PVC is polyvinyl chloride, and polyvinyl chloride is also a commonly used plastic. It is a resin composed of PVC resin, plasticizer and antioxidant, and it is not toxic in itself. However, the main auxiliary materials such as plasticizers and antioxidants are toxic. The plasticizers used in daily-use PVC plastics mainly include dibutyl terephthalate and dioctyl phthalate. These chemicals are toxic, and so is lead stearate, an antioxidant of PVC. When PVC products containing lead salt antioxidants come into contact with solvents such as ethanol and ether, lead will be precipitated. When PVC containing lead salt is used as food packaging, lead molecules will diffuse into oil when encountering fried dough sticks, fried cakes, fried fish, cooked meat products and cakes and snacks, so it is not possible to use PVC plastic bags to pack food, especially oily food.

In addition, PVC plastic products will slowly decompose hydrogen chloride gas at high temperature, such as about 50℃, which is harmful to human body, so PVC products are not suitable as food packaging materials. Bakelite (phenolic plastic) contains free phenol and formaldehyde, which is toxic to human body and not suitable for food storage and food packaging. Although electric jade (urea-formaldehyde plastic) is odorless and tasteless, it will release free formaldehyde in boiling water at 100℃ or when it is used to hold vinegar food, which is harmful to human body and is not suitable for tableware or food packaging. Newer products of waste plastics (some of which may add some new materials) are difficult to ensure non-toxicity because of their complex components, so they are generally not used as food containers and packaging materials.

Medical-grade polyvinyl chloride (PVC) or polycarbonate (PC) are mostly used in disposable medical devices. The thermal decomposition products in the processing of PVC have strong corrosiveness to steel, while PC has high hardness and viscosity, so the parts and components of plasticized parts must have high corrosion resistance, wear resistance and polishing performance. Most medical injection molding machines use hard chromium or stainless steel plating on the barrel screw as a material to manufacture a simple screw to meet the above special requirements. In addition, in order to prevent the gas generated by thermal decomposition during PVC processing, it is required to aluminize the surfaces of the movable template and the fixed template, and at the same time, aluminize the surrounding metal sheets or make metal sheets with stainless steel plates, and seal the flat seams of the metal sheets with non-toxic silica gel to prevent the gas generated during plastic processing from being emitted to the outside (the gas generated during plastic processing can be collected by special equipment, purified and discharged into the atmosphere).