| 摘要 |
<p>A molecularly-oriented two-part extrusion is made by extruding a second part (7) into thermal and mechanical engagement with a first part (3) already extruded, cooled and advanced at a speed restricted by a gripping device (5). The product is taken up at a higher speed, to effect elongation. At least one of the parts is of a crystallisable polymeric material, and elongation takes place at a point between the extruder (6) and the take-up where, as a result of cooling of the second part and or the concurrent heating of the first, it is at a temperature between its glass transistion temperature between its crystalline melting point. Both parts may be of crystallisable polymeric material and at such a temperature when elongation takes place. They may be inner and outer layers drawn down during elongation onto a wire or other core.</p> |
