Pressure-sensitive adhesives (PSAs) are non-reactive, thin, flexible materials that remain permanently viscous and can adhere to a wide array of substrates. Laminating PSAs to materials provides most substrates with additional environmental durability. Web Seal can recommend the most effective PSA for your specific application.
Unlike other adhesives, PSAs do not alter physically from an original liquid state to a solid after the bond is formed. They efficiently adhere instantly to a solid and create an aggressive bond to the substrate material by the application of light pressure, without the need for heat, water or other solvents to activate it. The strength of the bond will depend on the formulation, the substrate, and a number of other factors.
A variety of PSA formulations are available for gaskets, seals and other components, and come in single-sided or double-sided formats and transfer tapes.
With a single-sided PSA, the adhesive is applied to only one side of a backing, or carrier, which is then applied to the gasket or seal. Often, the carrier is treated with a primer or release coating to enable the stability of the adhesive. Double-sided PSAs consist of a carrier that has a coating of adhesive on both sides plus a release liner to prevent the adhesive from sticking to itself. Release liners are commonly made of paper with silicone release agents. Unlike single- and double-sided PSA, transfer tapes are clear adhesives that are directly coated onto a release liner as part of its structure.
Development of Pressure Sensitive Adhesives
Pressure-sensitive adhesives were originally based on natural rubber. Today, that has expanded to include synthetic elastomers and polyacrylate or silicone resins, frequently blended with unique additives. For example, plasticizers and resins can be used to control the range of strength and tack. Where high performance is required, a formulation can increase strength over time when a bonding resin is used, due to the dynamic and uncross-linked chemical nature of the additive. Silicone adhesives offer good adhesion to both low and high energy surfaces and are especially useful for substrates that are more challenging to bond.
These industrial pressure-sensitive adhesives are developed to have strong flexibility, tack and peel strength. More than 50 distinct formulations have been engineered to work effectively with individual types of substrates, including cork, elastomers, fiber, films, foam, metal foils, plastics, sponge, silicone, RFI/EMI and thermal management (TMI) materials.
- Elastomer-based PSAs are the most cost-effective, with medium high tack, adhesion and shear characteristics; not recommended for high temperature use
- Acrylic-based PSAs are mid-range in cost, with higher temperature resistance, good resistance to solvents and environmental conditions, high adhesion and shear, superior UV resistance, and medium tack; recommended for long-term aging
- Silicone-based PSAs are the most expensive, but offer superior shear characteristics as well as exceptional resistance to solvents, temperature, and UVs; only adhesive that bonds properly with silicone substrates
Using PSA-Laminated Gaskets and Seals
PSA can be applied to gaskets, seals and other components on one side, on both sides, or in directly bonding parts together. The same PSA can be laminated to both sides, or two different PSAs can be applied, depending on the application needs. Fabricated parts can be supplied as kiss-cuts or with PSA applied in patterns to provide both bonded and unbonded areas. Release liners are commonly made of paper with silicone release agents.
Using pressure-sensitive adhesive laminated gaskets, seals and other parts:
- Provides ease of assembly and reduction of production time
- Bonds diverse materials together without issues of incompatibility
- Offers seamless surface-to-surface bonding
- Excludes moisture
- Provides noise and vibration reduction
- Enhances appearance by eliminating the need for visible or bulky fasteners
- Offers stability during transport, storage and assembly