The sheet for blister packaging is called hard sheet or film. Commonly used are: PET (polyethylene terephthalate) hard sheet, PVC (polyvinyl chloride) hard sheet, PS (polystyrene) hard sheet. PS hard sheet has low density, poor toughness, and is easy to burn. It produces styrene gas (hazardous gas) when burned, so it is generally used to produce various industrial plastic trays. PVC hard sheet has moderate toughness, is not easy to burn, generates chlorine gas when burned, and has certain influence on the environment. PVC is easy to heat seal, and can be sealed by sealing machine and high frequency machine. It is the main raw material for producing transparent plastic products. PET hard sheet has good toughness, high transparency, easy to burn, no harmful gas when burning, and is an environmentally friendly material, but the price is high, suitable for high-grade plastic products. The blister bulbs in Europe and the United States generally require PET hard sheets, but It is not easy to heat seal, which brings great difficulties to the packaging. In order to solve this problem, a material called PETG ethylene glycol modified-polyethylene terephthalate is used, which is easy for PVC. Heat sealing, but also PET's high environmental protection and transparency, but the price is higher.