Ice is darn handy stuff and is likely to be used in lots of ways, often in applications that allow it to 'multi-task' in various roles. If you've got to lug mass around space anyway, you might as well maximize the use of it.
Lots of ships will probably be designed so that the crew quarters are in the center while the fuel tanks and such are on the outside to provide additional shielding.
This is not to say that plastic won't have a role. Hydrocarbons in various forms are also darn useful in a nanotech equipped civ. Perhaps plastic might play a role in smaller craft or spacesuits or devices that don't readily allow for lots of ice based shielding.
Todd
Lots of ships will probably be designed so that the crew quarters are in the center while the fuel tanks and such are on the outside to provide additional shielding.
This is not to say that plastic won't have a role. Hydrocarbons in various forms are also darn useful in a nanotech equipped civ. Perhaps plastic might play a role in smaller craft or spacesuits or devices that don't readily allow for lots of ice based shielding.
Todd