Proper Surface Preparation for Strong PSA Tape Bonds
Pressure-sensitive adhesive (PSA) tapes may be one of the best bonding solutions for applications across many industries, but they must be applied properly to achieve the strongest and longest lasting bond possible. Thankfully, PSA tapes are easy to apply, requiring little training, no special tools, and (in most cases) simple surface preparation. Still, surface preparation is important, and this detailed guide will help you achieve the best bond possible with every piece of adhesive tape you apply.
How Pressure-Sensitive Adhesive (PSA) Tapes Work
PSA tapes are adhesive tapes that form a bond when (often minimal) pressure is applied to join the adhesive with the substrate. They do not require multiple components, solvents, heat activation, or extensive cleanup.
PSA tapes are commonly used in:
The automotive industry for mounting trim, emblems, and sealing components.
Electronics for bonding components, heat sinks, and EMI/RFI shielding.
Medical devices for skin contact applications, securing sensors, and medical device assembly.
The construction industry for insulation, glazing, HVAC, and joining a variety of building materials.
Appliances for heat shielding, noise reduction, and vibration dampening.
The aerospace industry for protection, anti-slip protection, and interior mounting.
Furniture assembly for attaching panels, cushioning, etc.
The Importance of Surface Preparation in PSA Tape Application
If you want to achieve a durable bond with PSA tapes, proper surface preparation is critical. Improper preparation can lead to weak bonds, peeling, and adhesive failure, and compromising the integrity of the products in which the PSA tapes are used.
There are many potential Issues with that can occur with improper surface preparation:
Weak Bonds: inadequate adhesion reduces the load-bearing capacity of the bond.
Peeling: poor initial contact or surface contamination can cause the tape to peel away.
Failure: if the surface is not properly prepared, the bond can outright fail and the substrates separate.
How to Properly Prepare a Substrate for PSA Tape Application
Choose the Right Tape
Proper tape application begins with asking the right application questions prior to selection. For example, selecting the appropriate PSA tape for the substrates being bonded. There are many different types of surfaces, and there are many different types of PSA tapes that are specifically tailored to adhering to them. The chemical and physical composition of acrylic PSA tapes is very different than rubber and silicone, and there are many types of specialty tapes that can be used in very specific applications. Consider the tape's compatibility with the surface material, the environmental conditions in which the tape will be operating, and required bond strength that you need based on your application.
Make Sure the Surface is Dry and Free of Oils and Contaminants
Surface contaminants prior to bonding can significantly affect the adhesive's ability to bond properly with the substrate.
The effects of moisture on PSA tape adhesion include:
Reduced Adhesion: moisture can severely impair the adhesion of PSA tapes. Water molecules can infiltrate the adhesive layer, weakening the bond between the adhesive and the substrate. This is particularly problematic for applications where the bond must withstand varying environmental conditions.
Hydrolytic Degradation: certain adhesives are prone to hydrolytic degradation when exposed to moisture. This chemical breakdown of the adhesive matrix can lead to loss of cohesion and adhesion over time.
Surface Contamination: moisture can carry contaminants that further hinder adhesive performance. Dust and debris suspended in moisture can be deposited on the surface, creating barriers to proper bonding.
Substrate Swelling: in materials like wood, moisture can cause swelling, which alters the surface texture and dimensions, further complicating the bonding process.
The effects of oils on PSA tape adhesion include:
Barrier Formation: oils on the surface of a substrate create a barrier that prevents the adhesive from making direct contact with the substrate. This barrier significantly reduces the initial tack and ultimate bond strength of PSA tapes.
Chemical Incompatibility: oils can react with the adhesive, leading to chemical incompatibilities that weaken the adhesive properties. For example, oils may plasticize the adhesive, reducing its cohesive strength.
The effects of Contaminants on PSA tape adhesion include:
Surface Barrier: contaminants lie on the substrate surface. Whether visible or invisible, they create a barrier that inhibits the PSA from wetting out the microscopic pores of the substrate.
Ultimate Adhesion: any level of contaminants can compromise the buildup of ultimate adhesion. The contaminants surface coverage will dictate the degree to which adhesion is inhibited. Obviously, the more contaminants, the likely lower the percentage of ultimate adhesion achieved.
Consider the Environment
Temperature and humidity can affect adhesive performance. High humidity can introduce moisture, while extreme temperatures can alter the adhesive's properties. Every PSA tape has been tested to perform within a specific temperature range, so make sure to check with the manufacturer or your PSA tape specialist to understand the operating temperature range of any PSA tape you use.
Make sure to apply PSA tapes in controlled environments with moderate temperatures between 59-77°F (15-25°C) and in low humidity (<50%). Only specially designed PSA tapes can bond in temperatures below this range. It’s also important to store your PSA tapes in a cool, dry place, away from direct sunlight, to maintain their adhesive properties.
Best Practices for Applying PSA Tape to Prepared Surfaces
To ensure you will achieve maximum bond strength, it is important that the substrate you are bonding is both clean and dry. Follow these preparation steps:
Clean the Surface: use a clean cloth and a mixture of 50% Isopropyl alcohol and 50% water to clean the surface and another clean cloth to dry the surface. If there is a very heavily oiled surface, an industrial degreaser or aggressive solvent cleaner should be used prior to this cleaning step.
Abrading Option: abrading after the initial cleaning step can improve adhesion by increasing the substrate surface area for the PSA tape. In many cases this step may not be necessary. It is critical to follow up abrasion with step 1, surface cleaning, to remove contaminants.
Adhesion Promoter Option: adhesion promoters used either after cleaning or after cleaning, abrading, and cleaning will often improve both initial and ultimate adhesion. This is especially true for plastics and paints.
Firm Pressure: when applying PSA tape to your substrate, make sure to apply with even pressure. Use a roller or squeegee to apply uniform pressure across the tape. Use consistent, firm pressure along the entire length of the tape. For VHB Acrylic Foam tape, for example, the guidance is at least 15 PSI (100kPa) in roller or platen pressure. Apply the tape slowly and steadily to avoid trapping air bubbles. This will ensure full contact with the surface and maximum bond performance.
Proper surface preparation is essential for achieving strong, durable bonds with PSA tapes. By following these detailed steps, from cleaning and drying the surface to considering environmental factors, you can ensure the best performance and longevity of your adhesive bonds.
Depending on the PSA tape, you can achieve approximately 50% to 80% of your ultimate strength immediately after these steps. Over hours and days, the PSA tape will continue wetting out into the clean substrate and gain more strength until ultimate adhesion is achieved.
Are PSA Tape Primers Necessary?
Primers are particularly useful in improving the bonding performance on challenging surfaces, such as low-energy substrates, uneven textures, or materials prone to contamination. Moreover, if you are bonding to a porous surface, like wood or concrete, these substrates will often need to be sealed to ensure a good bond.
Some types of primers that are compatible with PSA tapes include:
Acrylic Primers: acrylic-based primers are versatile and compatible with many substrates, including metals, plastics, and painted surfaces. They are known for their durability and resistance to environmental factors. An example of this type of primer is the 3M™ Primer 94.
Silane Primers: silane primers are particularly effective on glass and ceramic surfaces. They form a chemical bond with the substrate, significantly enhancing adhesion.
Rubber Primers: rubber-based primers are used to improve adhesion on rubber surfaces. They work well with rubber PSA tapes and are often used in automotive and industrial applications.
Water-Based Primers: these primers are environmentally friendly and suitable for a wide range of surfaces. They are easy to apply and clean up, making them a convenient option for many applications. An example of this type of primer is the 3M™ Adhesion Promotor 111.