- SPECIAL REPORTS
Single coated pressure sensitive adhesive (PSA) films and tapes are in high demand for automotive wire harness assembly. Natural rubber, synthetic rubber, acrylic and silicone adhesives are applied to specialty backings and carriers, such as films, foams and woven materials, to provide products that meet a variety of requirements.
Just a fraction of the total component cost, PSA tapes are critical to cost-effective automotive wire harness assembly. Annually, more than 1.65 billion square feet of wire harness tape is used by the automotive industry around the world.
The average vehicle’s wire harness system consists of approximately 3,500 linear feet of wire and runs from the engine compartment through the passenger area to the trunk. These distinct environments require PSAs with diverse performance capabilities. For example, tapes used in the engine compartment must resist fluids and high temperatures. Harnesses in the interior instrument panel, door panel and overhead areas require tapes that attenuate noise, vibration and harshness, to minimize squeeks and rattles caused by wire harness movement at high speeds.
Temperature is a major concern in automotive applications. For wire harness assembly, automotive temperatures are typically segmented into four ranges. T1 applications do not exceed 85 C. T2 applications range from 86 to 105 C. T3 includes temperatures ranging from 106 to 125 C. And T4 applications involve temperatures of 126 to 150 C.
Generally, PSA tapes that use rubber and modified rubber adhesives are best for T1 and T2 applications. Acrylic adhesives perform well in the T3 temperature range. Silicones are ideal for temperatures of T4 and higher.
Several types of backings are used on automotive wire harness tapes. Backing materials are selected based on the requirements of the application. Common backings include PVC, cotton cloth, coated cloth, felt, polyester cloth and glass cloth. Some backings and adhesive systems are also flame-retardant.
PVC tapes consist of two types: adhesive-coated PVC and non-adhesive coated or dry vinyl materials. Economical and widely used, dry vinyl materials are common in under-carpet interior applications, where environmental conditions are mild and the temperature rating is T1. Adhesive-coated PVC is widely used for termination and clip retention, where squeak and rattle issues are not a concern.
Cloth tapes provide the most economical squeak and rattle protection and are used for clip retention and harness wrapping inside doors, instrument panels and overhead areas. Coated cloth tapes are used for splice protection of wire terminations and breakouts, due to their high moisture resistance. The latest cloth tapes provide significantly improved abrasion resistance compared with PVC tapes. Flame-retardant cloth tapes offer performance benefits in engine compartment applications.
PSAs made of felt and non-woven materials provide the greatest noise protection, but are also the most expensive. They are used sparingly in applications that require extreme quiet, such as instrument panels and overhead harnesses in luxury vehicles.
Glass cloth tapes coated with high performance rubber or silicone adhesives deliver extreme abrasion or heat resistance. Some high temperature tapes use a glass cloth and foil laminate and a silicone adhesive for maximum temperature resistance.
Automotive recycling is on the forefront in a number of countries around the world, with the preferred method of wire harness recycling being incineration. While current generation wire harness tapes will produce acid gasses or toxins if burned, next generation halogen-free harness tapes are designed to facilitate recycling.
The PSA tapes for automotive harness assembly are selected based on the application, its location within the vehicle, and performance requirements. Tape selection is done by the harness manufacturer, conforming to OEM specifications, to ensure reliable vehicle operation and safety for the life of the vehicle.