That's what I used to manufacture.
It's made from recycled milk bottles.
I doubt it's stable enough to hold up under that weight repeatedly.

When used to build decks or picnic tables, it needs a lot of supporting structure. The wood joist at 16" on center will hold up a 2X6 board for a long time. When made into benches and pic nic tables it needs a metal sub-frame. Even then it can start to sag. Especially if left in the sun.