PSAs are manufactured in a continuous process utilizing web technology, where the adhesive material is applied by a die head or highly polished roll to an unwinding roll of receiving material. The three major adhesive classifications are:

1. Solvent Based

   A solvent is used to dissolve the adhesive mixture. This liquid is used to coat an unwinding roll of material in a continuous web process. As the material moves through the process, heat and high velocity forced air are used to evaporate the solvent. The material is now coated with a dry, tacky adhesive. The adhesive, carrier and release liner are laminated together and rewound onto a roll. Depending on construction, the PSA may not have a carrier (transfer tape), or a release liner (self wound).

2. Hot Melt

   This is a solvent-free process that utilizes the flow characteristics inherent in heated elastomeric materials such as thermoplastic rubbers and tackifying resins. This heated compound is flowed onto an unwinding roll of material in a continuous web process. The adhesive is cooled prior to laminating and rewinding.

3. Emulsion

   This is a water based system where the adhesive ingredients are dispersed in water. This mixture is used to coat an unwinding roll in a continuous web process. As the material moves through the process, heat and high velocity forced air are used to evaporate the water. The material is now coated with a dry, tacky adhesive. The adhesive, carrier and release liner are laminated and rewound. As with the other two PSA manufacturing processes, depending on construction, the PSA tape may not have a carrier (transfer tape), or a release liner (self wound).

Each PSA has its own unique set of properties.

1. Rubber/Resin

   Rubber based adhesives generally offer higher adhesion and shear properties than acrylic or silicone adhesives. Based on natural or synthetic rubbers, these adhesives are mixtures that include ingredients such as tackifying resins and oils to improve wetting properties. They provide good to excellent initial tack and adhesion particularly in skin contact applications.

   Because of their strong bonding characteristics, many of the adhesives used in surgical applications are rubber based. They provide the strength and moisture resistance required in challenging environments.

2. Acrylic

   Acrylic monomer esters as a class, are polymerized to form polymer chains and are cross-linked to form high molecular weight polymers with the desired adhesive properties. Acrylic adhesives provide resistance to solvents.

   Acrylic adhesives offer many advantages in medical applications. Lower initial tack allows for repositioning for optimum effectiveness. All medical adhesive applications are temporary in nature, from an hour to days of adhesion, so a permanent bond is not required. Ease of removal is also an important consideration.

   In addition, acrylics are chemically inert so they typically cannot cause allergic reactions.

3. Modified Acrylic

   An acrylic adhesive is combined with tackifying resins to enhance bonding properties. They offer higher initial tack and improved bonding to low energy surfaces, but there is some loss of UV and solvent resistance.

   For medical applications, hydrocarbon tackifiers, which are chemically inert and hypoallergenic, have been developed.

4. Silicone

   Silicone adhesives are used for specialty applications such as high oxygen/gas permeability, low pain upon removal, and adhesion to and removal from sensitive skin.

The contour of the surface will influence both the adhesive selection and the product selection. For conformability around irregular angles and curves, materials with higher flexibility are recommended. Regardless of an adhesive’s strength, it is virtually impossible to overcome continued stress from a rigid material trying to return to its original form (memory).

• Consider a conformable tape with a flexible carrier such as a Non-Woven or urethane.

• Consider adding stress relief to a converted part (scores, perforations).

Each element of a PSA plays an important role. Avery Dennison Medical Pressure-Sensitive Adhesive tapes typically consist of three major elements:

1. Adhesive

   Sticky material, usually polymer based, that bonds one substance to another. Specific performance characteristics can be engineered into the formula.

2. Carrier

   The carrier supports and serves as a backing for the adhesive, providing reinforcing strength and dimensional stability, and contributes to the final properties of the product. Depending on the application, film, foam or Non-Woven materials are commonly used.

3. Release liner

   Usually coated with a cured siliconized release material for ease of separation, it is the material to which the adhesive is applied. The release liner is paired with a specific adhesive to promote ease of release and application.

NOTE: Transfer tapes (no carrier–adhesive with a release liner) are also available for specific applications.

It is important to understand the basic characteristics of each of these elements in selecting an adhesive tape construction for a specific application.

In the PSA manufacturing process the carrier is typically laminated to the adhesive coated release liner. The carrier can be thin (film) or thicker (foam) depending on the PSA and its application. The carrier supports the adhesive and helps determine the properties of the final product.

Film Carriers

A wide variety of thin plastic films are used as PSA carriers. Differentiating parameters include thickness, chemical resistance, barrier properties, tensile strength, elongation, temperature resistance and color. Typically, film carriers are all water resistant. Some examples are:

• Polyester (PET): This clear plastic film carrier can be used with most types of adhesives, offering high tensile strength and providing good barrier properties to most migratory chemicals.

• Polyethylene (PE): This flexible carrier material provides good chemical and solvent resistance.

• Polyurethane (PU): Polyurethane has no plasticizers to leach out and cause allergic reactions or hardening over time, retaining long-term flexibility and outstanding shelf life. Strong, flexible and waterproof PU is resistant to UV, chemicals, bacteria and fungus. Good water vapor transmission.

• Polypropylene (PP): This film is available in both oriented (clear) and non-oriented forms. The clear grades are typically used, although white or colored films are available.

• Polyvinyl chloride (PVC): This film is flexible and conformable with an exceptionally smooth finish.

Foam Carriers

Closed cell foam carriers are used to provide conformability to irregular surfaces and water resistance. Some examples are:

• Polyethylene (PE): Polyethylene foam is a durable, lightweight, resilient, closed-cell material available in a wide range of densities and colors. PE foam offers superb strength and tear resistance, flexibility, resistance to mildew, mold, rot, and bacteria, as well as to water, chemicals, solvents and grease.

• Polyvinyl chloride foam (PVC): This foam is flexible and conformable with an exceptionally smooth finish.

Non-Woven Carriers

Non-Woven carriers are engineered fabrics bonded together by entangling the fibers either mechanically, thermally or chemically. Non-Wovens are not processed into fabric by weaving or knitting, and the fibers are not made into yarn. Non-Woven carriers offer specific features such as absorbency, liquid repellence, resilience, stretch, softness, strength, cushioning, bacterial barrier and sterility. Some examples are:

• White EVA coated microporous Non-Woven

• White water repellent polyester Non-Woven

• Turquoise blue hydrophobic polyester Non-Woven

• White polyethylene Non-Woven

• Tan skin colored polyethylene Non-Woven

• White spun bonded polyester

• White release coated 100% viscose Non-Woven

• Compare CarriersPDF | 78 KB

A release liner is a protective covering for the adhesive to prevent “unwanted” adhesion and/or contamination of its surface during shipping and handling. Release liners are typically coated with a siliconised release agent to provide a desired release characteristic. Release is separation of the liner from the adhesive; the liner is the carrier for the release agent.

Release liners are constructed from various base materials, such as polyester and polypropylene films, and densified or polycoated kraft papers. Depending on the construction of the tape, release liners are coated on one or two sides with a release agent.

The liner is removed and discarded before application. These are the release materials used in Avery Dennison Medical pressure-sensitive adhesives.

• Kraft paper
• Super calendared glassine paper
• Clay coated paper
• Polyethylene protected paper
• Polyester film
• Polypropylene film
• Polyethylene film

Avery Dennison employs a wide variety of release coatings based on the adhesive and the release needs of the application.

• Compare Release LinersPDF | 78 KB

Single Coated

The adhesive is coated on one side of a carrier, which can be film, foam or Non-Woven. A release liner coated on one side with silicone protects the adhesive.

• Single coated films are used in wound care and surgical applications.

• Single coated foams are used primarily in electromedical and ostomy applications.

• Single coated Non-Wovens have application across a broad spectrum–from surgery to wound care.

• PU films are provided with and without added PE support (casting sheets).

Double Coated

The adhesive is coated on both sides of a film carrier material. This construction is provided on a liner coated on both sides with silicone. Double linered, double coated constructions may be offered.

• Offers improved internal strength.

• Greater dimensional stability, easier converting.

• Easily slit into narrow rolls.

• Adds support to otherwise stretchy materials.

Self Wound

The adhesive is coated on one side of a carrier. The other side of the carrier is generally coated with silicone to enable the tape to unwind easily. Self wound constructions are available with foam and Non-Woven carriers.

• Provides wraparound sealing.

• Acts as closure system.

• Self wound foam tapes are used in electromedical and ostomy applications.

• Self wound Non-Wovens are used in electromedical and wound care applications.

• Can provide moisture vapour barrier.

Transfer Tape

A film of unsupported adhesive is coated directly onto a siliconised release liner. The release liner is coated with silicone on both sides to ensure that the tape unwinds easily and can be laminated to various substrates. Double linered transfer tape constructions may be offered.

• Offers superior conformability.

• Ideal for device mounting and foam bonding.

• Acrylic transfer tapes are used in surgical applications.

• Hydrocolloid transfer tapes are used in ostomy and wound care applications.

Sheeted Products

Certain products are available in sheeted form.