Carrying adhesion to the peak. A brief look at backings

The backing material initially has the job of holding the adhesive and the primer. It is fundamentally relatively thin, flexible and also smooth. That makes it perfectly suited for almost every application in every place of use and every design. The material itself can differ widely – and this is where it begins to play a critical role, depending on where, how long and for what purpose an adhesive tape should be used. Today’s backings are designed to withstand certain forces or to split at an exact defined force, to be optically clear or reflective, to be permeable or to function as a barrier (e.g. for humidity or oxygen), to be very thin (1.5 μm = 0.059 mils) or to be very thick (>3mm or 118 mils). Modern backings serve as gap fillers or noise dampeners, enable the tape to be machine-processed or die-cut. Due to the multiplicity of the available types of backings, it is worth discussing features and benefits of the different types.

Fabric and fleece such as cotton, viscose or PET provide mechanical advantages that make them exceptionally feasible for their specific area of application. The covering of cracks, the bundling of cables, sealing or splicing can be handled ideally with fabric and fleece as backing material.

Cotton and viscose have a high tensile strength but, in comparison to PET, are easy to rip by hand. Classical examples are adhesive tapes with fabric, such as duct tape or Gaffer tape. Cotton is a pure natural product and thus sustainable; viscose is more homogeneous and can be reproduced better. Fleece is especially supple and offers the advantage that it attenuates noise and vibrations exceptionally well.

Produced out of pulp, hemp and synthetic fibres, it has different paper qualities that appear in the adhesive tapes.

Smooth papers are in demand when adhesive tape is required for packaging or as templates for sandblasting. Creped paper with different stretching is used for masking and painter's tapes. A higher degree of “crepe” to the paper allows for easier application of the tape to curves and contours. Especially fine Japanese paper prevents paint from running under the masking tape.

The special properties of paper as a backing material are seen in the ease with which it can be ripped by hand, its good suppleness and the possibility of stretching it by up to 50 percent. It is also resistant and absorbent up to over 180° C. There are more complex paper backings which are used in the paper industry for splicing or end tabbing large paper rolls. In this application, the paper needs to be re-pulpable (dissolvable without leaving any residues in the newly produced paper).

For high temperature applications (above 200º C) or for applications that require an even higher performance than a foam adhesive tape, acrylic core backings are the ideal solution. Since they consist of an acrylate polymer, they have outstanding viscoelastic properties. This means that they are capable of balancing out material tension, distributing forces and dissipating stress. Furthermore, they can compensate for temperature-related expansion – up to triple their thickness, depending on the backing structure. In combination with very high bonding strength, acrylic core tapes are the ideal solution for the gluing of distinct surfaces such as glass on metal or metal on plastic.

As an added benefit, acrylic backings are very resistant to many environmental elements, such as sunlight, ozone, temperature, and water. These characteristics make acrylic core tapes the ideal choice for long-lasting, high-performance outdoor applications. Application examples include bonding body side mouldings to car bodies (automotive); bonding framing of flat screens (electronics); bonding glass panels to metal frames; or joining photovoltaic panels onto back rails (solar panels). These and other appropriate applications demand high-bonding strength, long-term (up to 25 years) outdoor performance, and compensation of thermal differences.