Conductive plastic compositions and method of manufacture thereof

Abstract

An improved, conductive, polymeric composition comprises a polymeric resin; an electrically conductive filler system comprising small carbon fibers and either carbon powder or fibrous non-conductive filler or a combination of both. The amount of the conductive filler system utilized is dependent upon the desired electrical conductivity (surface and volume conductivity or resistivity) while preferably preserving intrinsic properties of the polymeric resin such as impact, flex modulus, class A finish, and the like. The conductive articles made from these compositions can therefore be used for electromagnetic shielding, electrostatic dissipation or antistatic purposes in packaging, electronic components, housings for electronic components and automotive housings.

1 . An improved, conductive, polymeric composition comprises: 
 a polymeric resin; and    an electrically conductive filler system comprising vapor grown carbon fibers and either carbon powder, fibrous non-conductive filler, or a combination of carbon powders and fibrous non-conductive filler.    
     
     
         2 . The composition of  claim 1 , wherein the polymeric resin is a thermoplastic selected from the group consisting of polyacetal, polyacrylic, styrene acrylonitrile, acrylonitrile-butadiene-styrene, polycarbonate, polystyrene, polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, nylons, polyamideimide, polyarylates, polyurethane, ethylene propylene rubber, ethylene propylene diene monomer, polyarylsulfone, polyethersulfone, polyphenylene ether, polyphenylene sulfide, polyvinyl chloride, polysulfone, polyetherimide, polytetrafluoroethylene, fluorinated ethylene propylene, perfluoroalkoxy, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polyetherketone, polyether etherketone, polyether ketone ketone; and mixtures comprising at least one of the foregoing thermoplastic or a thermoset selected from the group consisting of polyurethanes, natural rubber, synthetic rubber, epoxy, phenolic, polyesters, polyamides, silicones; and mixtures comprising at least one of the foregoing thermosets.  
     
     
         3 . The composition of  claim 1 , wherein the polymeric resin comprises a blend of a thermoplastic resin with a thermoset.  
     
     
         4 . The composition of  claim 1 , wherein the polymeric resin comprises about 10 to about 99 wt % of the total composition.  
     
     
         5 . The composition of  claim 1 , wherein the vapor grown carbon fibers are selected from the group consisting of graphitic vapor grown carbon fibers, partially graphitic vapor grown carbon fibers, and mixtures comprising one of the foregoing vapor grown carbon fibers.  
     
     
         6 . The composition of  claim 1 , wherein the vapor grown carbon fiber comprises about 0.25 to about 30 wt % of the total composition.  
     
     
         7 . The composition of  claim 1 , wherein the vapor grown carbon fibers have diameters of about 0.3 to about 2000 nanometers and an aspect ratio of greater than about 5.  
     
     
         8 . The composition of  claim 1 , wherein the carbon powder comprises about 0.25 to about 25 wt % of the total composition.  
     
     
         9 . The composition of  claim 1 , wherein the carbon powder is carbon black.  
     
     
         10 . The composition of  claim 1 , wherein the fibrous non-conductive filler is selected from the group consisting of aluminum silicates, aluminum oxides, magnesium oxides, calcium sulfate hemihydrate, boron fibers, ceramic fibers, silicon carbide, basalt fibers, silicon carbide, alumina, boron carbide, glass, quartz, wood flour, cellulose, cotton, sisal, jute, hemp cloth, felt, starch, cork flour, lignin, ground nut shells, corn, rice grain husks, polyethylene terephthalate fibers, polyvinylalcohol fibers, aromatic polyamide fibers, polybenzimidazole fibers, polyimide fibers, polyphenylene sulfide fibers, polyether ether ketone fibers, polybenzoxazole fibers, polyester fibers, polyethylene fibers, polytetrafluoroethylene fibers, polyacrylic fibers, polyvinyl alcohol fibers, aramid fibers and mixtures comprising at least one of the foregoing fibrous non-conducting fillers.  
     
     
         11 . The composition of  claim 1 , wherein the fibrous non-conductive filler is glass fiber selected from the group consisting of E-glass, A-glass, C-glass, D-glass, R-glass, S-glass, and mixtures comprising at least one of the foregoing glass fibers and is present in an amount of up to about 50 wt % of the total composition  
     
     
         12 . The composition of  claim 1 , wherein the fibrous non-conductive filler comprises up to about 50 wt % of the total composition.  
     
     
         13 . A conductive composition comprising: 
 a thermosetting polymeric resin;    vapor grown carbon fibers;    carbon black; and    glass fibers.    
     
     
         14 . The composition of  claim 13 , wherein the thermosetting polymeric resin is selected from the group consisting of polyurethanes, natural rubber, synthetic rubber, epoxy, phenolic, polyesters, polyamides, silicones; and mixtures comprising at least one of the foregoing thermosetting resins.  
     
     
         15 . The composition of  claim 13 , wherein the vapor grown carbon fibers have a diameter of about 3.5 to about 2000 nm, an average aspect ratio greater than or equal to about 5, and comprise about 0.25 to about 30 wt % of the total composition.  
     
     
         16 . The composition of  claim 13 , wherein the carbon black comprises about 0.25 to about 25 wt % of the total composition.  
     
     
         17 . The composition of  claim 13 , wherein the glass fibers comprise about 0 to about 50 wt % of the total composition.  
     
     
         18 . A method of forming an extruded conductive pellet comprising: 
 melt blending a polymeric resin, vapor grown carbon fibers and carbon powder, glass fibers or a mixture of carbon powder and glass fibers;    extruding the blend; and    pelletizing the extrudate.    
     
     
         19 . The method of  claim 18 , wherein the polymeric resin is a thermoplastic selected from the group consisting of polyacetal, polyacrylic, styrene acrylonitrile, acrylonitrile-butadiene-styrene, polycarbonate, polystyrene, polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, nylons, polyamideimide, polyarylates, polyurethane, ethylene propylene rubber, ethylene propylene diene monomer, polyarylsulfone, polyethersulfone, polyphenylene ether, polyphenylene sulfide, polyvinyl chloride, polysulfone, polyetherimide, polytetrafluoroethylene, fluorinated ethylene propylene, perfluoroalkoxy, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polyetherketone, polyether etherketone, polyether ketone ketone; and mixtures comprising at least one of the foregoing thermoplastic or a thermoset selected from the group consisting of polyurethanes, natural rubber, synthetic rubber, epoxy, phenolic, polyesters, polyamides, silicones; and mixtures comprising at least one of the foregoing thermosets.  
     
     
         20 . The method of  claim 18 , wherein the vapor grown carbon fibers are selected from the group consisting of graphitic vapor grown carbon fibers, partially graphitic vapor grown carbon fibers, and mixtures comprising one of the foregoing vapor grown carbon fibers.  
     
     
         21 . The method of  claim 18 , wherein the vapor grown carbon fiber comprises about 0.25 to about 30 wt % of the total composition.  
     
     
         22 . The method of  claim 18 , wherein the carbon powder comprises about 0.25 to about 25 wt % of the total composition.  
     
     
         23 . The method of  claim 18 , wherein the carbon powder is carbon black.  
     
     
         24 . The method of  claim 18 , wherein the glass fiber is selected from the group consisting of E-glass, A-glass, C-glass, D-glass, R-glass, S-glass, and mixtures comprising at least one of the foregoing glass fibers and comprises up to about 50 wt % of the total composition.  
     
     
         25 . The method of  claim 18 , wherein the melt blending is conducted in processing equipment selected from the group consisting of extruders, roll mills, and dough mixers.  
     
     
         26 . The method of  claim 18 , wherein the extruded conductive pellet is further subjected to injection molding, blow molding, vacuum forming, and the like to form a conductive article.