On 30 July, 14:00, PeterC wrote:

For some large pieces of PP, it's easier to hot weld it. This is quite
easy if you have a hot-air welding gun - people who do car bodywork
do.

Many years ago I had to construct a small plating line from PP - the tanks
were about 75 cm cube, IIRC. I tried a hot-air gun but it slightly charred
the PP;

You need a real hot air welder. I don't know the differences of
temperature and airflow in detail, but you can repair car bodywork
(bumpers etc) with the real one in a way that just doesn't work when
you try to hack it with a paint stripper or a heatshrink gun.