Silicone information

Silicone information

Features of Silicone Rubber

Heat resistance

The C-C bond energy, which is the main axis of organic synthetic rubber, is 83 kcal/mol, while the Si-O bond energy is 108 kcal/mol. This difference in bond energy results in excellent heat resistance of the silicone rubber. The serviceable temperature of silicone rubber is usually 150-250℃, and if used intermittently for a short period of time, it can be up to 350℃.

Application examples : Packing and gasket of various internal combustion engines such as hose and boots. Microwave ovens, pressure cookers gaskets, coffee pods, etc., And heat-resistant packing for automobiles.
Continuous useable time of silicone rubber by temperature

Low temperature flexibility

The cold resistance of silicone rubber is the best of all kinds of rubber. The saturation point of general organic rubber is -20℃ to -40℃, whereas silicone rubber is -60℃ to -70℃, so it maintains elasticity almost unchanged even at low temperatures when general organic rubber is shock-destroyed, and silicone rubber (PVMQ) containing phenyl groups in the side chain can be used at such ultra low temperature up to -100℃.

Application examples : Aircraft and spacecraft parts, automotive parts and gaskets in severe cold areas, parts in refrigerators and refrigeration facilities, gaskets, packing.

Weather resistance

Unlike other organic rubbers, silicone rubber does not have double bonds that react with oxygen, ozone, and ultraviolet rays in the atmosphere in its molecular structure to cause cracks, so it has excellent weather resistance and little change in physical properties even when left outdoors for a long time.

Weather resistance of silicone rubber by appearance inspection

Compression set

The compression set of organic rubber increases significantly with temperature changes, while silicone rubber maintains elasticity and resilience in a wide temperature range from -100℃ to 250℃, which is excellent even when compressive deformation is required under extreme conditions.

Oil resistance

Silicon rubber has excellent oil resistance at high temperature, where ordinary organic rubber other than organic fluoro-elastomer cannot be used.

Application examples : Parts of various internal combustion engines such as oil seal, O-ring, Diaphragm, etc., Check valve

Chemical resistance and steam resistance

Silicon rubber has excellent chemical resistance and is rarely infringed by polar organic compounds such as acids and alkalis. But concentrated acids and alkalis may infringe the properties of silicone rubber. Silicone rubber is stable after being immersed in water for a long time and in contact with steam. It may be decomposed by superheated steam, but can be improved by selecting an appropriate curing agent or curing condition, etc.

Application example : Packing of steam iron, chemical equipment, rice cookers, etc
Chemical resistance of silicone rubber (after 168 hours immersion at 25℃)
Oil resistance of silicone rubber (VMQ)
Heat Resistance and Oil Resistance of Various Rubber

Electrical properties

Silicone rubber is widely used as an insulating material because it is resistant to arc or corona discharge under high voltage. The insulating properties come from a unique chemical structure of low carbon ratio in molecules and no carbon black as a reinforcing. On the other hand, there is also conductive silicone rubber that has a volume resistivity of 5Ω-cm or less by mixing conductive fillers such as conductive carbon black.

Application examples: Wire coating, insulation tubing, insulation tape, defroster wire for refrigerator, various heating equipment wires, ignition wire for automobiles, keyboard contacts.
Electrical Properties of Silicone Rubber at High Temperature

Flame retardancy

Silicone rubber does not burn easily because it contains less hydrocarbons than organic rubber due to its molecular structure, and it does not generate toxic gases during combustion.

Application examples : TV anode cap, electrical and electronic components that require flame retardant, rubber sleeves, flame retardant insulated wires
Density of smoke, combustion time, and concentration of toxic gas during combustion of silicone rubber (NFPA TEST METHOD 258-T)

Other features of silicone rubber

The gas permeability of silicone rubber is 30 to 40 times higher than that of organic rubber, so it is also used for special applications such as air purifiers and water separation devices. Silicone rubber is durable against radiation, especially PVMQ based material shows excellent performance. It is transparent and easily pigment-able. It is chemically inert, does not corrode other materials. and has excellent self-lubricating properties. Silicone rubber has lower green strength than organic rubber, so it gives excellent workability.