Silicone gaskets are a type of gasket made of silicone (a synthetic rubber comprised of silicon, oxygen, carbon, hydrogen and, in some but not all cases, other additives). Silicone gaskets are not to be confused with other polymer gaskets, which, instead of having a carbon backbone, have a Si-O-Si backbone.
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Applications of Silicone Gaskets
Gaskets are sealing products that fill the space and keep out air and weather in between two mating surfaces. Gaskets all have different applications, depending on the material with which they are made. For silicone gaskets, the most successful applications are those related to consumer products, light industrial needs and medical devices. Examples of applications and settings like these include: temporary food storage containers, sealant for baking materials, waterproofing swim goggles, infusion pumps, dialysis machines and incubators.
Silicone Gasket Design and Customization
Silicone gaskets can be engineered into different silicone grades, each grade reflecting varying qualities and the degree to which said qualities are present. Such properties include flame resistance, heat resistance, steam resistance, chemical/acid resistance, gas resistance and electrical conductivity. There are several special grades of silicone, which are as follow: flame retardant, steam resistant, high tear strength, metal detectable, extreme high temperature, extreme low temperature, chemical/oil/acid/gas resistant, electrically conductive and low smoke emitting. In addition, silicone rubber can be defined by hardness levels, which are arranged on a scale. This scale is expressed as IRDH or Shore A between the numbers of 1 and 10, with 100 being the hardest. Before a silicone gasket is formed, the chosen material can be dyed into any color.
Manufacturing Process of Silicone Gaskets
Manufacturers may perform one of these processes to form a silicone gasket:
Each molding process offers different process speeds and efficiencies and different possible configurations. First, injection molding is a process that uses a molding machine that includes the following components: injectors, metering units, supply drums (or plungers), mixers, a nozzle, and a mold clamp. To work, liquid silicone rubber and a catalyst, each of which is stored in one of the respective supply drums, are pumped at a sustained and constant ratio via the metering units into the mixers. Injecting devices help by pressuring the silicone until they move into the pumping section of the system.
Inside the mixers, which can be static or dynamic, the materials are combined, then driven by pressure into a designated mold. The mold is held securely in place by a mold clamp. Upon completion of the process, the mold clamps open, allowing the newly formed gasket to be removed. Cast molding, or casting, is a simpler process that involves pouring a liquid material into a hollow mold, allowing it to cool and then removing it. Compression molding also involves a mold cavity. However, in this instance, the mold is heated and, after the preheated or liquid silicone is poured in, the mold is covered by a top or plug of some sort. After the mold is covered, applied pressure from the top forces the material inside to cover every area of the mold. The heat and pressure are only removed after the rubber has cured.
Transfer molding is a similar process to compression molding, the main difference being that it starts with an enclosed mold instead of an open mold. Finally, making silicone gaskets via dip molding works just as it sounds. A metal gasket-shaped mold is physically dipped into a vat of fluid or powder silicone. After this, the mold is removed and the new part is allowed to dry.
Points to Consider When Purchasing Silicone Gaskets
As a rule, in the contexts of stress and/or tension, silicone gasket applications must be fairly undemanding. This is because silicone has a relatively low tensile strength as compared to other rubbers, including natural rubber. Many high demand applications are not appropriate for silicone gaskets, as they simply cannot withstand great amounts of tension. By and large, they cannot, for example, be used in automobiles, which tend to put forth large amounts of pressure in the way of compressing, torquing, and frictioning. Silicone does, however, have the ability to work well in the face of temperatures as low as -55 and as high as 300.
To put that in perspective, rubber gasket materials like Viton can begin to break down and exhibit the symptoms of deterioration when the surrounding temperatures are as low as 200. Furthermore, though silicone is not as impact-resistant or tension-resistant as natural rubber, it is much more resistant to ozone cracking and UV rays than natural rubber. Because of its resiliency, silicone gaskets are well-suited to outdoor applications. Silicone gaskets are also well-suited to chemical processing applications and some medical device applications since it is highly chemically inert.