Poly board from H.D
 

Home Depot Cary's a 4 by 8 sheet 1/2 inch thick of poly board ,the white plastic stuff that looks just like starboard for 79 dollars a sheet, I ask them if it cuts like wood and they said it does, did anyone use it? 79 dollars is better then 200 dollars maybe more for a sheet that big

79 beats the snot outta 200 no doubt. I'll have to run over and check it out. Does it make any reference to how it holds up in sunlight?...

I did not ask them but the application is for out side so I'm thinking it's good

PVC board? Compares to "Star Light Board"

The pvc board is a lot lighter than Starboard (High density polyethylene).
There is a brand name AZEK that is $$$ but HD has a cheaper version also.

It cuts like wood. Comes in trim board sizes also. It is "foamy" so the edges are rough and exposed edges tend to hold dirt. The faces are smooth and hard. It would be a good flat surface for a dashboard, but you would have to put trim around the edges.

I used it as backing for my bolsters. Perfect for that. Used it for trim on my house too. You could build a door. Not sure if it would hold up as a deck hatch.

I wouldn't use it for a cutting board.