Adhesive Backed Material
An adhesive, also known as glue, cement, mucilage, or paste, is any non metallic substance applied to one surface, or both surfaces, of two separate items that binds them together and resists their separation. Adjectives may be used in conjunction with the word “adhesive” to describe properties based on the substance’s physical or chemical form, the type of materials joined, or conditions under which it is applied.
The use of adhesives offers many advantages over binding techniques such as sewing, mechanical fastening, thermal bonding, etc. These include the ability to bind different materials together, to distribute stress more efficiently across the joint, the cost effectiveness of an easily mechanized process, an improvement in aesthetic design, and increased design flexibility.
The adhesive is coated onto a flexible material (the backing) such as paper, foil, fabric, or plastic film (such as biaxially oriented polypropylene or polyvinyl chloride) to provide strength and protect the adhesive from degradation by environmental factors including humidity, temperature, and ultraviolet light. Backing tensile strength, elongation, stiffness, and tear resistance can be matched to the intended use of the tape. The adhesive can be bound to the backing through surface treatments, primers, heating, or UV curing.
To allow for the winding and unwinding of the tape, the backing is coated with a release agent that somewhat prevents the tape from sticking to itself or the sticking of two adhesive layers (double-sided tapes). This is accomplished by using a material that enables the easy removal of favorable interactions at the adhesive-backing or adhesive-adhesive interface, or by making both surfaces immiscible in one another. Two common materials used in polyacrylate-based adhesive tapes are fluorosilicones and vinyl carbamates. Fluorosilicones are immiscible with the polyacrylates-based adhesive whereas the long tails of vinyl carbamates form a high crystalline structure that the adhesive cannot penetrate. Furthermore, during peeling fluorosilicone release liners make no noise whereas vinyl carbamates make loud noises.
Plastic films can have the surface modified by corona treatment or plasma processing to allow increased bonding of the adhesive. A primer layer can also be used for this purpose. Some backings need to be sealed or otherwise treated prior to adhesive coating. This is especially important when the introduction of new materials into the adhesive can compromise the adhesive’s performance.
- BSR Patches
- NVH Patches
- Flocked Tape
- Cardboard / Fiberboard
- Pressure Sensitive Materials
The adhesive is largely affected by the temperature as polymeric adhesives are commonly used today. Polymeric materials used today are viscoelastic materials, which enables easy application and quick adherence to the substrate. Adhesive degradation in the bulk is largely due to temperature effects, which reduce adhesion causing delamination of the adhesive tape. Too low a temperature can cause the polymeric adhesive to enter its glass state becoming very brittle and reducing adhesion. Raising the temperature, on the other hand, causes the polymer to become more fluid and mobile. As the mobility increases, the polymer adhesion is reduced as the polymer starts to flow as opposed to adhere.
Both temperature extremes ultimately results in delamination. The ideal temperature range is largely dependent on the adhesive identity, which comes down to polymer structure. The more rigid the polymer chain is, the stronger the Intermolecular Forces between polymer chains, and the stronger the interactions between the substrate and the adhesive will ultimately result in a strong adhesion and, as a result, a higher ideal temperature range for adhesion.
That being said, in order to avoid delamination, selection of an adhesive tape needs to be based upon the conditions that the tape will experience over its lifetime. This selection process will reduce the chains of adhesive tape degradation and failure occurring during the lifetime of the tape though there is not guarantee that this process will completely avoid the possibility.