Main classification of PVC
PVC can be divided into soft PVC and hard PVC. Hard PVC accounts for about 2/3 of the market, and soft PVC accounts for 1/3. Soft PVC is generally used for the surface of floors, ceilings and leather, but because soft PVC contains softener (this is also the difference between soft PVC and hard PVC), it is easy to become brittle and difficult to store, so its scope of use has been limited. Hard PVC does not contain softener, so it has good flexibility, easy to form, is not brittle, non-toxic and non-polluting, and has a long storage time, so it has great development and application value. The essence of PVC is a vacuum plastic film, which is used for surface packaging of various types of panels. Therefore, it is also called decorative film and adhesive film, and is used in many industries such as building materials, packaging, medicine and so on. The building materials industry accounts for the largest proportion, at 60%, followed by the packaging industry, as well as several other small-scale applications.
The polyvinyl chloride molecule contains a chlorine atom. Due to the dipole effect of the C-CL bond, it is a very polar material. PVC has good acid and alkali resistance, wear resistance, flame resistance and insulation properties, but it has poor light and heat stability. Commercially, there are four methods for preparing PVC: suspension, bulk, emulsion, and solution. The suspension method is the most common, and most of the PVC resins used are such resins. Its products are classified into hard, semi-rigid and soft materials according to the plasticizer content (usually dibutyl phthalate or dioctyl phthalate). Rigid PVC contains 10-25% plasticizer, 30-40% semi-rigid PVC, and 40-70% soft PVC. All PVC products must contain a certain amount of stabilizer to avoid degradation during processing. Plasticizers in soft PVC products consist in softening the polymer. The choice of plasticizer or the mixing of plasticizers is ultimately determined by the desired properties of the finished product. Most plasticizers also function as processing aids to some extent. The plasticizer lowers the melting temperature and viscosity of the resin, thereby preventing the resin from sticking to the metal parts of the processing equipment.