| 摘要 |
A method is achieved to treat polytetrafluoroethylene-based items, especially machine parts such as doctor blades, sealings, bearing bushes and the like, so that the thermal expansion (and retraction) of the items at least in the most critical dimensioning direction becomes essentially smaller after the treatment as compared with the expansion of a non-treated item. The essential steps of the method are: the item is heated to its operating temperature, or slightly above, allowing it to expand in a free manner corresponding to the increase in the temperature; heating is ceased; the item is fastened so that changes in its dimensions, at least those in the direction of dimensioning, are prevented; and the item, still fastened in the said manner, is allowed to cool down to tile surrounding temperature and kept fastened for at least 12 hours; the item is unfastened and the amount of retraction in the direction of dimensioning is measured and the dimensions of the item are determined, taking the retraction into consideration. |
