Polypropylene Bumpers

Three types of damaged bumpers are considered serviceable:

• A bumper with a hole less than 50mm (1.97 inches) in diameter.
• A bumper with a crack less than 100mm (3.94 inches) in length.
• A bumper with a crack less than 100mm (3.94 inches) in length that is less than half of the width of the bumper.

Although a bumper which has been damaged greater than this could also be serviced, it should be replaced with a new one. This is because such service would detract from the beauty and quality of the bumper due to the decrease of the adhesive strength, etc. In addition, such service is not considered reasonable in terms of work load.

Repair polypropylene bumpers having flaws that have reached the surface of the polypropylene and are too serious to be restored by painting.

1. Cut the rough edges around the flaw with a knife to make it smooth. Sand the area with a sander to make an angle of about 45 degrees.

    CAUTION: Disconnect the battery ground cable (14301) before using any electric welding equipment.

2. Weld damaged area.
   • For service of a cracked area, melt the crack together using Rotunda Airless Plastic Welder 107-01250 or equivalent.
   • For repair of a hole, degrease the area and the reverse side of the damaged area. Install aluminum tape on reverse side of damaged area.

   NOTE: Heat only the shaded area to melt it.

3. Melt the polypropylene welding rod with Rotunda Airless Plastic Welder 107-01250 or equivalent, and deposit it in the cracked area.

   Take care not to excessively melt the welding rod. If the part is welded with the welding rod melted like jelly, the welding strength will be lowered.

   Operate a heat gun 12-51mm (0.5-2.0 inches) away from the part that will be welded.

   Do not move the welding rod until the welded part cools.

   NOTE: Do not sand part continuously.

4. Sand the surface of the polypropylene little by little, since it is easily melted even by the abrasion heat. If melted, remove the melted area. Sand the areas to which service agent will be applied.

5. Apply polypropylene primer uniformly to an area larger than the serviced area with a brush. It will take about 10 minutes to dry at 20° C (68°F).

   NOTE: When mixing the main and stiffening agents, be careful not to allow bubbles to form.

6. Mix the main agent and the stiffening agent in a ratio of one to one. Apply the mixed service agent to the damaged area.

   Since the servicing agent hardens fast (about five minutes), proceed with the work immediately after mixing the agents.

   It will take about 30 minutes to dry at 20°C (68°F) before it can be sanded.

   NOTE: If excessive force is applied to the area when sanding, the surface will not become smooth.

7. Sand the area with #180-#240 sandpaper.

   If there is fuzz around the repaired area, melt it by heating it slightly with a heat gun.

8. Degrease the painted surface.

   NOTE: Polypropylene primer will dissolve, even after drying, if it is wiped with solvent. Use only water to clean.

9. Dry the part.

10. Add the softener to the urethane primer surfacer and spray it on the service area.

11. Air dry at 20°C (68°F) for 8 hours.

    Force dry at 60°C (140°F) for 1 hour.

12. Lightly sand the area on which the primer surfacer is sprayed and the complete surface of the bumper with #400-#600 sandpaper. Do not expose the surface of the polypropylene. (Wet sanding or dry sanding is acceptable.)

13. Wipe the complete surface of the bumper with degreasing agent. Quickly wipe the surface with a clean rag to degrease it.

    NOTE: The paint for servicing a polypropylene bumper adheres poorly to a urethane bumper. Therefore, be sure to use only urethane primer for a urethane bumper and polypropylene primer for a polypropylene bumper.

14. Apply a matching coat of paint to the polypropylene bumper.

    Other paints for servicing a polypropylene bumper are the same as those for the urethane bumper.

15. Air dry at 20°C (68°F) for 8 hours.

    NOTE: Let the part air-dry when possible, since force drying could cause bubbles in the top coat.

    Force dry at 60°C (140°F) for 1 hour.