I believe that StarBoard is HDPE (high density polyethylene). ABS is acrylonitrile butadiene styrene. There are some differences in their properties, but I'm not sure that it would make any difference for our applications. I think ABS is lighter and stiffer, but maybe a little more brittle. HDPE might be more heat resistant? Oh, and StarBoard is smooth on both sides, while ABS sheets
always seem to come with a matte texture on one side, which I assume is supposed to be the "good" side. The smooth side scratches easily.
But really, I only started using it because I can get it for practically free. I went looking for StarBoard for a project
- "Wow, that's $120." "Oh, look, this stuff is $2.50!" Probably the plastics shop has scraps of HDPE too, sometimes, they just didn't on that day.
It's easy to make waterproof 3-dimensional stuff with ABS using the black pipe glue from the hardware
store. But you can heat-weld HDPE with the little plastic welding kit from Harbor Freight, which is fun too. ABS filament is also used in 3-D printers. Pretty soon we'll all be trading digital files for these little projects and just printing them out at home!
For an off-topic example, here's a little knock-off of the now-discontinued AquaSignal rail mount that I made from ABS one evening. Easy. And cheap
enough to throw away painlessly if something goes wrong.