:Aliphatic polyketones are a new family of engineering thermoplastics derived from carbon monoxide and ethylene or other alpha-olefins. These semi-crystalline polymers possess a unique balance of properties not found in other Engineering Thermoplastic Polymers (ETP's). They exhibit the desirable combination of toughness, stiffness, and thermal characteristics normally associated with amorphous polymers. In addition, they have low permeability and chemical resistance exceeding that of many other semi-crystalline polymers. Due to this unique combination of properties, fuel systems suppliers are evaluating these materials as candidates for addressing the evolving automotive industry requirements.