Foam Bonding Tapes Information
Foam bonding tapes are designed for the adhesive joining of foam materials. They use adhesives that are formulated for specific types of foams and substrates. Foam bonding tape is an important component in any application using foam products because failure of the bonding may cause the entire product to fail.
Selecting foam bonding tapes requires an analysis of foam type and the application requirements. There are several important factors to consider when choosing a foam bonding tape.
- What the materials are
- If the bond is structural or non-structural
- If the surface needs to be prepared
- The stresses and environmental conditions of the applications
Selecting the right foam bonding tape first requires analysis of the foam material, also known as the substrate that the tape will be bonding. There are many different types of foam materials which have a variety of properties based on their application. An industrial buyer should consider the chemical properties as well as the surface texture, surface energy, and compressibility.
Chemical resistance- Chemical resistance describes the amount and types of chemicals the foam can tolerate before breaking down. Some foams are designed to be resistant to damage by acids, alkalies, general chemicals, and oils.
Surface texture- The surface texture of foam can range from very rough to very smooth. This can affect how the tape bonds to the foam and the quality of the seal it creates. Rougher surfaces will usually need a thicker adhesive because the adhesive will sink into the surface of the material, but care should always be taken to test the surface so that the right adhesive is used.
Surface energy- Surface energy describes the strength of attraction. The higher the surface energy, the greater the attraction and vice versa. Adhesion is defined as the molecular attraction between unlike materials. It is similar to magnetic force. When a material has a high surface energy, a liquid will spread across the material's surface. Materials with high surface energy and good adhesion are metals, polyester, Kapton, PVC, and ABS. When a material has a low surface energy, liquid will forms beads that can't flow. Materials will low surface energy or poor adhesion include polystyrene, acetal, powder paint, Teflon, and polyethylene.
Compressibility- Compressibility is the amount of pressure which can be applied to the foam before the material breaks down. This is especially important for pressure sensitive adhesives (PSA) which are applied to the foam with pressure. A foam with high compressibility will have good memory characteristics and can withstand a significant amount of pressure.
Open Cell vs. Closed Cell Foam
An important distinguishing factor for foam is whether it is open cell or closed cell design. Open cell foams have pores or cells that are interconnected and open to an external surface. Air is able to move freely between the cell walls so the foam is able to return to its original position after pressure has been applied. They are best used for filtration-type applications as well as in applications which require high compressibility since air is less likely to leak from an open cell foam. Closed cells foams have pores or cells that are not interconnected and are sealed off to an external surface. The bubbles of air in the foam have cells walls around them so that when pressure is applied to the foam, the air is compressed and the foam can return to its original shape once the pressure is removed and air decompresses. However, eventually the air can leak out of the cells causing the foam to lose some compressibility. They are best used as floatation devices and as insoles of sneakers.
Image Credit: Mass Energy Lab. Inc.
Adhesion is the ability to stick or bond to a substrate. The adhesive on the foam bonding tape has unique properties which allow it to join foam with another material. In order to select the appropriate adhesive for the application, there are additional factors which should be considered. Foam bonding 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
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 are applied as a liquid or high viscosity paste. Hot melt adhesives are available as fast set, delayed set, and pressure sensitive types. This type of adhesive can be repeatably soften and melted by heat, and hardened or set by cooling and are available at various tackiness levels.
Video Credit: Gluemachinery / CC BY-SA 4.0
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 leave 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 adhesive has 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.
Solvents can cause adhesive swelling, softening, or dissolve the adhesive all together.
The carrier or backing material for foam bonding 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.
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Cloth: Woven Fabric, Non-woven- Cloth products incorporate woven cloth or a fabric layer(s) for reinforcement, improved strength, heat resistance, or electrical properties. Non-woven-Felt or non-woven tape, film, or laminates are applied to substrates to prevent scratching.
Acrylic- Acrylic films are plastic or thermoplastic resin films manufactured using polymethyl methacrylate (PMMA) or polymethyl-2-methylpropanoate. PMMA resins are the result of polymerization of acrylic acid derivatives or other acrylate compounds such as esters of acrylic acid, methacrylic acid, acrylonitrile, and their copolymers. Acrylic films have good optical properties (clarity) and are UV stable. Plexiglas® (Altofina Chemicals, Inc) is a common acrylic sheet and film material.
Glass / fiberglass- Tape and film products are reinforced with fiberglass, fiberglass composite material, or a glass layer. High strength film or fiberglass backing is not typically used in foam bonding because the foam material is relatively low in strength compared to their full density counterparts.
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- 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. It is sometimes marketed in proprietary classes of materials such as Teflon®, a registered trademark of DuPont Dow Elastomers.
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
Paper- Paper or flatback products have a paper backing.
PET / polyester- Polyethylene teraphthalate (PET / polyester products use a PET or polyester backing in the form of tape, film, or laminate.
Plastic / 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.
Polyimide (e.g., Kapton®)-Polyimide film maintains excellent physical, mechanical, chemical, and electrical properties over a wide range of physical environments. Kapton® tape is made of polyimide film and a heat-resistant, silicone adhesive. Kapton is a registered trademark of DuPont Teijin Films. 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.
Foam bonding tape comes in a wide variety of sizes. The size needed depends on the size of the application.
The width of the tape will depend on the width of the substrates being taped.
The tape thickness is the distance from one surface of the tape to the other. It's usually expressed in mils or thousandths of an inch with the use of a slight pressure gauge, and includes all the layers including the liner or backing, adhesive layer, and any material separating the adhesive layers.
Image Credit: CCT
Peel strength- The peel or adhesion strength is the force required to separate two bonded surfaces. The peel test measures adhesion and a peel value indicates how strongly the adhesive has bonded, or adhered, to a substrate. The peel test measures both the initial and ultimate adhesion. Initial adhesion indicates how well the adhesive works over a short period of time (seconds or minutes). The ultimate adhesion refers to the bond strength over a longer period of time (72 hours). The peel test tests the adhesive's reaction during a 90 degree peel and a 180 degree (back over itself) peel.
Video Credit: ADMETTestSystems / CC BY-SA 4.0
Temperature resistance- The temperature resistance is the maximum temperature the products can withstand. High temperatures can cause the adhesive to soften, and reduce the shear and cohesive strength of the material. Low temperatures can make the adhesive brittle which causes cracking and an increase in shock sensitivity.
In terms of features, foam bonding tapes can be:
Single-sided or double-sided- Single-sided only have one side with the adhesive layer. Double-sided tape has both sides of the backing or carrier covered with adhesive. Two different adhesives can be used on each side which is useful for applications that involve bonding together very dissimilar materials.
Dielectric- Dielectric tapes are used as membrane dielectrics in multilayer capacitors. The insulating tape consists of an acrylic polymer mixed with a dielectric solid.
Electrically conductive- Electrically conductive products can conduct electricity and provide protection from electrostatic discharge.
Transparent- Transparent products allow the transmission of light. A tape is rated transparent if 10-point type can be read when the tape is applied directly over it.
Transfer tape- Transfer tapes are versatile products that consist of a thin adhesive film without a carrier or backing. They can be transferred to most dry surfaces from a peel-away release liner.
Anti-static or ESD control products- Foam bonding tapes that control electrostatic discharge (ESD) or provide shielding against electromagnetic interference (EMI) and radio frequency interference (RFI).
Permanent or removable- Permanent tapes cannot be removed once applied and bonded. Removable adhesive and be removed without damaging the substrate. Repositionable tapes can be adjusted as they form a bond.
Suitable for outdoor use- Outdoor use tapes are resistant to damages caused by UV light and weather conditions such as rain, snow, or wind.
Foam bonding tape can be used when the application requires joining of dissimilar foams. In this application a double coated tape with two different adhesives on each the backing can be used that provides optimal bonding for each type of foam component. Transfer adhesives consisting of a single type of adhesive would be fine for applications bonding similar types of foam materials.
Applications for foam bonding tapes include aerospace, automotive, building and construction, biotech and pharmaceutical, cable, electrical and electronics, packaging, plumbing, printing, and splicing. Foam bonding tapes can also be used with muntin bonding and other glazing applications.
Foam bonding tapes are available that are manufactured to the testing standards of the Pressure Sensitive Tape Council (PSTC) or the American Society for Testing Materials (ASTM) .