From The Collaborative International Dictionary of English v.0.48:

noninterchangeable \noninterchangeable\ adj.
   1. (math, logic) not able to be interchanged without changing
      the truth value.
      [WordNet 1.5]

   2. Not able to be substituted for each other; -- of objects,
      such as parts of machinery; as, the ink cartidges on the
      new printer are noninterchangeable with those on the older
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