Thought Leadership
Answers to frequently
asked questions about
pressure-sensitive adhesives
There are many factors that brands and label converters need
to consider when choosing a pressure-sensitive adhesive
(PSA) for their product application, from cost to sustainability to
performance to design. With these considerations come plenty
of questions. For example, are some label adhesives more ecofriendly than others? Does the thickness of an adhesive matter?
Here are the answers to some of the most common questions
about PSAs.
How do pressure-sensitive adhesives work?
PSAs are adhesives that that will bond to a substrate surface
with little or no energy. Unlike solvents and hot melt adhesives,
which use chemical or mechanical processes to achieve
adhesion, firm pressure is all that’s needed to create a cohesive
bond between the PSA and substrate. This makes them ideal
for labels, tapes and graphic signage.
What are the different types of PSAs?
Adhesives fall into one of three families:
• Repositionable: An adhesive that adheres immediately,
but if a label is misapplied, it can be removed cleanly from
a container within a window of time, allowing a new label
to be applied.
Traits: Low adhesion
• Removable: An adhesive that can be easily removed
without damage to the label or substrate.
Traits: Low to moderate adhesion
• Permanent: An adhesive that is hard to remove and will
cause destruction of the label or substrate when removal
is attempted
Traits: High adhesion
Based on the product application, brand owners may need
an adhesive that falls into more than one category, such as a
removable, repositionable adhesive.
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Thought Leadership
Can one adhesive work with any application?
Unfortunately, no. There’s a reason there are more than 300
different PSAs in the adhesives industry. Specific applications
require label developers to create PSAs with specific performance properties, which can be achieved using several basic
components.
What components are used to make an adhesive?
All PSAs are built on either a rubber or acrylic base, combined
with a specific adhesive technology. There are four basic types
of adhesive technology: emulsions, solvents, hot melts and UVhot melts. By putting these components together in different
combinations, label developers can customize an adhesive to
deliver the right mix of durability, flexibility, thickness, adhesion
and other performance traits when the adhesive is applied to
a liner and facestock. Examples include a removable acrylic
emulsion PSA or a permanent rubber-based solvent PSA.
How do I choose an adhesive for my product
application?
Selecting the proper adhesive is essential to the success of
the label in each application. Understanding the environment
and use of the label will help label developers and converters
identify the correct adhesive for the application. Some factors
to consider include:
• Facestock: What type of facestock is being used?
• Adhesive: What type of adhesive is needed (permanent,
repositionable, etc.)?
• Substrate: What will the adhesive need to stick to?
• Application conditions: In what conditions will the label
be applied?
Why does the product container (substrate) affect which
adhesive can be used on it?
Adhesion strength of a PSA is dependent on several factors.
First is the surface energy, or the amount of molecular force in
the surface material it is applied to. High-surface-energy materials tend to be smooth and clean, and include metals, painted
surfaces, dry glass and certain plastics, such as HDPE, PET
and polypropylene. Waxy, soft and oily materials such as Teflon,
rubber and silicone have a low surface energy. Most PSAs
bond best when they can “wet out,” or spread on a surface.
But low-surface-energy materials reduce the adhesive’s wetout ability. So converters must use a more aggressive adhesive,
such as a solvent or hot melt, to bond to a low-surface-energy
substrate, whereas an emulsion, or water-based adhesive, will
work better with high-energy substrates.
Does the shape and texture of my container matter?
The shape and texture of a product container affects what PSA
properties are needed to achieve good adhesion. A container
that is bumpy or porous might require one set of adhesive
properties, just as a smoother, larger container may require
another set. In either case, adhesives can be adapted to maximize adhesion to the product’s surface area and texture.
Are PSAs environmentally friendly?
Although PSAs aren’t recyclable themselves, different adhesives offer different sustainable benefits for the end user.
For example, many emulsion PSAs enable labels to be easily
removed during recycling, which helps packaging reclaimers
yield more recycled material for remanufacturing. Solvents, on
the other hand, are harder to remove but require less energy
than a hot melt, and less water than an emulsion. UV-hot melts
and standard hot melts also eliminate the need for a label liner,
reducing liner waste. >
• Exposure conditions: In what conditions will the label
be used?
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All other brands and product names are trademarks of their respective owners.
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