Pressure sensitive adhesive tapes come coated with pressure sensitive adhesives, which makes it a self-sticking tape that adheres to substrates on coming in contact with the surface, aided by slight initial external pressure. These PSA tapes generally require no activation with heat, solvent or water and firmly adhere to majority of dissimilar materials.
The defining characteristics of PSA tapes are:
- Permanent tack
- Adhesion with low external pressure
- No liquid to solid phase
Advantages compared to traditional fasteners:
- Easy to use & quick bond formation
- Lightweight compared to other mechanical fasteners
- Fills gaps and creates a more aesthetically pleasing product.
- Reduces assembly time
- No advance technology required for the application
- Ease of removability without damage to the substrate.
Construction of PSA Tapes:
The PSA Tapes generally consists of two main components – carrier or backing material and adhesive and in certain cases it also consists of liner and reinforcement scrim/mesh.
Reinforcement: There are certain PSA tapes that come with glass/polyester yarn fibers scrim/mesh that is laminated on the carrier, in order to improve the strength of the product. e.g.: Cross Filament, Alu-Glass, RGPT etc.
Carrier
The suitable carrier such as paper, foil, fabric or film is selected depending on the application, tensile strength, elongation, tear resistance, environmental factors etc. required. The adhesive is coated after initial surface treatment such as primer, corona, release-coating or water-proofing on the carrier depending on the requirements of the carrier. The adhesive coating is also done by using different methods such as coma coating, mayer-bar coating etc. depending on factors such as coating weight, backing/ carrier material etc.
*Primer & corona treatment: It increases the holding power of the adhesive to the backing material.
*Release coating: To allow for the winding and unwinding of the tape, the backing is coated with a release agent that somewhat prevents the tape from sticking to itself or the sticking of two adhesive layers (double-sided tapes).
*Water-proofing: The water-proofing is generally done on the top side (opposite side of the coating) of the various cloth carriers to make the PSA tapes resistant to water.
Adhesive
- Rubber: Rubber adhesive is made from natural/synthetic rubber by adding hydrocarbons, tackifiers, antioxidants, accelerators, curing agents during mastication process as per the adhesive formula. The PSA Tapes with rubber adhesive is mainly used in applications where temperature resistance is required along with masking properties such as masking tapes, duct tapes, polyester tapes for insulations etc.
- Acrylic: Acrylic adhesives are tacky & flexible, with good resistance to wear and tear by solvents and external environmental factors. There are 2 types of acrylic adhesive:
Solvent acrylic is a resin-based adhesive comprising of acrylic or methylacrylic polymers dissolved in a solvent and offers good cohesion and adhesion. Hence it is a popular choice for a wide-range of PSA tapes, even though the adhesive does not adhere well to low surface energy substrates such as plastics but has better adhesion than rubber adhesive.
Emulsion acrylic is a mixture of water, polymers and additives, and is a very cost-effective as well as environment friendly option in comparison to solvent acrylic adhesives. The adhesive is ideal for paper tapes used in packaging or surface protection tapes. The water-based property of the adhesive makes it prone to moisture, this it’s not as preferred as solvent acrylics.
- Silicone: Silicone adhesives are the costliest of all the adhesives used in PSA tapes and is made from polymer that mostly consists of siloxane bond mixed with various compounds. The silicone PSA adhesive can tolerate very high or low temperatures and also handles extreme environments better than other adhesives. The approximate operating temperature of the silicone adhesive ranges from -100° F (-75° C) up to 390° F (200° C) and in some cases up to 575° F (300° C) for short periods. Silicone adhesive is also nearly inert to chemicals and has excellent resistance to moisture and weathering.
- Hotmelt: They are 100% solid thermoplastic resins that liquefy when heated and hardens on cooling on the substrate after coating, reaching their bond strength within seconds. The adhesive can be applied through various methods such as extrusion, rolling or spraying. The variety of polymers in this class is very wide and includes both natural and synthetic polymers and as it is thermoplastic polymers, it can be repeatedly heated to melt and cooled to solidify. Hotmelt adhesive tapes are mainly used in the printing, automotive, textile industries.
What are the Different Types of PSA Tapes:
There are different kinds of PSA tapes such as Single Side, Double Side, Transfer Tape, Reinforced Tape etc.
Single Side PSA Tape: Adhesive coating is done only on one side of the carrier and may come with or without a liner.
Double Side PSA Tape: Adhesive coating is done on both sides of the carrier and always comes with a liner.
Transfer PSA Tape: Adhesive layer itself acts as a carrier. It always comes with the liner.
Reinforced PSA Tape: Reinforcement scrim/mesh as explained above is laminated on to the carrier and after coating of the adhesive, it gives extra strength to the PSA Tape.
What is the Production Process of PSA Tapes?
The required carrier or backing material is coated with cohesive adhesive. The correct combination of carrier and adhesive depending on the various quality factors required is very essential for manufacturing good quality PSA tapes. The non-release side of the carrier (after passing it through surface treatments such as priming, release-coating, corona-treatment, and waterproofing etc. if required) is coated with adhesive using different coating methods such as coma-coating, mayer-bar coating, etc. depending on the coating weight, carrier type.
The carrier along with the coated adhesive is then passed through an oven chamber in which the required temperature is set, depending on the type of adhesive and carrier being used, that is required to cure the adhesive. The PSA tape after passing through the heated chamber is winded on to a jumbo roll which is then stored in a curing room for a minimum of 7 days.
On completion of 7 days of curing, the jumbo roll is then transferred to the rewinding and logging station, during which the jumbo roll undergoes quality check such as any occurrence of adhesive transfer, uneven coating, whether the carrier has developed wrinkles or has been unevenly stretched.
The final process is transferring the good quality jumbos either to warehouse for processing of future orders or to the conversion station where the jumbo roll is converted into log rolls or cut-size rolls depending on the customer specifics.
What are the Parameters for Checking/Testing PSA Tapes?
- Thickness of the carrier:
Micron: It shows that thickness of the carrier and is mostly used in plastic film based carriers such as polyester, LDPE.
GSM: It stands for grams/1 square-meter and it indicates the weight of the carrier in grams for one square-meter area. This is mostly used in paper or cloth based carriers.
- Peel Adhesion: This test parameter measures the approximate force required to peel off the PSA tape from a substrate or its own backing material. It is also commonly known as adhesion to steel as during the test, the PSA tape is applied on a steel plate.
- Roll Ball Tack: This test measures the initial stickiness of the adhesive on the PSA tape at the time of application on the intended substrate.
- Shear adhesion
The time required for a tape to come loose at a particular attached weight from a vertical panel decides the shear strength of the PSA tape. Internal or cohesive strength of adhesive coated is tested.
- Temperature test
Shows the range of operating temperature that a particular PSA tape will withstand determining its temperature resistance and how it will behave in different climate conditions.
- Breakdown voltage
It is the maximum voltage stress which a single layer of PSA tape can withstand before dielectric failure occurs. This test basically determines the electric strength of insulating tapes.
- Tensile strength
It is a test determining the force that is required to break the PSA tape.
- Elongation
It tells how far the PSA tape can stretch before it breaks. Elongation test indicates as how well the tape can handle the continuous stress of being stretched, once it is applied / at the time of application.
How to choose a right PSA tapes?
- Understanding the exact application
- Determine the surface of the substrate on which the tape will be applied.
- Check whether it is for interior or exterior (outdoor) use/application & and if any specific temperature resistance is required.
- The intended duration required after the application of the PSA tape.
- Type of bond (permanent or temporary).
