Double sided and trasfer tapes are used in a wide variety of applications in many industries. They often plan an important tole in securing workpieces to ensure effecient and safe seals and bonding. Double coated or double sided tapes are coated with adhesive on both sides of the backing or carrier. Transfer tapes consist of a thin adhesive film without a carrier or backing. Double coated and transfer tapes are used between or within the joint between two surfaces. They can also be used to assemble, mount or bond two or more components together. These tape products often replace liquid resin adhesives, hot melt adhesives, fasteners, solders, braze or welding depending on the specific part, join configuration and bond strength requirements.

Tapes in general are made by combining an adhesive material to a backing or carrier. 

Double-sided tape is coated with adhesive on both sides and allows the joining of items back-to-back.

Transfer tape consists of a single layer of adhesive without any backing. The internal strength of the tape holds the adhesive together. It is used in applications which require flexibility and stretch. Transfer tape can also join parts between mating surfaces in a back-to-back or butt joint fashion and pieces with irregular surfaces.

Adhesion Type

Adhesive tapes work differently depending on adhesive coating, adhesive cure technology and backing. The backing or carrier can also result in performance differences due to strength or thermal characteristics. For more information on adhesive material please read the Adhesive Tape Specification Guide.

Air setting or film drying materials form a bond or "harden" by evaporating water or an organic solvent. Many pastes and gum adhesives are film-drying.

Anaerobic adhesives cure in the absencfe of air or oxygen.

Thermoplastic or hot melt adhesives can be repeatedly softened by heat and then hardened or set by cooling, which allows parts to be removed or repositioned during assembly.

Thermoset adhesives are crosslinked polymeric resins cured using heat or heat and pressure. Cured thermoset resins do not melt and flow when heated, but they may soften.

Room temperature curing or vulcanizing products are polymer resins or compounds that either cure or vulcanize at room temperature. Vulcanization is a thermosetting reaction involving the use of heat and/or pressure in conjunction with a vulcanizing agent.

Pressure sensitive adhesives (PSA) adhere to most surfaces with very slight pressure and retain their tackiness. They form viscoelastic bonds that are aggressively and permanently tacky, and adhere without the need of more than finger or hand pressure.

UV or radiation cured adhesives use ultraviolet light, visible light or electron beam (EB) irradiation to initiate curing which forms a permanent bond without heating or excessive heat generation.

Reactive/moisture cured resins are single-component adhesives that are applied in the same way as hot-melt adhesives.

Single component adhesives or sealant systems consist of one resin that hardens by reaction with surface moisture, a surface applied activator-primer or through the application of heat.

Two or multi-component adhesive or sealant systems consist of two or more resins or a resin and a hardener, crosslinker, activator or catalyst that when combined, react and cure into a polymerized compound or bond. Two component systems are mixed and then applied.

Adhesive Properties

Adhesion is the ability to stick or bond to a substrate. In order to select the appropriate adhesive for the application, there are additional factors which should be considered. Double sided and transfer tapes differ in terms of physical properties and thermal properties, as well as dimensional specifications such as length, height and width. The performance properties for foam bonding tapes include peel strength or adhesion, tensile or break strength, and temperature resistance.

Type of Adhesive Materials

There are several types of adhesives available. They each have advantages and disadvantages depending on the desired application.

Acrylic adhesives create a permanent bond. They are available as a two part adhesive, which means they are made by mixing two or more components that react chemically to form a chemically cross linked adhesive. Acrylic can also be purchased in a form that is cured by exposure to UV light. They provide excellent environmental resistance and faster setting time than other resin systems. Acrylic adhesives tend to have a high cohesive strength; this allows them to withstand many different solvents. This type of adhesive cannot be used at temperatures above 300°F.

Hot melt, also known as heat activated, become tacky or sticky when heat is applied. They are a blend of polymers, with a high percentage of ethylene vinyl acetate. The adhesive may soften, but not necessarily melt and is applied as a liquid or high viscosity paste. Hot melt adhesives are available as fast set, delayed set, and pressure sensitive types. The types of adhesive can be repeatably softened and melted by heat, and hardened or set by cooling. They are available at various tackiness levels.

Pressure sensitive adhesives (PSA) are permanently tacky at room temperature in dry, solvent free, form. They adhere firmly with light pressure to a variety of dissimilar surfaces upon contact. PSAs do not require water, solvent, or heat activation in order to exert a strong adhesive force on materials such as paper, plastic, wood, and metal. PSAs have a sufficiently cohesive hold and elastic nature so that despite their aggressive tackiness, they can be manipulated by and removed from smooth surfaces without leaving a residue.

Rubber-based adhesives provide highly flexible bonds and are usually based on butadiene-styrene, butyl, or nitrile compounds. Rubber adhesives are inexpensive and provide high initial strength. They are adequate for short term, non-critical applications, such as indoors. Rubber has a very limited chemical, temperature, and UV light resistance.

Silicone adhesives and sealants have a high degree of flexibility and very high temperature resistance. The adhesives have an inorganic backbone and organic side groups that are especially formulated for premium performance. They form bonds with silicone-coated and other LSE surfaces, and are able to remove cleanly from some substrates.

Backing or Carrier Material

Double sided and transfer tapes and films vary in terms of carrier material. The carrier or backing material for double sided or transfer tapes is a relatively thin, flexible material to which the adhesive is applied. It functions to stabilize the adhesive, improve handling, and provide removability. The carrier also adds thickness to the tape and provides a barrier between adhesive layers. Films are synthetic resin adhesives that sometimes include a carrier fabric.

Transfer tape consists of a thin adhesive film without a carrier. The tape can be transferred to most dry surfaces from a peel-away release liner. Transfer tape and double coated tapes often use a release liner to enable or improve handling and dispensing of the tape product. Liners for double-sided tapes often incorporate differentially coated release liners that are easy to peel. These release liners are made of paper, film or silicone sheets. Board liners are heavyweight paper liners. Other backing materials include cloth, foam, paper, plastic, rubber, silicone and urethane.

Release or liner materials for double sided tapes and transfer tapes may be differentially-coated for easier peeling.Applying a different release coating on each liner varies the degree of release and allows one liner to peel away from the tape easily. Some release liners are made of paper, film, or silicone-treated sheets. Others are coated with clay or wax. Glassine is a transparent, high-strength liner material that is produced by dampening and supercalendering. Polycoated liners for double coated tapes and transfer tapes are made of paper or kraft paper that is coated with a polymer for easier release. For more information on coating or carrier material please read the Adhesive Tape Selection Guide.

Tape Specifications

When selecting tapes, there are several important specifications to consider. Physical properties include peel strength, tensile strength, elongation, temperature resistance, and dielectric strength.

Size of Tape

• Width- The breadth between predetermined edges of a tape, film or laminate.
• Thickness- Thickness is the distance from one surface of a tape, film, or laminate backing or adhesive to the other. It is usually expressed in mils or thousandths of an inch and is measured under slight pressure with a special gauge

Conversion calculators for tape specifications from Adchem are available online.

Features

Double sided and tranfer tapes are avialable with features to improve function in specific applications.

Applications

Both doublesided and transfer tapes are compatible with specific types of substrates. These include ceramics and glass, concrete and masonry, composite materials, foam, porous surfaces, leather, metal, paper and paperboard, plastic, rubber and elastomeric materials, textiles and fabric, or wood and wood products.

Resources

Adhesive Tapes Specification Guide

Foam Bonding Tapes Specification Guide

Image Credits:

R.S. Hughes | Pressure Sensitive Tape Council