Our Blog

PSAs Explained: What is a Pressure Sensitive Adhesive?

Pressure-sensitive adhesives (PSAs) are pivotal in modern-day adhesion technology, offering convenience and versatility across many applications. From the ever-present sticky notes on our desks to the intricate medical tapes that meet stringent healthcare requirements, a pressure sensitive adhesive can provide bonding solutions that ensure lightweight materials hold fast under varying pressures and with minimal effort.

This article delves into the science behind PSAs, exploring the different types, benefits, and when to use them. We will also discuss where to buy them and answer other frequently asked questions.

How a Pressure-Sensitive Adhesive Works

Pressure-sensitive adhesive tapes are remarkably straightforward. They remain tacky at room temperature and effortlessly adhere to surfaces upon applying light pressure. When pressure is applied, the adhesive flows to cover the surface area it is in contact with, causing sufficient tack.

PSAs offer a perfect balance between flow and resistance to flow, a property known as viscoelasticity. This property lets them wet the surface upon contact, ensuring a solid and immediate bond. They are elastic enough to be removed cleanly from the bonding surface, yet they have enough strength to resist flow when stress is applied.

The PSA formula can include elastomers, resins, plasticizers, and other additives, which can be adjusted to impart specific characteristics suitable for various applications and substrates.

Advantages of Pressure Sensitive Adhesives

Pressure-sensitive adhesives offer many advantages that make them popular for various applications across different industries. Here are some key benefits:

  • Ease of application and clean removal
  • Immediate bond
  • Versatility
  • Low prep cost
  • Flexibility and conformability
  • Safety and cleanliness
  • Sealing properties

When to Use Pressure Sensitive Adhesives

Pressure-sensitive adhesives (PSAs) are ideal for applications requiring quick and easy bonds without heat, solvents, or water activation. They are particularly suited for use in labels and stickers, medical tapes, graphic films, and assembly of lightweight materials.

PSAs offer the advantage of immediate bonding to a variety of surfaces, including plastics, metals, and paper, making them versatile for both industrial and consumer applications. Their ease of use, combined with strong and durable adhesion, makes them a preferred choice for situations where a fast, reliable bond is necessary.

4 Types of Pressure Sensitive Adhesives (PSA)

There are four primary categories of pressure-sensitive adhesives:

rubber pressure sensitive adhesives

1. Natural Rubber PSAs

Companies use natural rubber-based adhesives because of their strong tack, high peel strength, and relatively low cost. We often get asked about silicone vs rubber PSAs, here are the specifics so you can compare: 

  • Tack: Natural rubber PSAs typically offer high pressure-sensitive tack due to their inherent stickiness and the ability to quickly wet out the surface when applied.
  • Bond Time: Although they bond instantaneously under pressure, they also mature over time, increasing adhesion strength within the first 24 hours after application.
  • Indoor vs. Outdoor: Natural rubber adhesives are more suitable for indoor applications because they are prone to oxidation and can degrade under UV light and extreme weather conditions.
  • Food Exposure: Certain grades of natural rubber adhesives are FDA-approved for indirect food contact.
  • General Cost Info: Natural rubber PSAs are generally considered cost-effective compared to synthetic rubber or acrylic PSAs.
  • Temperature Range: PSAs are best suited for temperatures between 0°F and 180°F. When exposed to very low temperatures, the adhesive can stiffen and lose tackiness, which impacts application. High temperatures result in the adhesive becoming softer and more fluid, which decreases bond strength. 
  • Specific Uses:
    • Packaging: Used in tape for carton sealing due to its instant tack and strong bond.
    • Graphic Arts: Suitable for mounting lightweight displays and promotional materials.
    • Medical: Employed in surgical tapes and bandages for their strong adhesion to skin and conformability.
    • General Assembly: PSAs are used in various industries for temporary fixing or permanent attachment where high initial bond strength is required.

It is important to remember that natural rubber PSAs might not be compatible with certain plastics, such as polystyrene or polyethylene, because plasticizer migration could weaken the bond.

synthetic rubber pressure sensitive adhesives

2. Synthetic Rubber PSAs

Synthetic rubber pressure-sensitive adhesives have specific advantages and characteristics and are also used in many applications. Let’s explore the particular uses and properties of synthetic rubber PSAs:

  • Tack: Synthetic rubber PSAs generally offer good to excellent initial tack, with the ability to create a strong bond quickly after application on various substrates.
  • Bond Time: Similar to natural rubber adhesives, synthetic rubber PSAs form a strong bond quickly under pressure and may continue to strengthen over time.
  • Indoor vs. Outdoor: Many synthetic rubber PSAs are designed with added resistance to weather, UV light, and ozone, which makes some suitable for outdoor applications. 
  • Food Exposure: Some synthetic rubber adhesives may be suitable for indirect food contact applications if they meet the necessary FDA regulations. 
  • General Cost Info: The cost of synthetic rubber PSAs can vary based on the polymer type, resins, and any other additives. They are typically more expensive than natural rubber adhesives but less expensive than pure acrylic adhesives.
  • Temperature Range: Synthetic rubber adhesives typically perform well within a range of approximately -40°C to 80°C (-40°F to 176°F). They are generally more resistant to elevated temperatures than natural rubber PSAs.
  • Specific Uses:
    • Construction: It is used in waterproofing, vapor barriers, and roofing materials because it is weather-resistant and has strong adhesion to different materials.
    • Medical: It is utilized for skin contact, such as in sports tapes and wound care, due to its hypoallergenic properties and conformability.
    • Labeling: Used for making labels and tapes that might be exposed to challenging conditions, including humidity, light chemical exposure, or changing temperatures.

As with any adhesive, it’s imperative to test the compatibility of synthetic rubber PSAs with the specific substrates and conditions of the intended application.

acrylic pressure sensitive adhesives

3. Acrylic PSAs

Acrylic pressure-sensitive adhesives offer a unique set of properties that suit a variety of applications. Below is a breakdown of their characteristics and specific uses:

  • Tack: Acrylic PSAs usually have lower initial tack than rubber-based adhesives. However, the right formulation can adjust tack levels to meet diverse application needs.
  • Bond Time: They often have a longer bonding time, meaning the adhesive reaches its maximum strength after a certain period (usually 24-72 hours), known as the “dwell” time.
  • Indoor vs. Outdoor: An acrylic PSA typically exhibits excellent UV resistance and weatherability, making it ideal for indoor and outdoor applications. 
  • Food Exposure: Specific formulations of acrylic adhesives comply with FDA regulations, making them suitable for indirect food contact applications. 
  • General Cost Info: Acrylic PSAs are generally more expensive than rubber-based adhesives.
  • Temperature Range: Acrylic adhesives have an excellent temperature range, typically from about -40°F to 250°F. 
  • Specific Uses:
    • Automotive: They are utilized for trims, emblems, and sound-dampening films, given their resistance to temperature fluctuations and outdoor conditions.
    • Signage/Graphics: Ideal for outdoor signs and decals due to their UV resistance and long-term durability.
    • Electronics: Used in bonding and insulation devices, they can withstand elevated temperatures and not degrade quickly.

Acrylic polymers, made from acrylic acid or acrylate derivatives, can be engineered to have specific properties by adjusting their composition, molecular weight, and the addition of other substances during polymerization. For example, co-polymers created with other acrylic monomers can enhance the flexibility, impact resistance, or adhesive properties of the resultant material.

silicone pressure sensitive adhesives

4. Silicone PSAs

Silicone pressure-sensitive adhesives possess particular attributes that set them apart from other adhesive families. Here is a breakdown of their use and characteristics:

  • Tack: Silicone PSAs have a relatively low initial tack compared to rubber or acrylic adhesives. However, they adhere well to various surfaces, including low-surface energy substrates like silicone rubber and fluoropolymers.
  • Bond Time: Silicone PSAs typically require a longer bond time to achieve full adhesion strength, which may take up to 24 hours or more.
  • Indoor vs Outdoor: These adhesives are well-suited for indoor and outdoor applications. They have excellent resistance to UV light, ozone, and weathering, which makes them highly durable in exterior settings.
  • Food Exposure: Certain silicone adhesives comply with FDA regulations for indirect food contact and can be used in applications such as food processing, kitchenware labeling, and appliances. 
  • General Cost Info: Silicone PSAs are generally more expensive than other types of adhesives because of their temperature stability and chemical resistance.
  • Temperature Range: One of the most significant advantages of silicone PSAs is their extreme temperature range, typically from about -67°F to 392°F.
    Specific Uses for Silicone PSAs
    • Aerospace: They withstand dramatic temperature changes and maintain adhesive performance.
    • Automotive: Applied in engine-parts bonding, heat-resistant labels, and gaskets for high-temperature environments.
    • Industrial: Because of their temperature and chemical resistance, they are utilized for splicing tapes in high-temperature processes and masking during powder coating.

Where to Buy Pressure Sensitive Adhesives

Rubber Resource stocks several PSAs and has access to many more through our partnerships with 3M, Scapa, Adchem, and others. If we don’t have what you need in our inventory, we know where to find it as quickly and economically as possible. Reach out to us here for all your PSA needs.

Frequently Asked Questions About Pressure Sensitive Adhesives (PSAs)

What are the disadvantages of a pressure sensitive adhesive?

Some PSAs have disadvantages that affect their suitability for specific applications, such as temperature sensitivity, environmental resistance, leaving a residue, cost, strength degradation, yellowing, and lower load capacity. 

How long does a pressure sensitive adhesive take to cure?

The curing time for PSAs can vary depending on several factors, including the specific formulation of the adhesive, the materials involved, the environment, and the application pressure. Most PSAs provide an instant bond and achieve their full bond in several to 72 hours.

What is an acrylic pressure sensitive adhesive?

Acrylic pressure-sensitive adhesives come from an acrylic polymer base that provides adhesive properties. They can be formulated to offer a range of characteristics, such as differing levels of tackiness, resistance to environmental conditions, and longevity.

How does silicone vs rubber PSA compare?

Natural rubber PSAs provide high initial tack and strong bonding capabilities suitable for indoor applications, while silicone PSAs offer lower initial tack but excel in outdoor environments with excellent UV resistance and temperature stability. Natural rubber adhesives are cost-effective and ideal for applications requiring immediate bonding, whereas silicone adhesives are pricier but offer superior performance in extreme conditions, making them suitable for aerospace, automotive, and industrial applications. Ultimately, the choice between them depends on specific application needs regarding tack, bond time, environmental factors, temperature range, and budget constraints.

Leave a Comment