There are many types of plastics, and there are about 300 kinds of plastics put into production in the world so far. There are many classification methods for plastics, and there are two commonly used ones:
1. According to the different properties of the plastic after being heated, it is divided into thermoplastic plastics and thermosetting plastics:
The molecular structure of thermoplastics is a linear structure, which softens or melts when heated, can be molded into a certain shape, and then becomes hard after cooling. It softens again after being heated to a certain extent, and then hardens after cooling. This process can be repeated many times. Such as polyvinyl chloride, polyethylene, polystyrene, etc. The molding process of thermoplastics is relatively simple, can be produced continuously, and has relatively high mechanical strength, so it develops rapidly.
The molecular structure of thermosetting plastics is a body structure, which also softens when heated, and can be molded into a certain shape, but after heating to a certain degree or adding a small amount of curing agent, it will be hardened and set, and it will not become soft or change after heating. Shape now. After being processed and formed, thermosetting plastics will no longer be softened by heat, so they cannot be recycled and reused. For example, phenolic plastics, amino plastics, and epoxy resins all belong to this type of plastic. The molding process of thermosetting plastics is relatively complicated, so there are certain difficulties in continuous production, but its heat resistance is good, it is not easy to deform, and the price is relatively low.
2. According to different uses of plastics, it is divided into general plastics and engineering plastics:
General-purpose plastics refer to plastics with large output, low price and a wide range of applications, mainly including polyolefin, polyvinyl chloride, polystyrene, phenolic plastics and amino plastics. Many products used in people's daily life are made of these general-purpose plastics.
Engineering plastics are plastics that can be used as engineering structural materials and replacing metal manufacturing machine parts. For example, polyamide, polycarbonate, polyoxymethylene, ABS resin, polytetrafluoroethylene, polyester, polysulfone, polyimide, etc. Engineering plastics have the characteristics of low density, high chemical stability, good mechanical properties, superior electrical insulation, and easy processing and forming. They are widely used in industries such as automobiles, electrical appliances, chemicals, machinery, instruments, meters, etc., and are also used in space navigation and rockets. , Missiles and other aspects.
There are many types of plastic packaging containers (plastic bottles, etc.), which can usually be classified according to the following methods:
(1) According to chemical composition: plastic containers can be divided into PE, PP, PS, PVC, PET, NY, PC, PF, UF containers, etc.
(2) According to the molding method: plastic containers can be divided into blow molding, injection, extrusion, molding, thermoforming, rotating, and winding molding containers.
(3) According to the shape and purpose of the container, plastic containers can be divided into boxes, bottles and cans, bags, hoses and so on.