Adhesive Tape Defined:
We all know and understand adhesive tapes are used for holding two surfaces together. Wikipedia defines adhesive tape as one of many varieties of backing materials coated with an adhesive. However, IHS Engineering defines adhesive tape as assembling objects or materials together using a sticky chemical bond verses using mechanical fastening, adhesive bonding, soldering, welding and/or 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 tapes 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.
Adhesive Tape Composition:
The composition of adhesive tapes typically consist of a material called a backing or carrier (paper, plastic film, cloth, foam, foil, etc.) and is then coated with an adhesive and possibly a release liner. This adhesive-coated material is then wound up to form a large jumbo roll. The jumbo roll is then split into narrow bands creating several rolls of tapes. Each roll and it’s composition contains unique properties and performance for a wide variety of conditions, which can be tailored to specific applications and functions.
Materials Used For The Backing Or Carrier:
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. Below is a list of the most popular backing/carrier options:
- Paper: Paper or flat back tape products have a paper backing.
- Cloth: Cloth products incorporate woven cloth or a fabric layer(s) for reinforcement, improved strength, heat resistance or electrical properties.
- Felt: Felt or non-woven tape, film or laminates are applied to substrates to prevent scratching.
- Foam: Adhesive-coated polyolefin foams include an adhesive that is protected by a liner in the form of a tape, film or laminate.
- Metal Foil: Metal foil tapes have aluminum, aluminum-reinforced and lead backings.
- Plastic Film/Polymer: Plastic products incorporate one or more plastic layers, or consist of plastic film or sheets that can be clear or colored, printed or plain, single-layered or multilayered, and combined with materials such as aluminum and paper. There are two general categories of plastics: thermoplastics and thermosets.
- PET/Polyester: Polyethylene teraphthalate (PET)/polyester products use a PET or polyester backing in the form of tape, film or laminate.
- Polyimide: Polyimide film (aka Kapton® tape) maintains excellent physical, mechanical, chemical and electrical properties over a wide range of physical environments. Polyimide tape is made of polyimide film and a heat-resistant, silicone adhesive. Polyimide films are very useful substrates for the manufacture of flexible circuit materials.
- PVC/Vinyl: Polyvinyl chloride (PVC)/vinyl products use a vinyl or PVC backing in the form of a tape, film or laminate.
- Rubber: Products use a rubber backing in the form of a tape, film or laminate.
- Silicone: Products use a silicone backing in the form of a tape, film or laminate.
- Acrylic Films: Acrylic films are plastic or thermoplastic resin films manufactured using polymethyl methacrylate (PMMA) or polymethyl-2-methylpropanoate. Acrylic films have good optical properties (clarity) and are UV stable.
- Glass/Fiberglass: Tape and film products are reinforced with fiberglass, fiberglass composite material or a glass layer.
- Filament: Filament is generically referred to as strapping tape. Filament tape draws its strength from thousands of individual filaments woven into yarns that are embedded in adhesive on the tape’s backing.
- Fluoropolymer/PTFE/PVDF: Fluoropolymer films, layers or coatings consist of plastics such as polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF). Fluoropolymer coatings are used in applications that require superior chemical resistance, good dielectric properties and water and stain repellent characteristics. Fluoropolymers are also used in applications where the material handled must not stick to the belt, fabric or laminate. Polytetrafluoroethylene (PTFE) is an insoluble compound that exhibits a high degree of chemical resistance and a low coefficient of friction.
Types of Adhesives Used In The Construction Of Tape:
Selecting the correct tape for the job requires a good understanding of the adhesive being used to coat the backing or carrier. 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. Furthermore, some adhesives are pressure sensitive, thermally activated or require moisture. Others, such as latex gums, adhere to themselves. Hot melt and thermoset adhesives are commonly available.
- Acrylic: Acrylic adhesives provide excellent environmental resistance and faster setting times than other resin systems.
- Epoxy: Epoxy resins are adhesives that exhibit high strength and low shrinkage during curing. Epoxies are known for their toughness and resistance to chemical and environmental damage.
- Rubber: Rubber-based adhesives provide highly flexible bonds and are usually based on butadiene-styrene, butyl, polyisobutylene or nitrile compounds.
- Silicone: Silicone adhesives and sealants have a high degree of flexibility and very high temperature resistance.
Major Categories Used To Describe Adhesive Tapes:
- Pressure sensitive adhesives (PSAs) are tacky at room temperature in dry form. They adhere firmly to a variety of dissimilar surfaces upon contact, requiring only the application of finger or hand pressure. PSAs do not require water, solvent or heat activation in order to exert a strong adhesive force on materials such as paper, plastic, glass, wood, cement and metal. PSAs have a sufficiently cohesive holding and elastic nature so that despite their aggressive tackiness, they usually can be manipulated by hand. Pressure sensitive tapes need pressure to ensure bonding. The recommended bonding pressure is 14.5 – 29 psi =^ 10 – 20 N/cm². The pressure is needed to ensure that the tape comes in close contact to the surface so that the physical forces between the adhesive and the surface can build up. The tape should be applied at moderate temperatures between 59º F and 95º F. Lower temperatures might lead to insufficient “wetting” (coverage) of the adhesive on the substrate. Extremely high temperatures might cause the tape to stretch when being applied, which could create additional stress in the final application.
- Heat activated tape is usually tack-free until it is activated by a heat source. It requires a defined period of time at elevated temperatures (normally 180˚F or higher) to achieve final bonding strength. Heat-activated adhesive coating allows aggressive bonding to hard-to-bond surfaces such as rubber, EPDM, PU and PVC-based plastic materials. And can be made of different carriers; foam, film, and tissue suitable for different types of applications. Selecting the right heat-activated adhesive often involves engineering specification.
- Water activated tape, gummed paper tape or gummed tape is starch- or sometimes animal glue-based adhesive on a kraft paper backing which becomes sticky when moistened. Water activated tape is used for closing and sealing boxes. Before closing corrugated fiberboard boxes, the tape is wetted or remoistened, activated by water.
- Non-adhesive tapes, films or laminates do not have an applied adhesive but may be self-adhering. PTFE thread-sealing tape is a type of non-adhesive tape.
The majority of the above information has been supplied by IHS Engineering 360. If you would like to view the original article, you can go to Globalspec.com
For more information on tape, check out our other pages on Adhesive Tapes:
Adhesive Tape Solutions:
- Cloth Tapes (Duct Tape and Gaffers Tape)
- Double Sided / Double Coated Tapes (Carpet, Cloth, Film, Paper, Transfer, Tissue)
- Foam Tapes (Double Sided and Polyethylene)
- Foil Tapes (Aluminum and Copper Foil)
- Packaging Tapes (Carton Sealing, Gummed, Label Protection)
- Paper Tapes (Masking, Kraft Paper, Protective Paper)
- Safety Tapes (Barricade, Hazard Stripe, Non-skid, Reflective)
- Specialty Film Tapes (Phosphorescent, Protective, Polyimide, PTFE, Splicing, UHMW)
- Strapping Tapes (Filament, Stretch Film, Banding)
- Vinyl Tapes (Electrical, Pipewrap, Vinyl and Electroplating)
- Tape Dispensers