Understanding Pressure Sensitive Adhesives and How They’re Made
Pressure-sensitive adhesives, also known as PSAs are used in the manufacturing of many products, as well as hundreds of other products. Their applications span across every industry, making them a crucial part of today’s infrastructure. This is your guide to pressure-sensitive adhesives, what they are, and how they are made.
What are Pressure-Sensitive Adhesives?
A Pressure-sensitive adhesive (PSA) binds two surfaces together when pressure is applied without requiring a solvent, water, or heat activation. The strength of the bond is determined by the amount of pressure applied during installation.
How Do PSAs Work?
PSAs work by placing the adhesive between the two products that you want to be bonded together. It is crucial to apply adequate pressure during installation. Otherwise, the attachment between the two substrates will be weak and break, or there may be defects such as bubbles. Pressure-sensitive adhesives are not classified as actual solids. This means as the temperature increases, the strength of the bond decreases. However, at room temperature, this type of adhesive is strong and permanently sticky.
Uses of Pressure-Sensitive Adhesives
Pressure-sensitive adhesives can be used for either temporary or permanent applications across almost every industry. You can bond materials such as plastic, paper, metal, glass, and wood. Examples of specific uses include labeling food packaging, assembling electronic devices, mounting graphic displays, and much more.
Types of Pressure-Sensitive Adhesives
There are four main types of PSAs. The type you choose to use will depend on the application.
1. Adhesive Tape
Adhesive tape winds onto itself without a liner and is the most common type of PSA used in daily life. Examples include:
- Masking tape
- Duct tape
- Cellophane tape
- Electrician’s tape
2. Single-Faced Product
This type of PSA consists of a non-adhesive side such as paper or picture and an adhesive side with a liner that can be easily removed when it is time for installation.
3. Double-Faced Product
A double-faced pressure-sensitive adhesive is similar to a single-faced PSA, except that both sides have an adhesive with a carrier membrane in the middle. The most common example is double-sided tape.
4. Transfer Tape
Transfer tape is wrapped around a release liner. It has adhesive on both sides but does not have a carrier membrane in the middle. This PSA’s characteristics make it highly versatile and capable of meeting any thickness requirement. Application examples include:
- Manufacturing of electronics
- Manufacturing of vehicles
What Materials are PSAs Made Of?
PSAs made out of rubber/resin are a combination of rubber (natural or synthetic) and resins such as oils and antioxidants, depending on the formulation. These are either made via the solvent-based or hot melt method. Rubber adhesives make for powerful bonds across a variety of materials. They possess high tack qualities. Their most significant disadvantage is that exposure to chemicals can decrease the strength of the bond. Rubber PSAs are ideal as general-purpose adhesives and are economical. They are your most common pressure-sensitive adhesives.
Acrylic is the second most popular type of PSA. Resins, monomers, and other chemicals can be added to change the adhesion properties. Even though acrylic PSAs are durable, they do not have as much strength as those made of rubber. The main advantage is that they are UV resistant and not as susceptible to oxidation. Other benefits include the capability of bonding well to a variety of surfaces, including metal, glass, and polycarbonate. They have high tack as well. However, they do not adhere well to polyethylene and polypropylene surfaces. These properties make acrylic PSAs the optimal choice for many outdoor applications.
Silicone pressure-sensitive adhesives are the least common of three, but they still have their place. They are comprised of silicone polymers that can maintain strong bonds of a wide range of temperatures compared to rubber and acrylic PSAs. As compared to adhesives made of rubber and acrylic, adhesion strength is relatively low, while the cost of silicone PSAs is higher than the other two.
How are PSAs Made?
Pressure-sensitive adhesives can be made via four different methods. Here’s what you need to know.
This method involves dissolving the ingredients in a solvent. The mixture is then applied to the substrate. Once this occurs, the solvent is force evaporated, leaving behind the pure adhesive that can then be packaged.
Instead of being dissolved in a solvent, the ingredients are dispersed in water. They are then applied to the substrate, just as in the solvent method. Force evaporation occurs to remove the water leaving just the adhesive, which can then be packaged. It is of interest to note that adhesives made via the water-based method are lower in cost yet perform just as well as solvent-produced adhesives. They are more cost-effective because not as much labor is required to make them.
The hot-melt method is different from the water-base and solvent methods. This process involves mixing the ingredients together and heating the mixture until it flows. It is then applied to a substrate, cooled, and ready for packaging. Hot-melt provides the best of both worlds because it is cheaper than solvent-based adhesives and works well with most substrates due to its high coatability.
This method uses UV light to cure the adhesives. In fact, in most cases, you don’t even have to mix the ingredients together. They are an attractive option because UV-curable adhesives do not contain solvents or volatile components, making them environmentally friendly. In addition, they cure quickly at relatively low temperatures, making them the perfect adhesive choice for heat-sensitive substrates.
One-Stop-Shop for Pressure-Sensitive Adhesives
Lamart Corporation is the leader in PSAs. No matter what industry you are in, from graphic arts to aerospace, we’ve got the adhesive you need to get the job done. Shop our full line of pressure-sensitive adhesives today!