Tensile strength (plastic in tension) and compression strength (plastic under compression) are important values for structural applications. 

Good Choices: Peek, PPS, Nylon, Delrin 

Poor Choices: Teflon, UHMW, LDPE, HDPE, Polypropylene 

Consider either continuous service temperature in air or heat deflection temperature if under load. 

Good Choices: PTFE, PEEK, Torlon, PPS 

Poor Choices: Acrylic, UHMW, ABS, PVC 

A combination of pressure and velocity that determines whether a plastic material has enough thermal and structural ability to withstand a bearing application in rotational wear. 

Good Choices: Peek, Nylatron, Delrin AF, Torlon 4301 

Poor Choices: UHMW, PBT, PETG Nylon 

Machined plastics do not have the structural stability of metals. This is primarily caused by their tendency to absorb water and a high coefficient of thermal expansion. Stable materials have low water absorption with a low CTFE.  

Good Choices:Peek, PPS, PETG 

Poor Choices: Nylon, UHMW, HDPE, LDPE 

Chemical resistance of plastics is variable. Some materials show an almost universal resistance to chemicals while others are very sensitive and stress crack when exposed. Best practice is to consult a reference guide for a specific chemical/plastic interaction. 

Good Choices: Teflon, UHMW, CTFE, PEEK 

Poor Choices: Acrylic, ABS, Noryl, Polysulfone 

A measurement of a plastics ability to withstand a sudden shock or a blow. Do not confuse this with resistance to steady state stress where failure can occur from chemical attack or configuration stress risers. Polycarbonate can tolerate high impact but stress cracks from steady loading. 

Good Choices: Nylon, Polycarbonate, UHMW, Peek 

Poor Choices: PETG, Acrylic, Polyphenylene 

General measure of cost of the material. Higher performance engineered plastics are more expensive. 

Inexpensive Choices: Delrin, UHMW, Polypropylene, HDPE 

Expensive Choices: Peek, Vespel, PPS, Radel HDPE 

Suitability for use in medical device applications. Plastics carry the USP class VI designation. 

Good Choices: Polycarbonate, Peek, UHMW, Radel 

The Food and Drug administrations’ classification for plastics which contact food. 

Good Choices: Delrin, PETG, Polycarbonate (some grades, S&D are one of the few comapnies that stock food grade polycarbonate), Peek.

Resistance to UV typically seen in outdoor use. Plastics without resistance will age and become brittle. Because of the coloring, most black plastics have at least a small amount of resistance. 

Good Choices: Ultem, Polycarbonate (UV stabilized grade only, non FDA), PBT 

Poor Choices: Polycarbonate (FDA), Nylon, Acetal