Long fiber thermoplastic process for conductive composites and composites formed thereby

Abstract

The present invention relates to a polymer article that includes electrically conductive fibers to provide electrical electromagnetic interference (EMI) shielding and their method of manufacture. The invention includes a method for forming shielding materials by impregnating conductive fibers in a polymer material via direct injection of the conductive fibers into the extrusion process. The invention also includes EMI shielding polymers and products that are radio-frequency and electromagnetically shielded by parts formed of the shielding polymer.

1 . A fiber reinforced polymer article having improved electromagnetic shielding properties, comprising: 
 a thermoplastic polymer; and    less than 10 percent by weight conducting fibers wherein the composite article has an electromagnetic shielding efficiency of at least 70 dB.    
     
     
         2 . The fiber reinforce polymer article of  claim 1 , wherein the electromagnetic shielding efficiency is least 90 dB.  
     
     
         3 . The fiber reinforce polymer article of  claim 1 , wherein said conducting fibers are present in an amount less than 5 percent by weight  
     
     
         4 . The fiber reinforce polymer article of  claim 1 , wherein said thermoplastic is selected from the group consisting of acrylonitrile-butadiene-styrene (ABS), polyethylene terephthalate (PET), polybutylene terephthalate (PBT) and polyethylene (PA).  
     
     
         5 . The fiber reinforce polymer article of  claim 1 , wherein property deterioration of said thermoplastic due to melt history is substantially reduced  
     
     
         6 . A method of manufacturing a composite article including the steps of: 
 melting a thermoplastic material;    adding conductive fibers to said melted thermoplastic material;    cutting said conducting fibers to a predetermined length; and    injection molding the thermoplastic material to form a composite article having a electromagnetic shielding efficiency of at least 70 dB.    
     
     
         7 . A digital device having an electromagnet shield, said shield comprising: 
 a thermoplastic polymer; and    less than 10 percent by weight conducting fibers wherein the composite article has an electromagnetic shielding efficiency of at least 70 dB.    
     
     
         8 . The fiber reinforce polymer article of  claim 7 , wherein the electromagnetic shielding efficiency is least 90 dB.