Have 90 degree one inch diam. grey plastic tubing 90 deg. bend.

Want to bend it some more; hopefully to 180 degrees (or close to that)
to make shape of a 'J'.

Any suggestions. Heat gun? Flame? Oven? Also will it tend to flatten
as metal pipe does when bent further?

If this doesn't work could I use something else; that newer PEX water
piping for example?

Help/advice appreciated. TIA