Standard plastics, also called commodity plastics, are relatively inexpensive and are good for noncritical applications that don’t require outstanding thermal or mechanical properties.
Engineering plastics have better thermal or mechanical properties and are generally suitable for bearing-and-wear applications.
Advanced engineering plastics, also called high-performance plastics, have even better thermal or mechanical properties and are suitable for more demanding applications. Imidized plastics such as PAI offer the best performance.
The plastics on the left side of the pyramid are amorphous polymers, while those on the right side are semi-crystalline polymers. This distinction is based on whether the molecules that make up the plastic are arranged in a more random or in a more orderly way. The chart below summarizes the general properties of amorphous and semi-crystalline plastics.
Key Characteristics of Amorphous vs. Semi-Crystalline Plastics