What is Pressure Sensitive Adhesive?

Pressure sensitive adhesive (PSA) can be used in a variety projects and can have remarkable results when applied correctly.  According to, Pressure Sensitive Tape Council, PSA is an aggressive and permanently tacky substrate that adheres with finger or hand pressure and exerts a strong holding force (pstc.org).

Two groups of PSA are: double coated carrier based tapes and free film transfer tapes/laminating adhesive.  Double-coated carrier-based tapes are thicker, less conformable, easier to dispense, lower temperature resistance and reinforces substrate.  Free film transfer tapes/laminating adhesive are thinner, more conformable, more difficult to dispense, higher temperature resistance and doesn’t reinforce substrate.  Carriers are provided for double-coated carrier-based tapes where free film transfer tapes/laminating adhesive do not have this.  There are different carrier types, which are: tissue, paper, polyester, polypropylene and foam.  Each are used for different applications, but all serve a similar function.  They help to stabilize the adhesive, improve handling, add thickness, provide removability and provide a barrier between the adhesive.  Release liners can also be added as a protective covering for the adhesive to prevent “unwanted” adhesion and contamination of surface during shipping and handling.

PSA categories can be broken down further into different chemistry categories: rubber PSA (indoor), acrylic PSA (outdoor) and silicone PSA (wide temp).  Each one is better for different environments.

Rubber PSA is adequate for short term, non-critical applications.  This PSA is made from natural or synthetic rubbers which are made tacky by mixing them with various compounds.

Acrylic PSA is great for long term, durable applications.  This PSA is a combination of acrylic monomers and other compounds, formulated to create specific chemical structures which are tacky.

Silicone PSA is suitable for long term, critical applications.  This PSA is made of polymers with an inorganic backbone and organic side groups that are especially formulated for premium performance.

The dwell time allows the adhesive to “flow” into the peaks and valleys of the mating surface or substrate and there’s no curing process.

What affects PSA application?

There are many factors that can affect the effectiveness of a PSA application.  First is surface, which includes: texture, contour, energy and contamination. Second is environment, which includes: solvents/chemicals, temperature exposure and UV light exposure.  Lastly application, time, temperature and pressure.

How do you measure adhesion?

Adhesion is about the bond between the PSA and the mating surface.  Adhesion can be measured by a test method called the peel test (PSTC or ASTM).  Peel values indicate how strongly the PSA has bonded, or adhered, to a substrate.  Initial adhesion indicates how well a PSA has bonded to a substrate after a short period of time, usually seconds or minutes.  Ultimate adhesion refers to a PSA’s bond strength after 72 hours.  Both initial and ultimate adhesion are measured by the peel test.

How do you measure cohesion?

Cohesion is about the internal strength of the PSA film itself.  Cohesion can be measured by a test method called shear test (PSTC or ASTM).  Shear values then indicate the internal strength of an adhesive.  Adhesives with higher shear values (which equates to stronger cohesion) will withstand exposure to higher temperatures and chemicals.