Method for making thermally-conductive plastic articles having light reflecting surfaces

Abstract

A method for making molded reflector articles having light-reflecting surfaces is provided. The method involves injection-molding a thermally-conductive, polymer composition comprising: a) about 20% to about 80% by weight of a base polymer matrix such as polycarbonate; and b) about 20% to about 80% by weight of a thermally-conductive carbon material such as graphite. The method can be used to make reflector articles such as housings for automotive tail lamps, head lamps, and other lighting fixtures.

1 . A method of making a net-shape molded, thermally-conductive reflector article having a light-reflecting surface, comprising the steps of: 
 a) providing a molten polymer composition comprising: i) about 20% to about 80% by weight of a base polymer matrix; and ii) about 20% to about 80% by weight of a thermally-conductive carbon material;    b) injecting the molten composition into a mold to form a net-shape molded, thermally-conductive reflector article; and    c) removing the reflector article from the mold.    
   
   
       2 . The method of  claim 1 , wherein the polymer matrix comprises a thermoplastic polymer.  
   
   
       3 . The method of  claim 1 , wherein the thermoplastic polymer is selected from the group consisting of polycarbonates, polyethylene, polypropylene, acrylics, vinyls, fluorocarbons, polyamides, polyphenylene sulfide, and liquid crystal polymers.  
   
   
       4 . The method of  claim 1 , wherein the polymer matrix comprises a thermosetting polymer.  
   
   
       5 . The method of  claim 1 , wherein the thermosetting polymer is selected from the group consisting of elastomers, epoxies, polyesters, polyimides, and acrylonitriles.  
   
   
       6 . The method of  claim 1 , wherein the thermally-conductive material is in the form of particles.  
   
   
       7 . The method of  claim 1 , wherein the thermally-conductive carbon material is selected from the group consisting of graphite, carbon black, and carbon fibers.  
   
   
       8 . The method of  claim 1 , wherein the polymer composition further comprises about 5% to about 30% by weight of a reinforcing material.  
   
   
       9 . The method of  claim 8 , wherein the reinforcing material is glass.  
   
   
       10 . The method of  claim 1 , wherein the polymer composition further comprises an additive selected from the group consisting of antioxidants, plasticizers, stabilizers, dispersing agents, coloring agents, and mold-releasing agents.  
   
   
       11 . The method of  claim 1 , wherein the polymer composition comprises about 74% by weight of polycarbonate, about 24% by weight of carbon graphite, and about 1% by weight of mold-releasing agent.