Plastic may not be strongest material but it’s certainly up there, especially when it has been expertly welded. Bonding plastic can be tough and many industries use industrial plastic welder kits to bond two pieces of plastic together.
Sometimes Industrial welders will use hot air to preheat plastics but radiant heat is often provided by more professional systems. For the most basic of jobs, a starter pack with a starter pack of ABS welding rods can be used but this is not the type of machine you’d want to use on a day to day basis but it can do the job, especial if you’re extremely gifted.
There is definitely an art to plastic welding, and it’s an acquired skill that takes time and lots of practice but there are professional welding machines out there to assist you.