While thermosets can be extruded by heating them, the majority of extruded plastics are thermoplastics. Within that classification there is a wide range of high performance, engineering grade, and commodity plastics to choose from, all of which can include amorphous or crystalline molecular structures.
High performance plastics are the rarest and most expensive types to be extruded; these plastics are made for harsh environments and feature especially good thermal and mechanical properties. One such plastic is polyetherketone (PEK), which is used in the aerospace and automotive industries because it’s resistant to chemicals, flame, and shrinkage, as well as being remaining strong over a range of temperatures.
One step below are engineering plastics, which are specialty plastics designed to include unique properties without being as expensive as high performance materials. These include TPE, ABS, nylon, and polycarbonate. Finally, commodity plastics are more general use materials that make up the majority of extrusions. These plastics, which include polypropylene, polyethylene, and PVC, are the least expensive plastic types.
Finally, any plastic from these three groups can either have amorphous or crystalline polymer structure, which lends certain properties. Amorphous structures, such as those found in PVC, ABS, and polycarbonate, have messy, mobile polymer chains. This lends them flexibility, elasticity, and impact and shrinkage resistance. However, they’re not as strong or chemically resistant as crystalline structure plastics, like HDPE or polypropylene. These plastics have rigid structures that lend heat resistance, strength, and stiffness. However, they also tend toward shrinkage and don’t have much impact resistance.
Read more: Types of Plastic Extrusion Materials