Common Chemistry of Pressure Sensitive Adhesives and Tapes

According to the Pressure Sensitive Tape Council, three characteristics define a Pressure Sensitive Adhesive (PSA):

1. Permanent tack
2. Adhesion with light pressure
3. No liquid-to-solid phase change

Unlike liquid adhesives, the chemistry in a tape is provided fully cured so there is no additional curing that takes place to form a bond. The bond is created by using mechanical interlocking and electrostatic interactions at the interface.

These characteristics give PSAs unique performance capabilities that can provide freedom when designing a product and increase production efficiency. Benefits may include:

Instant handling strength after applying pressure
Easy to apply
Consistent bond thickness
Various thickness options with and without carriers and functional foam cores
Precise application with preformed (converted) shapes
Preassembly possibilities throughout the value chain
Bonds dissimilar materials without damaging surfaces
Metal-to-metal barrier for reduced galvanic corrosion

Pressure sensitive adhesives come in many different formats including double coated tapes in various thicknesses with carriers or functional foam cores, adhesive transfer tapes, single coated tapes, and printable films. In addition to formats, there are a wide variety of chemistries used in PSAs for industrial bonding applications. Although specialty PSAs can be found in many applications, we will focus on providing a high-level overview of the three most common chemistries for comparison purposes. There are many other factors to consider when choosing the proper tape or adhesive for use in an assembly.

Acrylic
Silicone
Rubber

Acrylic Adhesive Tape

Development of acrylics for pressure sensitive adhesives began because of the tendency of natural rubber to yellow and degrade when exposed to UV. Acrylic chemistry also tends to have higher internal strength than rubber chemistry.

Acrylic tapes are the workhorse of industrial bonding. The ever-evolving capabilities of acrylic chemistry allow formulations to provide high or low temperature performance, adhesion to High, Medium, and Low Surface Energy (HSE, MSE, LSE) materials, or even unique properties such as flame retardancy. Acrylic tapes are provided in various thicknesses with and without carriers and functional foam cores. Functional foam cores of acrylic foam tapes offer specific performance benefits including strength and dynamic stress absorption. Acrylic tapes are found in nearly every industry.

Primary Advantages

Ability to bond to the widest range of materials

Widest variety of mechanical performance capability

Good resistance to aging and environmental conditions

Functional acrylic foam cores available for dynamic stress and vibration absorption

Primary Disadvantages

Not as high temperature resistance as silicone, although very high temperature acrylics are available

Longer time to full strength than rubber, although handling strength is typically immediate after pressure and final strength is typically higher

Silicone Adhesive Tape

Silicone-containing polymers can be used to create tape release liners due to their incredibly low surface energy but are also used to formulate the very adhesive itself.

Silicone tapes are best known for their ability to bond to silicone and to tolerate a very wide range of temperatures – from -40 °F (-40 °C) to over 500 °F (260 °C).

Primary Advantages

Ability to bond to silicone materials

High temperature resistance

Relatively resistant to mold and fungi

Primary Disadvantages

Relatively low strength

Low bond strength on non-silicone materials, although double coated tapes are available with silicone on one side and acrylic on the other to allow bonding silicone to non-silicone

Because silicone is “inorganic”, meaning that the backbone of the chemistry is non-carbon, it is inherently hypoallergenic and relatively resistant to molds and fungi.

Rubber Adhesive Tape

Rubber was the first material used to make pressure sensitive adhesives. Over the decades, rubber PSA technology has advanced to include both natural and synthetic rubber resins and a wide variety of tackifiers used to tune the adhesive for specific performance.

Rubber adhesives build the bond faster than other chemistries, they can bond to most surfaces including LSE and are relatively lost cost. They are a versatile option for many applications, however their final bond strength is lower than acrylic PSAs and they are more vulnerable to the effects of aging (sunlight and oxidation).

Primary Advantages

Fast initial bond (high tack)

Adhesion to low surface energy substrates

Relatively low-cost solutions

Primary Disadvantages

Lower ultimate strength compared to acrylic PSAs

Lower resistance to environmental conditions (e.g. UV, temperature)

Natural rubber (poly cis-isoprene) is mechanically worked to provide lower molecular weight polymers that can be readily dissolved or dispersed in a solvent. Synthetic polymers (such as styrene-isoprene block copolymers) may also be used. Tackifiers such as pinene (from pine sap, among other sources) are added to give the adhesive additional tackiness allowing it to be used as a PSA.

As with other adhesives, the chemistries and construction for tapes grow every day. New adhesives, new carriers and new manufacturing processes mean that new industrial tapes will continue to be developed.

The Science of Adhesion Educational Series

The Science of Adhesion Educational Series is designed to be a comprehensive introduction to Adhesion Science and the use of tapes and adhesives in design applications. Visit the Science of Adhesion page to view all articles or choose from the selected topics below.

Common Chemistry of Pressure Sensitive Adhesives and Tapes

Acrylic Adhesive Tape

Silicone Adhesive Tape

Rubber Adhesive Tape

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