PVC can be divided into soft PVC and hard PVC. Among them, hard PVC accounts for about 2/3 of the market, and soft PVC accounts for 1/3. Soft PVC is generally used for floors, ceilings and the surface of leather. However, because soft PVC contains softeners (this is also the difference between soft PVC and hard PVC), it easily becomes brittle and difficult to preserve, so its range of use is limited. Hard PVC does not contain softeners, so it has good flexibility, is easy to shape, 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-absorbing film, which is used for the surface packaging of various types of panels, so it is also called decorative film and adhesive film. It is used in many industries such as building materials, packaging, medicine, etc. Among them, the building materials industry accounts for the largest proportion, 60%, followed by the packaging industry, and several other small-scale application industries.
Polyvinyl chloride molecules contain chlorine atoms. 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 has poor light and thermal stability. Commercially, there are four methods for preparing PVC: suspension method, bulk method, emulsion method and solution method. The suspension method is the most common, and the PVC resin used in most applications is this type of resin. Its products are divided into three types of materials: hard, semi-hard, and soft according to the amount of plasticizer they contain (generally dibutyl phthalate, dioctyl phthalate). Rigid PVC contains 10-25% plasticizer, semi-rigid PVC contains 30-40%, and soft PVC contains 40-70%. All PVC products must contain a certain amount of stabilizers to avoid degradation during processing. Plasticizers in soft PVC products serve to soften the polymer. The choice of plasticizer or blend of plasticizers is ultimately determined by the desired properties of the finished product. Most plasticizers also function as processing aids to some extent. Plasticizers reduce the resin's melting temperature and viscosity, thereby preventing the resin from sticking to metal parts of processing equipment.