Corrugated multi-layer tubing having at least one fluoroplastic layer

A multi-layer tube suitable for use on motor vehicles comprising a cylindrical wall having an outer surface, and an inner surface essentially parallel to the outer surface, the inner surface defining an essentially cylindrical interior, said essentially cylindrical interior extending longitudinally through the tube coaxial to a longitudinal axis, the cylindrical wall itself comprising:

• a first region having an essentially uniform cross-sectional diameter in which the cylindrical wall has a flat in longitudinal cross-section, the cylindrical wall oriented essentially parallel to the coaxial longitudinal axis;
• and
• a second region in which the cylindrical wall has at least one convolution having a cross-sectional diameter which varies positionally depending on longitudinal location in the second region, the convolution having cross-sectional diameter different from the essential uniform cross-sectional diameter of the first region and has a maximum inner diameter which is between about 20% and about 300% greater than the essentially uniform cross-sectional inner diameter of the first region, the cylindrical wall of the multi-layer tubing further comprising:
• an outer tubing having an inner and an outer face, the outer tubing consisting essentially of an extrudable polyamide having an elongation value of at least 150% and an ability to withstand impacts of at least 2 ft/lbs at temperatures below about -20.degree. C.;
• an intermediate bonding layer having a thickness between about 0.05 mm and about 0.2 mm and an elongation value between about 150% and about 250%, the intermediate bonding layer bonded to the inner face of the thick outer layer, the bonding layer consisting essentially of an extrudable thermoplastic capable of sufficiently permanent laminar adhesion to the polyamide outer tubing and exhibiting at least some resistance to short-chain hydrocarbon molecules conveyed through the tubing;
• and
• an inner hydrocarbon barrier layer bonded to the intermediate bonding layer having a thickness between about 0.05 m and about 0.2 mm and an elongation value of at least 150%, the inner layer consisting essentially of an extrudable, melt process fluoroplastic capable of sufficiently permanent laminar adhesion with the intermediate bonding layer selected from the group consisting of polyvinylidine fluoride, polyvinyl fluoride, polychlorotrifluoroethylene, ethylene tetrafluoroethylene copolymers, and mixtures thereof.