Acrylic pressure sensitive adhesives account for the majority of pressure sensitive adhesives supplied on gaskets and cushioning pads, and generally withstand temperature ranges of -40° F to 250° F. These are generally available from .002" to .005" thick, supplied on a treated paper or plastic release liner. Stockwell Elastomerics, Inc. regularly laminates acrylics to silicone foam, silicone sponge, PORON® cellular urethanes and a number of other solid and sponge rubber gasketing materials to provide pressure sensitive adhesive backed products.

Listing of Pressure Sensitive Adhesives

Acrylics for high temperature extremes
For operating temperatures up to 300°F and intermittent excursions up to 350°F, we suggest 3M 467 for thin bond lines (.002" thick) or 3M 9485 (.005" thick). Stockwell Elastomerics, Inc. regularly laminates these acrylics to silicone foam, silicone sponge and solid silicone. Proprietary priming systems are utilized to ensure good anchoring of the acrylic adhesives onto silicone products, as acrylics are generally not capable of bonding directly onto silicone rubber.

Acrylics for low temperature applications
Most acrylics harden and lose adhesion at -40°F. The portable communications and data acquisition device industry has requirements for high performance bonding below this range. Stockwell Elastomerics, Inc. has helped to solve low temperature LCD gasket bonding and cushioning issues using 3M 9795B (.005" thick) and 9799 (.010" thick) film supported adhesives. These special acrylic pressure sensitive adhesives have been tested to function below -50°F, and 9795B is pigmented black for light opacity.

Low tack / repositioning adhesives
When a narrow / detailed gasket is specified, sometimes the assembler has difficulty setting it into place on the first attempt. A repositioning adhesive backing, such as 3M 9415 may permit the gasket to be removed, adjusted and reapplied onto the correct location in the housing. Low tack pressure sensitive adhesives will build adhesion strength over time if they are applied to clean surfaces.

Low surface energy pressure sensitive adhesives have been formulated to adhere to powder coated metal surfaces and certain plastics. For long term adhesion, we suggest acrylic adhesives instead of the high tack rubber based adhesives that hold quickly to low surface energy surfaces, but may age and fail in sunlight and weather. We suggest testing the material substrate with pressure sensitive adhesive backing, and starting with 3M 9485 transfer film and 9490LE film supported depending on which construction is preferred.

Film Supported Pressure Sensitive Adhesive or Unsupported Transfer Film Pressure Sensitive Adhesive?
For gaskets with fine details that would benefit from dimensional stability during removal of the release liner in assembly, a Mylar or PET film supported adhesive will aid the assemblers. Film supported adhesives can improve the removal of kiss cut gaskets from the release liner. On gaskets or cushioning pads that may be subjected to shear forces or some heat build-up in the assembled device, a high quality transfer film adhesive may be a better choice. In long term / high temperature shear conditions, separation of the adhesive from the film support may occur over time.

Silicone Based Pressure Sensitive Adhesive
Adhesives are specified for applications that may see temperatures beyond the -40°F to 300°F temperature range. Silicone adhesives are generally more expensive than acrylics, the shelf life tends to be shorter and they have lower adhesion levels on most substrates. However, silicone based adhesives will remain functional from -80°F to 450°F and handle excursions beyond this range. Stockwell Elastomerics, Inc. regularly laminates silicone based pressure sensitive adhesive onto thin solid silicone rubber for flexible LCD adhesive patches, thin silicone sponge for gaskets in fuel cell assemblies and aerospace requirements.

The silicone based pressure sensitive adhesives recommended by Stockwell Elastomerics, Inc. are film supported constructions. From our experience, the unsupported silicone adhesives lose too much shelf life when applied to many silicone substrates, due to the cross-linking of the free silicones in the adhesive and the cured silicone substrate. The film support provides a barrier and from our experience, extends the shelf life. For extreme temperature requirements we suggest evaluating AR8458, a silicone adhesive with a high temperature Ultem® polyethermide film carrier. A lower cost alternative is D644, which has a Mylar film carrier. 3M 9731 is a film supported adhesive with one side acrylic and the other side is a silicone based adhesive, often used by Stockwell Elastomerics, Inc. for bonding directly to molded silicone rubber gaskets.

Pressure Sensitive Adhesives with Special Properties
Electrically Conductive Pressure Sensitive Acrylic Adhesives are available for EMI Shielding Gaskets and ESD grounding of conductive cushioning pads. 3M 9713 is a thin acrylic adhesive containing a highly conductive metallized non-woven fabric. Stockwell Elastomerics, Inc. laminates 9713 onto nickel-graphite filled silicone and silver filled silicone for EMI shielding gaskets. AR8002 is a carbon filled acrylic adhesive impregnated into a non-woven carrier for low level EMI shielding and ESD grounding. Stockwell Elastomerics, Inc. laminates AR8002 onto Flectron® metallized fabrics for EMI Shielding, and conductive neoprene and conductive sponges for gaskets and pads requiring ESD protection.

Thermally conductive acrylic adhesives are filled with ceramic particles to enhance thermal transfer. Stockwell Elastomerics, Inc. laminates St. Gobain TR3 thermally conductive acrylic adhesive (.002" thick) onto thermally conductive silicone rubber for gaskets and pads that promote heat transfer.

3M VHB (Very High Bond) Acrylic Foam Adhesives are available from Stockwell Elastomerics, Inc.'s inventory from .015" to .045" thick. Acrylic foams provide high strength, flexible bonding substrates for adhesive patches and gasket applications from -40°F to 250°F. Stockwell Elastomerics, Inc. can laminate these adhesives onto large rubber pads or apply release liners and die cut gaskets and adhesive pads.

The choice of pressure sensitive adhesive can be as important as the gasket or cushioning material specified. When your design is approaching completion, you may request samples from our listing of Most Frequently Specified Adhesives, laminated to your solid or sponge rubber substrate of choice.

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