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Bonding Body Side Moldings

Posted on 10/8/2012 8:01:26 AM By Sandy Niks
  

Last time we reviewed a structural bonding procedure for attaching exterior body panels to the frame of a vehicle. Now let’s look at a non-structural application of attaching parts to the body panels. Examples of these parts for today’s discussion would be emblems and body side moldings.

The body side molding is bonded to the body panel or door after it has been painted. Assembly is done in the “final assembly” area of the plant. This is generally a cleaner environment and a clean surface to bond. Paint systems, however, have changed over the years, often necessitating new adhesive systems to bond to them with every change to the paint chemistry.  Different colors would also be tested to make certain the pigments did not interfere with boding.

The adhesives for body side moldings could be a hot melt, one-part, or two-part, but double backed pressure sensitive tapes were usually the form selected. The body side molding typically arrives in the plant as a sub-assembly with the tape adhesive already applied. A release paper would also be included, protecting the adhesive surface to be attached to the vehicle. The tape itself consists of a foam carrier impregnated with adhesive. Another tape construction will still have a foam core, but then on each side have an adhesive layer to hold the foam to the film, a film layer, then the adhesive layer for bonding to the body side molding on one side and the adhesive layer for bonding to the painted body panel on the other side. This construction allows for using different adhesives, if needed, to complete the bond to the different substrates. Emblems would also use the double-backed tapes, precut to the shape of the emblem. The marrying of the body side molding or emblem to the body panel is usually automated, ensuring consistent location and applied pressure necessary to complete the bonding process.  The foam core also facilitates bonding the flexible body side moldings to the body side panels and doors that generally have some small curvature that must be accommodated.

Evaluating tapes for these applications include tests for peel, wet-out, pluck, open time, tack, creep, and environmental exposure. Some of the relevant SAE standards include SAE J1679, Peel Strength of Soft Trim Adhesives, and J2215, Surface Match Verification Method for Pressure Sensitive Adhesively Attached Components.

For examples of adhesives used for body side moldings, see the links below. Please note that this is just a small sample of potential suppliers and does not constitute an endorsement.

LORD Fusor® Plastic Repair Systems

3M Scotch® Molding Tape



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