What is Pressure Sensitive Adhesive?

Pressure-sensitive adhesives (PSA) play a crucial role in our everyday lives. They offer a simple yet effective way to bond materials without heat or solvents. PSA can be found in various everyday products, providing consumers convenience and reliability. It can be defined as a permanently tacky substrate that adheres to finger or hand pressure and exerts a strong holding force.

PSA tapes come in two main types: double-coated carrier-based tapes and free film transfer tapes/laminating adhesives. Double-coated carrier-based tapes are thicker, less flexible, and have lower temperature resistance. They are great for applications where the material needs to be reinforced. On the other hand, free film transfer tapes/laminating adhesives are thinner, more flexible, and have a higher temperature resistance. This adhesive is better for applications where the material does not require reinforcement. Double-coated carrier-based tapes are typically provided with carriers, which can be made of tissue, paper, polyester, or foam. These carriers are used for various applications but serve a similar purpose. They help stabilize the adhesive, improve handling, provide removability, and create a barrier between the adhesives. In contrast, free film transfer tapes/laminating adhesives do not have carriers. Release liners are used in double-coated barrier-based tapes to protect the adhesive and prevent it from sticking to unintended surfaces during shipping and handling. 

Types of PSAs

PSA (Pressure Sensitive Adhesive) can be further categorized into chemistry types: rubber PSA, Acrylic PSA, and Silicone PSA. Rubber PSA is suitable for indoor, short-term, non-critical applications. It is made from natural or synthetic rubbers that become tacky when mixed with various compounds. Acrylic PSA is ideal for long-term, durable outdoor applications. It is a combination of acrylic monomers and other compounds formulated to create tacky, specific chemical structures. Silicone PSA is best for wide-temperature, long-term, critical applications. It is made from polymers with an inorganic backbone and organic side groups formulated for premium performance.

What affects PSA application?

Several factors can influence the effectiveness of a pressure-sensitive adhesive application. For instance, the surface’s properties, including texture, shape, surface energy, and any potential contamination, play a crucial role. Also, environmental conditions are essential, including exposure to solvents or chemicals, temperature variations, and UV light. Finally, the application process—precisely the duration, temperature, and amount of pressure used—can significantly impact the adhesive’s performance. Understanding these factors is essential for optimizing your PSA application results.

How do you measure adhesion?

Adhesion is essential to how pressure-sensitive adhesives perform, reflecting the bond between the adhesive and the surface it sticks to. We often use the peel test to test the bond strength, which is recognized by standards like PSTC and ASTM. Peel values from this test provide insight into how effectively a PSA has bonded to a material.

There are two critical measures of adhesion to consider: initial adhesion and ultimate adhesion. Initial adhesion assesses how well a PSA bonds shortly after application, typically within seconds or minutes. In contrast, ultimate adhesion evaluates the bond strength after 72 hours. Both metrics are critical for understanding and optimizing the performance of PSA in various applications. By measuring these properties, we can ensure that products meet the highest standards of reliability and effectiveness.

How do you measure cohesion?

Cohesion refers to the internal strength of the pressure-sensitive adhesive film itself, which plays a crucial role in its overall performance. We use the shear test, which organizations like PSTC and ASTM standardize. The shear values obtained from this test provide valuable insights into the adhesive’s ability to maintain its bond under stress.

Adhesives with higher shear values indicate stronger cohesion, which enables them to withstand exposure to elevated temperatures and harsh chemicals. Understanding cohesion is essential for selecting the correct PSA for specific applications. By focusing on cohesion and adhesion, we can deliver products that meet our customers' demanding needs.