Polystyrene (PS) plastic is a naturally transparent thermoplastic that is available as both a typical solid plastic as well in the form of a rigid foam material. PS plastic is commonly used in a variety of consumer product applications and is also particularly useful for commercial packaging.

Polystyrene (PS) for Prototype Development on CNC Machines and 3D Printers: Polystyrene is available in sheet stock, rod stock, and in various shapes. It is a great candidate for subtractive machining processes on a CNC machine. Colors are usually limited to clear, white, and black although colors can be added and it is an excellent candidate for external painting.

General Purpose Polystyrene (GPPS) and High Impact Polystyrene (HIPS) are probably the most commonly used PS resins for injection molding. GPPS is clear, but brittle (think of a CD jewel case) while HIPS is opaque and much less brittle.