Classification of plastics

Classification of plastics:

1. According to the different components, plastics can be divided into simple component plastics and complex component plastics. (1) Simple component plastics: only a small amount of colorants, lubricants and other additives are added to the synthetic resin, such as polymethyl methacrylate (plexiglass), polystyrene, etc., or only a single synthetic resin, such as polytetrafluoroethylene.

(2) Complex component plastics: In addition to synthetic resins, several additives are added to change the properties of plastics, such as fillers, plasticizers, stabilizers, curing agents, etc.

2. According to the thermal characteristics, plastics can be divided into thermoplastics and thermosetting plastics.

(1) Thermoplastics: refers to plastics that can be repeatedly heated to soften and melt, and cooled to harden and set within a specific temperature range. The resin molecules of this type of plastic are often linear or branched structures, and generally only physical changes but no chemical changes occur during the molding process. Commonly used thermoplastics include polyethylene, polyvinyl chloride, polystyrene, polypropylene, ABS, polyamide, polyoxymethylene, polycarbonate, polyphenylene ether, polysulfone, chlorinated polyether, polymethyl methacrylate and fluoroplastics.

 (2) Thermosetting plastics: refers to plastics that can soften and melt when heated to a certain temperature for the first time, can be molded into shape, and harden and set after further heating or adding curing agent. The resin molecules of this type of plastic are also linear structures at first. During the molding process, due to heat or the action of curing agent, chemical bonds are generated between the molecular chains, that is, cross-linking reactions occur, and the molecular structure gradually transforms into a network structure and finally into a three-dimensional structure. Thermosetting plastics undergo both physical and chemical changes during the molding process. After molding, they will not soften and melt again when heated again. Commonly used thermosetting plastics include phenolic plastics, epoxy resins, amino plastics, silicone plastics, etc.