This show what kind of plastic it is. This is SAAB, PP+EPDM-M10
In this case, there are three components in the plastic, that means you have to glue.
If it´s 2 components in the plastic, for example: PP+EPDM , you can weld it.
The M10 means there are 10% of some filling material, and that can´t be melted. So no welding.
Here is the damage, a hole.
First heat treatment with a IR heater, to make the plastic soft
Here I roll the back of the bumper to get the dent out.
Then I sand the back with P240 sanding paper.
Clean the area with 3M Surface cleaner, it´s a alcohol-based cleaner.
Spray on a Plastic Primer.And let dry 5 minutes or more.
In order to strengthen the glue on the backside I use a glass fiber net.
Add glue. I use Terokal-9225 from Teroson alot, works to 90% of the plastics that are in cars.
Let dry a couple of hours.
Now the outside. Sand with P240 and grind a ditch in the crack, then clean the same way as before.
Plastic Primer.
Glue. You can choose to just glue the crack, and then shape it with bondo.
I choose glue for both the crack and to chape
I let it dry till the next day to be sure it harden enugh to chape it with a rasp.
And sand it with P240.
Clean and spray on plastic adhesion promoter and 3 coats (it´s about 150-200μ) of MaxMeyer Filler 0310.
After I hour in 70ºc, it´s ready to prepare for paint.
After sanded with P600.
Painted.
