Gaskets are usually inexpensive to purchase but play a crucial role in the devices they are present in. A gasket’s primary role is to provide a strong seal to a gas or liquid throughout the life cycle of a device. Efficient design of gasket is required since it covers up for any imperfections in the mating material.
Though gasket applications vary to a great deals, some commonalities between them should be analyzed to make sure the seal serves its purpose in the device.
The following key parameters need to be considered while selecting the material for gasket:
Temperature is one of the many key factors affecting material selection. Temperature can alter various properties of gasket material, for example stress level and maximum tolerance of the material to temperature. Internal and external temperature both should be considered while performing stress testing. Gaskets may also face large variations in temperature from very high temperatures to low freezing temperatures. Thus determining the range of temperature variation is also very essential in material selection.
If the pressure level exceeds and gasket is weak, it may completely break. Thus pressure and temperature both are considered as key parameters to judge suitability of a gasket material.
Media stands for the liquid or gaseous component that the gasket is sealing. Once a suitable material matching the temperature and pressure level is selected, we need to make sure that material doesn’t cause any adverse reaction with the media component. Various chemicals may impact both structural and functional properties of the material.
UV & Ozone:
UV and Ozone may cause degradation of rubber made gaskets. Ozone is found in atmosphere as well as electric set ups. Drying, cracking or hardening would be signs of degradation due to UV.
EMI & RFI requirements:
Gaskets in automotive and aeronautic devices may need to meet several EMI standards for their products. To restrict EMI emitted by wires, they need to be encapsulated in conductive materials Thus to fulfil this requirement gasket material should be conductive in nature.
For food industry, other standards such as provided by the FDA would also be need to be satisfied.
A variety of material options are available to design and make gasket from:
Elastomers are the most commonly found materials and are also quite affordable and readily available for purchase.
Plastics, especially engineered plastics are also a favored choice. They possess characteristics that are suitable to almost all devices that require a gasket seal.
Other than these two, Cork is also a popular choice. Its properties such as water and severe temperature fluctuation resistance prove it to be suitable for gaskets.
A combination of Cork and rubber which is made with granular cork and synthetic rubber polymer is also preferred as a gasket due to its high resilience and flexibility.
Foam can be used for gaskets too since it is made of several components. According to the cellular make up of the material, open or closed cell foam can be used. Usually open cell foams are preferred for light industrial applications and closed cell foam is used in cases when higher resistance to heat or UV is required. It is more stable in nature as compared to open cell foam.
Another option for gasket material would be sponge made with various manufacturing and curing procedures. Sponge too comes in two varieties of open cell and closed cell sponge. Unlike foam, sponge is used for more heavy duty purposes.
In general, depending on the medium, the gasket material should have following properties :
Impermeable: Material must not allow any kind of leakage even when exposed to high pressure.
Resilience and Strength: Must adapt itself according to all irregularities on flange surfaces and provide sufficient tensile strength to resist blow-out under operating conditions.
Creepage: Must not spread under high bolt pressure or high contained fluid pressure – even at high temperatures.
Chemicals: Must not be weakened by a wide range of fluids even when exposed for extended periods at high temperatures.
Temperature: Must remain robust for long periods of time at low or high temperatures.