| 摘要 |
A pipe of layers of thermoplastic polyolefins of the same type, however with different properties, which are connected inseparably with one another, an outer first layer and a second layer, adjoining the first layer on the inside, consisting of a material, which has not been cross-linked, the second layer approximately having the FNCT the value or the NPT value of a one-layer standard pressure pipe and the first layer having an FNCT or NPT value, which is higher by a factor of at least 3 than that of the second value. Moreover, a third layer is provided, which adjoins the second layer on the inside, also consists of material that is not cross-linked and has a PNCT, which is higher by a factor of at least 3 than that of the second layer and an NPT layer, which is higher by a factor of at least 2 than that of the second layer.
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