| 摘要 |
FIELD: polymer materials. ^ SUBSTANCE: invention relates to systems of tubes manufactured from polypropylene compositions. Tube according to invention has at least one layer made from propylene polymer characterized by melt flow rate value equal to or less than 2 g/10 min as measured in accordance with ASTM D1238, condition 1, said propylene polymer being selected from crystalline random propylene copolymer including 1 to 15 wt % C4-C10-alpha-olefin and crystalline random propylene copolymer including 1-15 wt % C4-C10-alpha-olefin and 1-7 wt % ethylene, both prepared via polymerization of monomers in one or more consecutive steps, or by combining products of two or more independent polymerization steps, wherein each polymer product from each step contains at least 2% of comonomer(s) units provided that at least one of the layers made from above-indicated propylene polymer is free of random propylene copolymers with 15% or less of ethylene as a only comonomer. Another object of invention is a method of manufacturing such tubes, which are characterized by improved performance characteristics regarding bursting internal pressure: creeping resistance, good balance of other mechanical properties, namely high rigidity and resistance to impact loads. ^ EFFECT: improved performance characteristics of tubes. ^ 5 cl, 5 dwg, 3 tbl, 4 ex |
