There are many types of synthetic resins.
Synthetic resin industrial products can be divided into general-purpose resins and special-purpose resins. General-purpose resins have large output and low cost. They are generally used in general consumer goods or durable goods. Representative varieties are polyethylene, polypropylene, polyvinyl chloride, polystyrene and ABS. The resin produced has a small output and a high production cost. For example, it can replace metals in machinery, electronics, automobiles and other sectors. Engineering plastics belong to the category of special resins. Important engineering plastics include polyamide, polycarbonate, polyoxymethylene, polybutylene terephthalate, modified polyphenylene ether and polytetrafluoroethylene. Another type of special resin is thermoplastic elastomer, which has rubber-like elasticity and can be reshaped when heated.
According to chemical composition, synthetic resins can be roughly divided into two categories: one kind of main chain is composed of aliphatic carbon atoms, general-purpose resins basically belong to this category; the other kind of synthetic resins also contain carbon atoms in the main chain Most engineering plastics, such as oxygen, nitrogen and sulfur, are composed of hetero-chain polymers.
According to engineering performance, synthetic resins can be divided into thermoplastic resins and thermosetting resins. The difference mainly comes from the chemical composition and molecular structure of the polymer. The molecular chain structure of thermoplastic resin is linear or branched, which can be plasticized (or softened, melted) and flowed after being heated, and can be repeatedly plasticized and formed. Typical thermoplastic resins are polyethylene, polypropylene, poly-1-butene, polyvinyl chloride, polystyrene and the like. Thermoplastic resins can be quickly molded and reshaped. Thermosetting resin is a high molecular polymer with a three-dimensional structure. It contains multifunctional macromolecules in the molecular chain. It can be softened (or melted) and solidified (or matured) at the same time to become insoluble, Infusible polymer. Commonly used typical thermosetting resins are phenol-formaldehyde resin (commonly known as phenolic resin), urea-formaldehyde resin (commonly known as urea-formaldehyde resin), melamine-formaldehyde resin (commonly known as melamine-formaldehyde resin), epoxy resin, unsaturated polyester resin, polyurethane and so on.
