It seems lots of the front spoilers / splitters are made of this, and they are the first thing to find those 'little' obstructions as we travel about. I purchased an aftermarket ABS splitter for the car some time ago and had the misfortune of removing a sizeable chunk. I was lucky in that it came out in a single piece, and that I located it. I thought it was doomed and purchased a replacement, but needed to do a quick repair just to get to a show the next weekend before it arrived. I had nothing to lose, so I got some ABS pipe cement from Ace Hardware and glued the piece in. I didn't take any photos of the process because A) I was in a hurry and B) I was fairly skepticle it would work. The glue is rather messy, so it attached the piece securely but was very noticable at the seems and where it smeared when I tried to wipe it off. I had a thought about a fix and the result worked out very well.
I removed the splitter and used the ABS glue like you would bondo. As it sets up it really becomes part of the original plastic, so it sands smooth with no seams. The sanded parts are pretty obvious compared to the original texture, so I sprayed the whole thing with Rustoleum bedliner (fairly smooth) and you can't even see the repair. I can take a photo of the finished repair if anyone is interested, but it really did come out pretty good.
I removed the splitter and used the ABS glue like you would bondo. As it sets up it really becomes part of the original plastic, so it sands smooth with no seams. The sanded parts are pretty obvious compared to the original texture, so I sprayed the whole thing with Rustoleum bedliner (fairly smooth) and you can't even see the repair. I can take a photo of the finished repair if anyone is interested, but it really did come out pretty good.