Foamed silicones for compression joints production
Compression seals are flexible materials, that are easily deformable materials when exposed to mechanical stress. Once compressed, the joint deforms itself, fills the gap between the assembled parts and then plays a role of sealing barrier.
This type of gasket (often called CIPG, for Cure-In-Place Gasket) is particularly used when the assemblies are regularly opened and closed (for maintenance operations, for example): when reopening, the compressed gasket comes back to its initial shape, and can be compressed again thereafter.
Dow Corning and Samaro now offer foamed silicones specially formulated for the production of compression joints.
Expandable silicones (also known as DFGs for Dispensed Foam Gaskets) are fluid bicomponent products. Once the two components are mixed and dispensed in a groove using a robot, the silicone swells rapidly (by generating dihydrogen gas) and forms in a few minutes a cellular foam (comprising about 70% of open cells ).
– Mixing the two components
– Room temperature curing, swelling of the foam
– Fully cured silicone foam
The obtained gasket has a very low hardness (Shore 00 hardness value between 25 and 70), is easily compressible and requires only moderate tightening forces. The optimum compression ratio for achieving a good sealing with this type of products is between 45% and 55%.
– T=0 : Mixing/dispensing
– 3 min = Start of the chemical reaction
– 3 to 10 min : foaming of the silicone
– 10 min = skin formation
– 15 min = assembly
Foamed silicones from Dow Corning are either self-leveling (very fluid, for application on flat surfaces) or have reduced flowability (“RF “, for applications on slightly inclined surfaces).
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