Resistivity variance reduction

Abstract

Abstract IN THE HEAT TREATMENT OF CONDUCTIVE CARBON BLACKCONTAINING SELF-TEMPERATURE REGULATING ARTICLES SUCH AS RESISTIVE HEATERS TO REDUCE THEIR AS-FORMED RESISTIVITY TO A VALUE WITHIN THE RANGE FROM 5 TO ABOUT 100,000 OHM-CM., DEPENDENCE OF RESISTIVITY ON THERMAL HISTORY IS REDUCED RESISTIVITY VARIANCE FROM POINT ALONG THE ARTICLE IS DIMINISHED, AND RESISTIVITY OF THE ARTICLE FOR A GIVEN CONTENT OF CARBON BLACK IS REDUCED BY EXPOSING THE ARTICLE TO SUCCESSIVE THERMAL CYCLES IN EACH OF WHICH THE ARTICLE IS BROUGHT FROM A FIRST TEMPERATURE LESS THAN THE MELTING TEMPERATURE OF A CRYSTALLINE POLYMERIC MATRIX IN WHICH THE CARBON BLACK IS DISPERSED TO A SECOND TEMPERATURE AT OR ABOVE THE SAME, WHEREAFTER THE ARTICLE IS PERMITTED TO COOL BELOW THAT CRYSTALLINE MELTING TEMPERATURE. IN THE PREFERRED EXTRUDED FORM WHERE THE CRYSTALLINE POLYMERIC MATRIX IS COMPRISED OF BLENDED POLYETHYLENE AND ETHYLENE-ETHYL ACRYLATE COPOLYMER AND CONTAINS NOT MORE THAN ABOUT 15% BY WEIGHT CARBON BLACK, THERMAL CYCLING IS PREFERABLY CALCULATED TO ACHIEVE TOTAL EXPOSURE ON THE ORDER OF 24 HOURS TO OVEN TEMPERATURES OF ABOUT 300* F. OVER ABOUT 5-9 THERMAL CYCLES.

Inventors

• 👤 A Kampe

Bibliographic Details