There are many types of plastics, and so far there are about 300 types of plastics put into production in the world. There are many classification methods for plastics, and there are two commonly used ones:
1. According to the different properties of plastics after heating, they are divided into thermoplastic and thermosetting plastics:
The molecular structure of thermoplastic is linear, which softens or melts when heated, and can be molded into a certain shape. After cooling, it becomes hard again. After being heated to a certain extent, it softens again, and after cooling, it hardens again. This process can be repeated multiple times. Such as polyvinyl chloride, polyethylene, polystyrene, etc. The molding process of thermoplastic is relatively simple, capable of continuous production, and has a relatively high mechanical strength, so it has developed rapidly.
The molecular structure of thermosetting plastics is a bulk structure, which also softens when heated and can be molded into a certain shape. However, when heated to a certain degree or with the addition of a small amount of curing agent, it hardens and sets, and will not soften or change shape again when heated. Thermosetting plastics, such as phenolic plastics, amino plastics, epoxy resins, etc., cannot be recycled or reused as they no longer soften when heated after processing. The molding process of thermosetting plastics is relatively complex, so continuous production is somewhat difficult. However, it has good heat resistance, is not easily deformed, and is relatively inexpensive.
2. According to their different uses, plastics are divided into general plastics and engineering plastics:
General plastics refer to plastics with high production volume, low price, and wide application range, mainly including polyolefin, polyvinyl chloride, polystyrene, phenolic plastics, and amino plastics. Many products used in people's daily lives are made of these universal plastics.
Engineering plastics are plastics that can be used as engineering structural materials and as substitutes for metal manufacturing of machine components. 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 molding. They are widely used in industries such as automobiles, electrical appliances, chemicals, machinery, instruments, and meters, as well as in space navigation, rockets, missiles, and other fields.
There are many types of plastic packaging containers (such as plastic bottles), 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 molding, extrusion molding, compression molding, thermoforming, rotary molding, winding molding containers, etc.
(3) Plastic containers can be divided into box type, bottle type, bag type, hose type, etc. according to their shape and purpose.
