| 摘要 |
In a method of forming a shaped article (12) of a cross-linked polyolefinic material by forming a mixture of a thermoplastic olefinic material capable of forming a free radical with a crosslinking agent therefor, working the material under pressure in a shaping and crosslinking apparatus to produce uniform temperature rise within the mixture to a temperature at which the material can be extruded but at which substantial cross-linking does not occur, and thereafter shaping the material and initiating the cross-linking reaction and allowing the cross-linking reaction to proceed substantially to completion, the invention provides the improvement of subjecting the cross-linked material on leaving said apparatus to a high voltage of at least 1000 volts at a temperature greater than 100 DEG C. to detect non-activated free valencies thereby providing an indication of the degree of crosslinking. The invention also provides an apparatus (17) including means for heating a cross-linked polyolefinic material to a temperature in excess of 100 DEG C. means for applying a voltage above 1000 volts across said material, and means (23) for indicating any discharge occuring across said material. |
