I know its not an epoxy. Only giving examples above of inferior repairs.
Urethane Bumper Covers, TPO Bumpers Covers, ABS Parts, are not made out of the same material, that would get britle upon heating like you guys are refering to. Totally different.
#1 Reason being there is a percentage of wax in the molding mixture. This is what allows types of plastic to flex (bumper covers) When you heat wax it only becomes more pliable. When you cool wax then it become britle.
If you have a large dent in the side of a bumper cover, it gets heated and the dent will pop out. Plastic has memory. There will be an edge but it comes out. It doesnt break.
More covers are cracked in the winter time then in the summer time. There is a reason for that.
I've used platex, and every other type of plastic repair material. There is nothing out there that will meet the quality repair of thermally welding platic. Nothing. I worked on a corporate board testing all these material against each other. Not just this, but many more types of fillers, adhesion promotors, etc. All of the research we perform is not set as a standard for platic repair across the united states. Its accepted as the #1 repair with ALL insurance companies in the industry.