| 摘要 |
<p>Stage 1 comprises quenching continuously extruded and calibrated tubing to an optimum crystallisation temperature (approx. 100-120 degrees C. for polypropylene) and promptly reheating sufficiently (160 degrees C for polypropylene) while passing through a successive bath to be longitudinally oriented in sections by a travelling rack which reciprocates sufficiently quickly to match the overall output rate of the extruder. The hot drawn pipe is pinched at intervals of parison length and cooled sufficiently to prevent retraction when subsequently released and cut into segments. Stage 2 comprises holding parison segments in 'C' clamps with the open end uppermost, passing through a hot bath and then through a moulding station where the softened parison is moulded by pneumatic pressure on the open end.</p> |
