I took a materials class 6 months before this interview. The manager asked me what classes I had taken in the past year, so I mentioned a few, including the materials. He then asked me to list common plastics (Polypropylene, Polystyrene, poly carbonate, polyethylene) ..... after somehow pulling them out of the back of my head, he asked me to differentiate each one and give examples where they are used (milk containers, shopping bags, protective eye wear). My advice, you NEVER know what you might be asked so stay on top of your game!