| 摘要 |
<p>A method of extruding tubes etc. from a mixt. of PTFE and lubricant ("paste extrusion") utilises a piston-type extruder with an extrusion die or nozzle and a central mandrel. During extrusion, at least the end portion of the nozzle is rotated. The mandrel is pref. rotated simultaneously in the opposite direction. The nozzle or a part of it is pref. heated to a temp. exceeding, esp. by 50 degrees C, that of the mixt. in the cylinder. Used for PTFE pipes subsequently dried and sintered after extrusion. The rotational shearing action produces a circumferential fibrous structure superimposed upon the longitudinal fibrous structure, this imparting two-dimensional strength to the material.</p> |
