Adhesive tapes are used to assemble materials or parts together using a sticky chemical bond. They are an alternative to other assembly methods such as mechanical assembly (press fit, snap fit, etc.), mechanical fastening, adhesive bonding, soldering, welding and brazing.

Adhesive tape has the advantage of lower temperature applications compared to soldering, welding and brazing. It also does not require pre-drilled and/or pretapped holes or welded-on studs on the components like is needed for mechanical fastening.

Adhesive tape can be easier for production operation and automation compared to processes using a liquid adhesive, which must be sprayed, rolled or otherwise dispensed onto the parts before bonding. In adhesive tapes, the adhesive is preapplied to a uniform backing material that enables the tape to be handled with web processing equipment. The disadvantage of adhesive tape is its inferior strength compared to brazing, welding or mechanical fastening. The lower bond strengths may not meet more demanding design requirements.

Manufacturing Process

Adhesive tape production - Image credit: Made How

Adhesive tapes are made by coating a backing or carrier (paper, plastic film, cloth, foam or foil) with an adhesive on a web or roll coater. The adhesive-coated tape is wound up to form a large jumbo roll. The jumbo roll is then split into narrow bands, which are wound on individual cores to produce the retail or commercial size rolls of tape.

Operation

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 - paper vs. film vs. metal foil vs. fiberglass cloth.

Air setting or film drying materials form a bond or "harden" by evaporating water or an organic solvent. Inorganic binders or cements are sometimes air setting. Refractory-type products may develop strong bonds after firing. Many pastes and gum adhesives are film-drying.

Anaerobic adhesives cure in the absence of air or oxygen. They are designed for fastening applications in which a tight seal must be formed without light, heat 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. Most hot melt adhesives are solvent-free thermoplastics that melt or drop in viscosity above 180°F and then rapidly set upon cooling. They are used in a variety of manufacturing processes, including bookbinding, woodworking, construction, product assembly and box and carton heat sealing. Hot melt adhesive technology stems from the previous use of molten wax for bonding. Thermoplastic systems were introduced to satisfy performance needs. Typically, a pure hot melt system will not have the heat resistance of two-part, catalyst or thermoset adhesives. Hybrid hot melt systems are available which exhibit a degree of reactive curing. Polyethylenes, polyamides and ethylene-vinyl acetates are common types of hot melt adhesives. Heat activated adhesives become sticky or tacky when warmed and are used in contact or PSA-type applications.

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. Cured thermoset resins also generally have higher resistance to heat than thermoplastics, but cannot be melted down and reprocessed. Phenolic, melamine and urea formaldehyde resins are thermosetting adhesives that offer strong bonds and good resistance to high temperatures.

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. It results in greatly increased strength, stability and elasticity in rubber-like materials. The vulcanizing agent is a crosslinking compound or catalyst. Silicones use moisture, acetic acid and other compounds as curing or vulcanizing agents.

Pressure sensitive adhesives (PSA) adhere to most surfaces with very slight pressure and retain their tackiness. PSAs are available in solvent and latex or water-based forms. Pressure sensitive adhesives are often based on non-crosslinked rubber adhesives, acrylics or polyurethanes. 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. One disadvantage of UV curing adhesives is the requirement that one substrate is UV transparent. Some UV resin systems employ a secondary curing mechanism to complete curing of adhesive regions shielded from the UV light. EB curable adhesives use electron beam radiation to cure or initiate curing. The electron beam can penetrate through material that is opaque to UV light.

Reactive/moisture cured resins are single-component adhesives that are applied in the same way as hot-melt adhesives. The resins react with moisture to crosslink and polymerize, thus resulting in a cured material. Polyurethane reactants (PUR) are examples of this type of technology. Certain silicones and cyanoacrylates also use a reaction with moisture or water to cure the adhesive or sealant.

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.

Other unlisted, specialty, proprietary technologies or cure types.

Composition

Adhesive tapes typically consist of an adhesive-coated backing called a carrier. Single-sided tape is used to attach overlapping or adjoining materials where the tape is used to splice or seam the materials together. 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. Transfer tape can also join parts between mating surfaces in a back-to-back or butt joint fashion.

Adhesive Coating Types

Selecting adhesive tapes and films requires an analysis of coating types. Acrylic adhesives provide excellent environmental resistance. Epoxy resins exhibit high strength and low shrinkage during curing. Polyurethane (PUR) and isocyanate adhesives provide excellent flexibility, impact resistance and durability. Silicone adhesives have a very high temperature resistance. Rubber-based adhesives provide highly flexible bonds. Pressure sensitive adhesives (PSA) are tacky at room temperature in a dry (solvent-free) form; they adhere firmly to a variety of surfaces upon contact, requiring only the application of finger or hand pressure. Some adhesives are thermally activated or require moisture. Others, such as latex gums, adhere to themselves. Hot melt and thermoset adhesives are commonly available.

Adhesive Coating Options

Backing/Carrier Types

Adhesive tapes and films vary in terms of carrier material. Films are synthetic resin adhesives that sometimes include a carrier fabric. Typically, plastic films are made of thermoplastic resins. Aluminum foil is laminated to paper or plastic films for improved strength. Electrodeposited copper foil is used in the manufacture of multilayer printed circuit boards (PCB). Transfer tape, a highly versatile product that consists of a thin adhesive film without a carrier, 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 that are usually measured in terms of points. The 12-point liner is the most common type. Other backing materials include cloth, foam, paper, plastic, rubber, silicone and urethane.

Backing/Carrier Options

Specifications

Important performance specifications for adhesive tapes include peel strength, tensile strength, temperature resistance and dielectric strength. Physical parameters include width, thickness and length.

• Temperature Resistance - The maximum temperature that products can withstand.
• Peel Strength/Adhesion - The force required to separate two bonded surfaces.
• Electrical Resistivity - The longitudinal electrical resistance (ohm-cm) of a uniform rod of unit length and unit cross-sectional area. Resistivity is the inverse of conductivity.
• Dielectric Strength - The voltage that products can withstand without allowing the passage of current.
• Width - The breadth between predetermined edges of a tape, film or laminate.
• Thickness - 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.

Features

Adhesive tapes and films are available with a variety of features. Some are chemically resistant, thermally insulating or electrically conductive. Others are permanent, removable, repositionable or protective. Safety products are reflective, highly visible and provide warnings about unsafe conditions. Weather resistant products are suitable for outdoor use. Transparent products allow the transmission of light.

Features Available

Applications

There are a variety of applications for adhesive tapes and films, as described in the table below. Some are suitable for automotive, aerospace, construction, industrial, medical or packaging applications. Others are designed for use with coated abrasives or cable ends. Electrical tape provides high voltage and heat resistance. Masking tape is used to temporarily cover bands or small areas next to an area to be painted. Duct tape is used in heating, ventilation and cooling (HVAC) applications. Adhesive tapes and films are used to splice film, build membrane switches or control panels, and join materials together in processes such as seaming or hot sealing. Products that are suitable for printing, graphics and signage applications are also available.

Applications

Resources

Made How - Cellophane Tape

Science Channel How it's Made via Youtube

3M - Industrial Tapes

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3M Industrial Adhesives and Tapes | Panduit