Elastomerics Blog

Fabricated gaskets, room temperature vulcanizing (RTV) gaskets, and form-in-place (FIP) gaskets can all be used to seal the spaces between mating surfaces. Each has its advantages, but there are  disadvantages and tradeoffs to consider. In addition to gasket installation or application, engineers need to evaluate material and performance properties. There can also be some confusion about related terms like solid gaskets and liquid gaskets. This blog post from Stockwell Elastomerics explains what engineers need to know.

Fabricated Gaskets

Fabricated gaskets can be made of solid, sponge, or foam materials. Typically, these materials are elastomers like silicone, urethane foam, EPDM and other similar materials.  When gaskets are fabricated from sheets, rolls, or extrusions, there isn’t a phase change from a liquid to a solid. Instead, non-liquid material is cut into a specific size and shape from roll or sheet goods. Even with sponge gaskets and foam gaskets, customers receive a product that’s fully cured in form.

To provide sealing, gaskets fill the gaps between mating surfaces such as a door and a door jamb. Gasket compression is critical, but too much compression can prevent the gasket from returning to its original dimensions when this force is removed, such as when a door is opened. Typically, assembly personnel install and replace gaskets by hand. Molded or extruded gaskets may press into place over an edge, but gaskets made from sheet materials may attach with adhesives and/or fasteners instead.

Benefits:

• Minimal setup – tool-less cutting machines are set up in minutes and making parts before other processes have had the tools installed
• Ability to service enclosures – having the gasket fully cured allows opening of enclosures, servicing as needed.
• Resilience (depending on the material choice) – gaskets made from silicone and a few other high performance materials offer compression set resistance; they will spring back to original form
• Long shelf-life

Trade-offs:

• For large gaskets, they can be cost prohibitive. There are options, such as dovetail gaskets.
• Not always easy to spec in. Applications Engineers at Stockwell Elastomerics can work with customers to help with this specification.

RTV Gaskets

RTV gaskets are made of a silicone elastomer that’s supplied as a liquid and applied to a surface where the material hardens at room temperature but remains flexible. Known as curing or vulcanization, this cross linking process causes the RTV silicone to obtain its final properties. During product assembly, RTV gaskets can be applied by hand or dispensed with equipment. Either way, an RTV gasket conforms to the surface, supports some amount of compression, and facilitates sealing and assembly in a single step.

Unlike traditional gaskets, RTV is only available in silicone. These gaskets always require curing. In their liquid state, RTV silicones are susceptible to picking up dirt. If too much RTV is applied to a substrate, excess material may seep onto surfaces where it doesn’t belong or break off after curing. Although RTV gaskets don’t require adhesives or fasteners, removing them can be challenging because they are intended for permanent installation.

Benefits:

• Often can achieve highest strength bonding
• Can be customized for fast or slow working times, with or without heat, etc.

Trade-offs:

• It’s messy – like working with silicone caulk, these can be difficult for companies not experienced.
• Curing mechanisms (catalysts) can cause issues in other processing, and conversely are also sensitive to factory environment/impurities.
• Shelf life sensitive – shelf life varies from 3 months to 1 year
• No re-workability

FIP Gaskets
Form-in-place (FIP) gaskets are made of a silicone, or synthetic rubber that is supplied as a liquid and dispensed onto a surface where the material is cured with heat, moisture, or ultraviolet light. Unlike RTV gaskets, which are sometimes applied by hand, FIP gaskets are always dispensed using purpose-built CNC equipment. This limits the practical applications of FIP gaskets to higher volumes, such as the sealing and assembly for enclosures such as consumer electronics.

Among their advantages, FIP gaskets can fill small or complex spaces that are difficult for installers to reach or for other types of gaskets to accommodate. When applied properly, form-in-place materials produce little waste and can achieve precise dimensions. Because bead size is a practical limitation, conventional gaskets are a better choice. Like some traditional gaskets and RTV gaskets, however, FIP gaskets can be made of electrically conductive silicones that provide EMI shielding.

Benefits:

• Can make large gaskets and very small gaskets
• Cost effective for high volume

Trade-offs:

• Long setup and troubleshooting – best for very high volume
• Bead sealing quality – depending on geometry, the bead can affect sealing
• Shelf life on the uncured material
• No re-workability
• Requires special equipment and assembly onto housings. If process not dialed in, fallout can be expensive

Contact Stockwell Elastomerics for more information or to request a quote for custom gasket manufacturing services.