Materials are awarded in a sliding scale. 3 materials are awarded for your first play of a mission, 2 materials for your second, and 1 material for your third. You will receive no materials for any plays beyond that, however you can collect supplies.
Materials are awarded for story missions only (Seasons 1 - 4). Materials are not given in the other missions types as these take place outside of the main storyline, and are designed to be replayable.