POM is a crystalline plastic often used for technical applications due to its strength, ductility (ability to be drawn into threads without breaking) and good machinability. Its properties make it suitable for click connections (e.g. bicycle lamp holders). The material is known for its stiffness, strength and hardness up to 120ºC, and is as elastic as many metals. It is wear resistant and has a very low friction coefficient. The colour is opaque white, and carbon black can be added to protect the product from UV-light.
PBT is a semi-crystalline, white or off-white polyester similar in both composition and properties to polyethylene terephthalate (PET). It has slightly lower strength and stiffness than PET. PBT is softer, but it has higher impact strength and very similar chemical resistance. It is usually preferred for industrial scale moulding due to quicker crystallising. It is widely used in electronic, electrical, communications, fibre optics and automotive industries.
To find out more Engineering Plastics Methodology August 2012