Polymer/carbon-nanotube interpenetrating networks and process for making same

Abstract

The present invention is directed to new methods for combining, processing, and modifying existing materials, resulting in novel products with enhanced mechanical, electrical and electronic properties. The present invention provides for polymer/carbon nanotube composites with increased strength and toughness; beneficial for lighter and/or stronger structural components for terrestrial and aerospace applications, electrically and thermally conductive polymer composites, and electrostatic dissipative materials. Such composites rely on a molecular interpenetration between entangled single-wall carbon nanotubes (SWNTs) and cross-linked polymers to a degree not possible with previous processes.

1 . A B-stage powder comprising:
 a) CNTs;   b) a polymer material that forms interpenetrating networks with the CNTs, wherein the polymer material is at least partially cured to an extent so as to prevent a re-bundling of the CNTs; and   c) at least one un-activated curing agent capable of further curing the polymeric material.   
     
     
         2 . The B-stage powder of  claim 1 , wherein the CNTs are SWNTs. 
     
     
         3 . The B-stage powder of  claim 1 , wherein the CNTs are functionalized. 
     
     
         4 . The B-stage powder of  claim 2 , wherein the SWNTs are functionalized. 
     
     
         5 . The B-stage powder of  claim 1 , wherein the polymer material is selected from the group consisting of epoxy resins, unsaturated polyester resins, vinyl ester resins, and combinations thereof. 
     
     
         6 . The B-stage powder of  claim 1 , wherein the unactivated curing agent is selected from the group consisting of aromatic amines, diaminodiphenyl sulfone, acid dianhydrides, boron trifluoride monoethylamine complexes, and combinations thereof. 
     
     
         7 . The B-stage powder of  claim 1 , wherein the powder is comprised of particles having a size that ranges from about 1 micron to about 100 microns. 
     
     
         8 . A process comprising the steps of:
 a) providing a plurality of B-stage particles comprising partially cured polymer material; and   b) further curing the polymer material to form bulk objects comprising interpenetrating networks of CNTs and polymeric material.   
     
     
         9 . The process of  claim 8  further comprising a step of incipient-wetting the B-stage particles with additional CNT material. 
     
     
         10 . The process of  claim 8 , further comprising a step of adding additional polymeric material to the B-stage particles. 
     
     
         11 . The process of  claim 8 , wherein the step of further curing is done during a process selected from the group consisting of high-shear extrusion processes and injection molding. 
     
     
         12 . The process of  claim 8 , wherein the step of further curing is done in conjunction with solid free-form fabrication. 
     
     
         13 . The process of  claim 8 , wherein the step of further curing is done in conjunction with at least one rapid prototyping technique. 
     
     
         14 . A polymer/CNT composite comprising interpenetrating networks, wherein the composite is made by a process comprising the steps of:
 a) introducing CNTs and prepolymer molecules into a solvent to form a solvent mixture;   b) atomizing the solvent mixture into micro-droplets via spraying;   c) rapidly removing the solvent from the micro-droplets and, simultaneously, at least partially curing the prepolymer to provide solid polymer/CNT particles; and   d) depositing the solid polymer/CNT particles on a surface to form a polymer/CNT composite layer.   
     
     
         15 . The polymer/CNT composite of  claim 14 , wherein the CNTs are SWNTs. 
     
     
         16 . The polymer/CNT composite of  claim 14 , wherein the CNTs are functionalized. 
     
     
         17 . The polymer/CNT composite of  claim 14 , wherein the prepolymer is selected from the group consisting of epoxy resins, unsaturated polyester resins, vinyl ester resins, and combinations thereof. 
     
     
         18 . The polymer/CNT composite of  claim 14 , wherein the prepolymer is at least partially cured using at least one curing agent selected from the group consisting of di-amines, poly-amines, imidazoles, and combinations thereof. 
     
     
         19 . The polymer/CNT composite of  claim 14 , wherein the step of introducing involves a technique selected from the group consisting of sonication, mechanical shear, heating, and combinations thereof. 
     
     
         20 . The polymer/CNT composite of  claim 14 , wherein the step of rapidly removing solvent comprises exposure to a condition selected from the group consisting of heating, mechanical pumping, evacuation, and combinations thereof. 
     
     
         21 . The polymer/CNT composite of  claim 14 , wherein the step of depositing the particles is done with heat to effect crosslinking. 
     
     
         22 . The polymer/CNT composite of  claim 14 , wherein the solid polymer/CNT particles have a size that ranges from about 1 micron to about 100 microns. 
     
     
         23 . The polymer/CNT composite of  claim 14 , wherein the CNTs are preferentially oriented within the composite. 
     
     
         24 . The polymer/CNT composite of  claim 23 , wherein the preferential orientation is the result of extrusion, protrusion, or other processes used to orient fibrous reinforcement in polymers. 
     
     
         25 . The polymer/CNT composite of  claim 14 , wherein CNT concentration within the polymer/CNT composite layer is graded in a particular direction. 
     
     
         26 . The polymer/CNT composite of  claim 14 , wherein CNT concentration within the polymer/CNT composite layer is modulated with alternating polymer/CNT sublayers of differing CNT concentration.