Pressure sensitive adhesives (PSAs), also known as self-adhesives, represent a category of adhesive media characterized by specific properties that make them capable of bonding surfaces by the application of simple pressure without requiring heat, solvents or chemical activators.
They are distinguished from other types of adhesives by their excellent adhesion ability, great hold and versatility of use. Let’s take a closer look at how they are made and which types might be best suited for your applications.
How PSAs are made
Chemically, PSA adhesives are formulated with a system of special polymers, known as acrylic or synthetic rubber polymers, together with selected resins and plasticizers to achieve a sticky consistency at room temperature. These polymers form a three-dimensional network structure within the adhesive, which provides both bond strength (the ability of the adhesive to adhere to a surface when pressure is applied to it) and cohesion (the ability to maintain internal integrity and strength).
How pressure sensitive technology works
The key to the functionality of Pressure Sensitive Adhesives is in the very balance between adhesion strength and cohesion. That is, they are formulated to have a greater adhesion strength than cohesion, which means that they tend to adhere to a surface to a greater extent than their constituent particles hold together. This balance allows them to bond effectively with light pressure.
Adhesion therefore takes place immediately, as soon as sufficient pressure is applied to the adhesive film. This type of adhesive is already cured, and bonding happens by taking advantage of the electrostatic interactions present on the target surface.
This is the most obvious difference from other types of adhesives that, unlike PSAs, require processes such as solvent evaporation, water absorption, reaction to UV radiation, a chemical reaction, or cooling after hot application.
In fact, while adhesives that have a liquid part need to wait for the glue inside them to harden, pressure-sensitive ones are sufficiently sensitive to bond permanently after a simple pressure, while still being extremely strong and durable.
Types of PSAs
There are different kinds of pressure sensitive adhesives that differentiate in terms of the material from which they are formulated. Each type of PSA adhesive has its own specific properties, and the choice will depend on the needs of the application. It is important to select the right PSA adhesive based on the materials to be bonded, the environment in which it will be used, and the desired duration of adhesion. Here are the main types:
Acrylic adhesives are the most widely used industrial adhesives because they can be used on a very wide range of surfaces due to their chemical composition and also because they resist deterioration given by time, environmental conditions, high temperatures, vibration and dynamic stresses very well, as well as being fire retardant.
Silicone adhesives are also able to withstand very high and very low temperatures, as well as the mold and mildew that can be created due to prolonged application. They can also bond well to silicone materials.
Synthetic rubber base adhesives, which are cheaper, depending on the type of rubber used, may experience aging due to prolonged exposure to sunlight (UV rays), but they enjoy high adhesion with very fast initial bonding and are well suited to many surfaces.
Then there is also the category of pressure sensitive removable adhesives designed to be removed without leaving residue or damaging the surfaces to which they are applied. They are commonly used for the production of removable labels, stickers, and for classic post-it notes.
Thermoplastic pressure-sensitive
A special type of pressure sensitive are Hot Melt, which are composed of polymers, with no solvents in them, that can adapt to applications on difficult surfaces such as plasticized or painted surfaces. Hot Melts work so well because they have a specific formulation that compensates for the unevenness of the surfaces to which they are to be bonded, and they enjoy great strength.
The Industrial Adhesives division of the Diatec Group specializes in the production of this type of adhesive, with excellent results thanks to its experience and continuous research into innovative, technological and effective solutions. Contact us to receive more technical information about pressure sensitive adhesives and their use: our consultants will be able to answer all your questions.