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November 7, 2016 - Aerospace Assembly Automotive

Types of Film Adhesives and When to Use Each One

Film adhesives consist of a thin layer of adhesive supported on a removable backing. These adhesives are high-performance bonding agents supplied in convenient, easy-to-use forms. The combination of performance and handling convenience has lead to their growing popularity across a range of markets, including:

  • Aerospace
  • Automotive
  • Assembly

Film adhesives offer various benefits:

  • Uniform and consistent adhesive application
  • Reduced material waste
  • Customized width and thickness
  • Flame retardancy

While there are certain considerations to make when choosing a film adhesive, it’s also important to understand why you would use one type over the other. Let’s take a closer look:

Types of Film Adhesives

Film adhesives can be either pressure sensitive or heat activated:

  • Pressure sensitive: can be applied using varying pressure
  • Heat activated: need to be heated in order to generate a bond

Film adhesives also can be:

  • Thermoset: a material that forms an irreversible chemical bond once it cures
  • Thermoplastic: a material that can become soft when heated and sets when cooled. Unlike thermosets, this heating/cooling process is repeatable multiple times.

For more detail on thermosets and thermoplastics, view our Adhesive Education Series blog.

  • Flame retardant: a material containing additives, which slow down the spread of flames

Understanding Application Conditions

It’s important to understand what conditions the film adhesive will be exposed to upon application. For example, if the end-use application requires high temperature resistance, this condition will assist in determining which adhesive will perform best in that environment.

film adhesives

Understanding Substrate Compatibility

Certain types of films bond to some substrates better than others. Common substrates film adhesives bond well to include:

  • Fabric
  • Leather
  • Urethane foam
  • Rubber
  • PVF (e.g., Tedlar®)
  • PVDF (e.g. Kynar®)
  • Aluminum
  • Aramid honeycomb core
  • Fiberglass

It’s important to understand a film adhesive’s base polymer to determine substrate compatibility. A polyester film is likely to bond better to a substrate of a similar, polyester composition.

Choosing a Pressure Sensitive Adhesive (PSA)

PSAs are easy to use; no heat or equipment is needed for a bond to be made. Able to accommodate various application conditions, PSAs work well as attachment or mounting adhesives in particular. PSAs are thermoplastic, which means they are flexible when cured.

Choosing a Heat Activated Adhesive

Heat activated adhesives are generally not tacky at ambient conditions, so heat is needed to activate the adhesive bond. These film adhesives can be used in continuous processes or cut into sheets, enabling precise layer placement prior to bonding in piecemeal applications.

Heat activated film adhesives that are thermoset offer increased strength as well as higher heat and chemical resistance. Due to the cross-linking that takes place when a thermoset film adhesive is cured, there can be increased rigidity compared to a thermoplastic film adhesive.

Film adhesives

Knowing When Flame Retardancy is Needed

Both PSA and heat activated film adhesives can be formulated for flame retardancy. Flame retardancy is often a desirable feature across various applications including:

  • Specialty safety clothing
  • Seat cushions
  • Transportation applications (aerospace, rail and automotive interiors)

While the added flame retardancy can be beneficial, it is not always needed when choosing a film adhesive. It’s important to understand the capabilities of the two substrates being bonded together. A flame retardant adhesive can often help a finished product pass industry standards, such as FAR or DIN, even though the substrates being bonding together may not pass on their own. However, if the substrates themselves exhibit sufficient flame retardancy, a non-flame retardant adhesive will still enable the finished product to pass.

Bostik manufactures a line of film adhesives covering a variety of performance properties and allowing customers to achieve results unattainable with other adhesive technologies. Two products of note include:

  • F10-316: a heat activated, thermoset, polyester film adhesive with a low activation temperature and good flow properties.F14-588: a pressure sensitive, thermoplastic flame retardant film that offers great potential for applications where high shear strength and flame retardancy are required.

For more information on our film adhesives, call 800-7-BOSTIK, or visit www.bostik.com/us.

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