| 摘要 |
Increasing the tensile strength of packing strips is by a drawing process in which the strip is manufactured from at least two superimposed layers, preferably bonded together; these two layers may be the walls of a flattened tube or may be parallel strips. A blank of the strip is extruded in the form of a gauged tube and is, after cooling, re-heated, pre-drawn, heated again and subjected to the principal drawing; in this process a heated mandrel brings the internal face of the tube to the melting point temperature and this is welded flat between rollers into a flat strip. The latter is then subjected to a final drawing, thermostabilised, cooled, and finally irradiated by high energy radiation to effect cross-linking. The shaping of the surfaces of the strips is by means of rollers; these surfaces may be grooved longitudinally or they may be given a zig-zag form, preferably with rounded hollows. |
