PS (polystyrene or styrofoam) :- One of the most important thermoplastic materials, it is transparent, hard and inflammable, very bright and inert against many corrosive agents. It can be given shiny or opaque colors. Polystyrene is commonly used to replace glass, aluminum and wood because it is cheaper. It can also be used in packaging materials (including for foods), containers, boxes, lamps, disposable objects, cups and toys.