Not exactly a machining problem, but I am looking for something that can be formed into a 150mm dia tube, 300mm long, that is non-porous and sufficiently rigid to withstand local deformation. I plan to use 3 x 150mm dia, 12mm thick MDF discs on a central spindle as a former to wrap this around. the nearest thing i have seen is thick acetate sheet (what would glue this to MDF?) but I cant find a large enough sheet locally - needs to be 500mm x 300mm at least and thats bigger than A3...

suggestions?