EPS foam is an excellent packaging material, such as TV sets, refrigerators, washing machines, air conditioners, electronic instruments, precision instruments, glassware, ceramic products, handicrafts and other products, which can not be separated from EPS foam as a cushioning packaging material. EPS foam plastic is a light material which is based on polystyrene resin, added with auxiliary materials such as foaming agent, and heated and foamed. With the advantages of light weight, low thermal conductivity, low water absorption, water resistance, aging resistance, low temperature resistance, easy processing, low price and high quality, it is an indispensable heat preservation material container for seafood freezing, vegetable preservation, incubators, cold storage, refrigerated trucks, railway passenger cars and so on. EPS packaging is easy to recycle and is a good green packaging material. Before use, just put the ice bag in the refrigerator into the household refrigerator for full freezing, and then put the ice bag into the passive car refrigerator for refrigeration, which is very convenient to use and can generally keep the low temperature for more than 72 hours. In winter, if the ice pack is fully heated in the microwave oven and put into the passive car refrigerator, it can also play a role in heat preservation. This kind of passive refrigerator not only avoids the noise generated when the compressor works, but also has the characteristics of energy saving, environmental protection, no noise, portability and flexibility of semiconductor refrigerators, and is expected to occupy a place in the car refrigerator market.