Talk:Bondline
[Bob Steward writes] To repair cracks and chips in the interior ABS plastic (AKA "Royalite") trim, the Maintenance Manual gives a procedure that I've had good success with. The MM recommends using MEK (Methyl Ethyl Ketone) solvent as a plastic welding glue. MEK is available at larger hardware stores in the paint department.
The process is to paint MEK on the plastic edges and allow the solvent to soften the plastic, and then press the edges together and let the solvent flash off, leaving a joint that is nearly as strong as the original material. To fill small voids a paste of ABS plastic and MEK can be prepared and painted on in coats to fill the missing area. Small brushes are recommended. A metal or glass container to hold the solvent is needed, since it will attack most plastics.
You can obtain a pre-made ABS paste from Lowes and other hardware stores in the plumbing section. At Lowes its a blue can and it says "ABS Cement" on it. If you look at the ingredients on the label it will say that it is ABS and MEK. There are also several plastic pipe cements in the same area. Beware of any that list other types of plastic such as PVC or CPVC, as these will be just solvents with no ABS filler included. I've found that the pre-made ABS cement is best applied after a coat of MEK to soften the base plastic. This gets the ABS of the base part ready to fuse with the ABS in solution.
With a little patience and some scrap ABS sheet, I've created doublers to glue on the back of cracked and chipped areas, especially helpful to back up screw holes that have cracked out or lost a pie wedge of plastic between the screw hole and the edge of the part. These doublers adhere very well if you paint the back of the part with MEK and wait for the plastic to soften, and paint the face of the doubler, and then re-wet the area on the part where you want to bond the doubler and press them together wet. Some Cleco clamps are helpful to hold the parts while they flash the solvent and solidify. Having the clamps lets you do several repairs without having to wait between each repair for the last one to become firm enough that it doesn't pop loose.
After a doubler is bonded on the back and cured, you can fill the area where the chunk was missing by painting coats on the front side. Just as with paint, several light coats is much better than fewer heavy coats, and you want to let them dry between coats. After 2 coats it probably will need to sit overnight to allow the solvent to evaporate from within the layers. If you have filled the area sufficiently, then you can sand the surface to smooth it and level it with the surrounding area.
On really big projects, especially external parts like elevator tips or tail cones, you might need to apply a larger doubler or hold a big crack in alignment. You can use the ABS just like aluminum sheet and make doublers to go behind cracks and hold the doublers with clecos in a series of rivet holes. The holes can be filled later and the part sanded smooth before painting. Carefully done, parts that would have seemed unsalvagable can be returned to service and look just like new after sanding smooth and repainting.
Speaking of repainting, the interior plastic trim can be made to look like new with a coat of "vinyl dye". This is just a paint that is formulated to bond to the plastic. There are several brands, some available in rattle cans and some available in bulk for a spray gun. Automotive paint supply stores that serve the body shops will be able to mix the bulk type in a rainbow of colors, and many auto parts stores carry the rattle can variety in a half dozen colors.
