Pressure Sensitive Adhesive (PSA) Tape Selection Considerations
As we know in our industry, it is critical to help end user customers understand the materials they want to bond together and the application operating environment when choosing a pressure-sensitive adhesive (PSA) tape for applications. The level of adhesion, bond strength, and durability will vary depending on the combination of substrates and the type of PSA tape you choose.
Here are five important questions to ask before selection:
How rough is the surface texture?
The adhesive tape you choose depends on the roughness of the surface. Smoother surfaces can be easily bonded with a thinner adhesive, but rougher, irregular surfaces can require a thicker adhesive that has a better flow. Firm adhesives or very thin adhesives may not wet into the surface of a material, failing to form a secure bond if one or more of the substrates has a rough or uneven surface. Instead, such surfaces require PSA tapes with a thicker layer of soft, viscoelastic adhesives that flow into the smallest valleys of a surface. The flow of the adhesive, given ample dwell time, is enough to securely form a bond between two rough surfaces.
Choosing the right thickness and flow of your adhesive is a matter of starting with a few good candidates and testing them out on the surfaces being bonded to see which tape provides the optimal bond.
What is the contour of the surface?
The contour of the surface directly impacts the type of tape that will be most effective. Similar to surface texture, it decides the thickness and firmness of the tape that should be used. Running pressure-sensitive adhesive tape along a flat surface differs greatly from running it along a contoured surface. The greater the curve, the more flexible the tape will need to be in order to correctly bond to the surface. Depending on the rigidity of the secondary surface, the tape thickness becomes an important consideration as well. If the tape is too thin or firm, it can cause internal stress on the tape and/or minimize surface contact (resulting in tearing) and flagging (lifting at the edges). A thicker, more flexible tape with a softer adhesive allows for maximum surface contact and bond strength.
What is the surface energy of the substrate?
A substrate’s surface energy is a relative measurement of the excess energy on the surface of a material, and its importance in the bonding process cannot be understated. The surface energy of a particular material mainly affects the wetting of the adhesive on PSA tape. This phenomenon is how quickly and how much the adhesive spreads out on the bonding surface, affecting the strength of the attraction. The higher the surface energy the greater the attraction, which in turn causes more wet out, meaning the surface is easy to adhere to. Conversely, the lower the surface energy, the lower the attraction and the less the PSA wets out the substrate.
This PSA tape is laminated directly onto a removable liner. It bonds well to most substrates, including difficult- to-bond low surface energy plastics and powder coated paints.
This PSA tape is laminated directly onto a removable liner. It bonds well to most substrates, including difficult- to-bond low surface energy plastics and powder coated paints.
High-surface-energy materials that have an excellent adhesive wet-out include:
- Aluminum
- Copper
- Stainless Steel
- Tin
- Glass
- Porcelain
Medium-surface-energy materials, including a range of plastics and paints, typically demonstrate very good adhesive wet-out, such as the following:
- PVC
- Acrylic
- Nylon
- Polyester
- Polyurethane or epoxy paints
- Kapton (polyimide film)
- Phenolic
- ABS
Low-surface-energy materials are harder to adhere to because the attraction is not as strong. Low-surface-energy materials with poor adhesive wet-out include:
- Polystyrene
- Polyvinyl acetate
- Acetyl
- EVA
- Powder paints
- Polyethylene
- Polypropylene
- UHMW
- Tedlar (PVF)
- Teflon
The material surface energy will dictate what PSA will provide an adequate bond to your substrates.
Read more about Adhesive Technologies on adhesives.org.
Source: Adhesives Magazine | Engineered Materials, Inc.