Resin casting question..

[Shahram]

Hi all,

I am not sure if this question is very related to this forum or not,
but this is the closest group I have found in my google search. So
here is my problem and questions:

I have two components one made of metal and the other from a type of
polyethylene, which I would like to keep them fixed rigidly with
respect to each other at a particular position while I am taking x-
rays of them from different angles. To solve this problem, I have
thought of using a an expanding rigid foam (similar to insulation
spray foams) or a form of fast curing resin that can sourround the
components and the space between them like a mold and hold them
rigidly with repect to each other. If the denisty of the foam is less
than my polyethylene component, I would still be able to successfully
visualize the component under x-ray. I want to be able to seperate the
components from the resin/foam after I am done with the work because
they are expensive and I don't want to ruin them. I don't want the
expansion of the foam to push the components away from where they are
initially. I can only weakly secure the locations of the components
using some additional side rods and plasticine. Do you suggest any
particular resin or foam? Any particular protecting material for the
surface of the components? Any particular method for casting them?
Have you seen any similar application I can look into?

Thanks,
Shahram