| 摘要 |
<p>The wall thickness of this kind of pipes is very small and, consequently, the impact strength is poor. The impact strength of pipes made of polyvinyl chloride can be improved by adding an admixture to the raw material, which, however, increases costs. According to the invention the impact strength can be improved by a ring-shaped elevation (4) formed at the foot of the ribs (3) on both sides thereof, which elevation joins the side wall of the rib over a sharp transitional juncture (5).</p> |
