5mm uhmw polyethylene sheet for HDPEpbuilding-Custom 5mm-25mm black polyethylene plastic sheet 5mm price - uhmw-sheets.com High Density Polyethylene (HDPE) Sheet. This sheet can be heat formed, shaped, and welded to fabricate ducts, hoods, and much more. The material cannot be cemented, but it is easily welded with a plastic welder.