Just picked up some Zender bumpers for my MB 190e. The front one had a small bend in it on one side.



It's a catalyzed urethane, so a heat gun just causes it to bubble but still remains stiff... any ideas how to get it back into shape?

dw - have you mounted it on the car yet to see how it hangs??
It may not be as bad as you think - gravity and all.
Can you tell if it was hit and that's why it sags??
Just throwing stuff out - but you may try internal bracing to get it back close. Aluminum "angle iron" along the sag internally maybe??
If not scuff and epoxy resin / glass mat to build it back up. For me that sticks the best. Adding MORE hardner to the epoxy (10%) makes it more flexible.
Sorry I couldn't be more helpful - 80GG

What I like to try out also is this.

Grab a heat gun, some dollies or gloves, a bucket of cold water and a sponge.

Then heat the area (becareful not to melt the plastic) that is sagging or pushed in and while heating it slowly push it back out. Then once you have the shape you desire remove heat gun and quickly drench the area in cold water from both sides. This will contract the plastic but if you keep holding it in place it should hold its new shape. You man need to spend some time with it and keep repeating but this is the best thing I found to do if you dont feel like sanding and filling in the dents with filler, plastic repair, fiberglass, or whatever else you may try.

Grab a heat gun, some dollies or gloves, a bucket of cold water and a sponge.

^That'll get majority of it done^