Method of enhancing surface electrical conductivity of conductive plastics and conductive plastic films produced thereby
A method of enhancing surface electrical conductivity of an article formed of a conductive polymer material, such as a conductive polymer film, includes the step of providing an article formed of a conductive polymer. The conductive polymer is made up of a dielectric polymeric material and conductive fibers. A desired pressure is applied to at least a portion of the article while simultaneously heating at least a portion of the article to a desired temperature. The desired pressure and the desired temperature are maintained on at least a portion of the article for a desired time period. This method reduces a polymer-rich skin layer on the surface of the conductive polymer material and helps to randomize the orientation of the conductive fibers on the surface.
1. A method of enhancing surface electrical conductivity of an article formed of a conductive polymer material, comprising the steps of:
extruding an article formed of the conductive polymer material comprising a dielectric polymeric material and 10% to 14% conductive fibers by volume of the conductive polymer material, wherein a polymer-rich skin layer on a surface of the article has a concentration of conductive fibers in the skin layer that is less than 10% by volume of the skin layer and wherein at least 60% of the conductive fibers in the skin layer are oriented along the direction of extrusion;
applying a desired pressure to at least a portion of the article while simultaneously heating the at least a portion of the article to a desired temperature; and
maintaining the desired pressure and the desired temperature on the at least a portion of the article for a desired time period;
increasing the concentration of the conductive fibers in the skin layer to above 10% by volume; and
reorienting the conductive fibers in the skin layer such that less than 50% of the conductive fibers in the skin layer are oriented along the direction of extrusion.
2. The method according to claim 1 , wherein the desired pressure is about 27,580 kilopascals.
3. The method according to claim 1 , wherein the desired temperature is in a range from about 163° C. to about 190° C.
4. The method according to claim 1 , wherein the desired time period is about 10 minutes.
5. The method according to claim 1 , wherein the dielectric polymeric material is polyamide and the conductive fibers are nickel plated carbon fibers.
6. A method of forming a conductive polymer film having enhanced surface electrical conductivity, comprising the steps of:
extruding a conductive polymer tape comprising a dielectric polymeric material and 10% to 14% conductive fibers by volume, wherein a polymer-rich skin layer on a surface of the conductive polymer tape has a concentration of conductive fibers in the skin layer that is less than 10% by volume and wherein at least 60% of the conductive fibers in the skin layer are oriented along the direction of extrusion;
applying a desired pressure to the conductive polymer tape while simultaneously heating the conductive polymer tape to a desired temperature; and
maintaining the desired pressure and the desired temperature for a desired time period;
increasing the concentration of the conductive fibers in the skin layer to above 10% by volume; and
reorienting the conductive fibers in the skin layer such that less than 50% of the conductive fibers in the skin layer are oriented along the direction of extrusion.
7. The method according to claim 6 , wherein the desired pressure is about 27,580 kilopascals.
8. The method according to claim 6 , wherein the desired temperature is in a range from about 163° C. to about 190° C.
9. The method according to claim 6 , wherein the desired time period is about 10 minutes.