machines.
High-transparency silicone rubber compounds can easily be colored by adding a pigment.
Vividly and brilliantly colored silicone rubber articles can be manufactured.

16. Non-Stickiness and Corrosion Resistance

Silicone rubbers are chemically inert and as such are non corrosive to most metals and other materials. Silicone rubbers also have excellent release properties making them ideal for use as flexing rollers in copying machines, rollers in printing presses, sheets and lost wax processes.