PBT (Polybutylene terephthalate) is one of two basic forms of polyester materials available in machinable stock shapes today. PBT offers high impact resistance along with excellent resistance to typical cleaning chemicals chlorine and caustic solutions. PBT differs from PET in that PBT has a lower strength and stiffness but this in turn increases the impact resistance of PBT. PBT also has a lower glass transition temperature. Both however are susceptible to hot water or steam if operating above 140° F. Both PBT and PET retain more of their physical properties at elevated temperature when compared to Acetal and Nylon. Internal lubricants can be added to enhance the wear resistance and coefficient of friction when compared to unfilled versions or Delrin AF. PBT has good electrical insulation properties and has good dimensional stability. PBT is approved for direct food contact by the FDA and is an ideal material for food processing equipment.