Classification of Engineering Plastics

By Purpose

General Plastics:Commonly referred to as general plastics, these are large in production, low in cost, versatile, and widely used. Examples include polyethylene, polypropylene, polyvinyl chloride, polystyrene, ABS (acrylonitrile-butadiene-styrene), polymethyl methacrylate, and amino plastics. They constitute over 90% of the total plastic production, earning them the name “bulk plastics.”
Engineering Plastics: These plastics serve as engineering materials and can replace metal in manufacturing machine components. Engineering plastics exhibit excellent comprehensive performance, high rigidity, low creep, high mechanical strength, good heat resistance, good electrical insulation, and can be used long-term in demanding chemical and physical environments. They can substitute for metals as structural materials in engineering. However, they are more expensive and have a smaller production volume. Engineering plastics can be further divided into general engineering plastics and special engineering plastics. Examples of general engineering plastics include polyamide, polycarbonate, polyoxymethylene, modified polyphenylene ether, and thermoplastic polyester. Special engineering plastics include heat-resistant plastics with a temperature resistance above 150°C, such as polyimide, polysulfide, polyarylate, aromatic polyamide, polyarylester, polyphenylene ester, polyaryletherketone, liquid crystal polymers, and fluororesins.

By Thermal Forming Processing Performance

Thermosetting Plastics:These plastics soften and flow during the first heating, undergo a chemical reaction to crosslink and solidify at a certain temperature, and this change is irreversible. They cannot soften and flow again upon reheating. Examples include phenolic, urea-formaldehyde, melamine-formaldehyde, epoxy, unsaturated polyester, and organosilicon plastics. Thermosetting plastics form a three-dimensional network structure after resin curing, making them unable to melt or dissolve in solvents. They are commonly used in applications requiring heat insulation, wear resistance, insulation, and high-voltage electrical properties.
Thermoplastic Plastics:These plastics soften and flow when heated, solidify when cooled, and this process is reversible. Examples include polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyacetal, polyethylene terephthalate, and polyamides. Thermoplastic plastics have linear or branched molecular structures, and there are no chemical bonds formed between molecular chains during the molding process. They soften upon heating and solidify upon cooling, undergoing a physical change.

By Transparency

Transparent Plastics:Plastics with a light transmittance of over 88% are classified as transparent plastics. Examples include polymethyl methacrylate (PMMA), polystyrene (PS), polycarbonate (PC), and Z-polyester.
Translucent Plastics:Examples include polypropylene (PP), polyvinyl chloride (PVC), polyethylene (PE), acrylonitrile-styrene (AS), polyethylene terephthalate (PET), methyl methacrylate-butadiene-styrene (MBS), and polystyrene film (PSF).
Opaque Plastics:Mainly include polyoxymethylene (POM), polyamide (PA), ABS, high-impact polystyrene (HIPS), and polyphenylene oxide (PPO).

By Hardness

Hard Plastics:Examples include ABS, POM, PS, PMMA, PC, PET, PBT, and PPO.
Semi-Hard Plastics:Examples include PP, PE, PA, and PVC.
Soft Plastics:Examples include soft PVC, thermoplastic elastomers (TPE), thermoplastic rubber (TPR), ethylene-vinyl acetate (EVA), and thermoplastic polyurethane (TPU).

By Chemical Structure