Method for producing heterogeneous composites

Abstract

A method for selecting materials and processing conditions to prepare a heterogeneous structure in situ via the reaction of a homogeneous mixture of a reactive organic compound and a filler, which may then optionally be sintered. The method is employed to provide a heterogeneous composite possessing exceptionally high thermal and/or electrically conductivities for a given concentration of conductive filler. The choice of materials as well as processing conditions employed, as will be described below, have a strong effect on the rate domain formation/heterogeneity of the structure formed, the extent of filler particle-particle interactions within filler-rich domains, and ultimately the thermal and/or electrical conductivity. Proper choice of these conditions can lead to composites having enhanced properties at a reduced bulk filler concentration.

1 . A method for producing a composite comprising:
 a) selecting a reactive organic compound;   b) selecting an inorganic filler component;   c) mixing the reactive organic compound and the inorganic filler component, wherein at room temperature the organic compound and the filler component mix to form a substantially homogeneous structure having a bulk filler concentration; and,   d) reacting the organic compound to form a polymer;   
     wherein the polymer has a repulsive interaction with the inorganic filler thereby creating, in situ, a heterogeneous structure comprising filler rich domains. 
   
   
       2 . The method of  claim 1 , wherein the concentration of the filler is higher than that of a bulk filler concentration. 
   
   
       3 . The method of  claim 1 , wherein the reactive organic compound comprises at least one of monomers, oligomers, prepolymers, or reactive polymers. 
   
   
       4 . The method of  claim 3 , wherein the organic compound further comprises a cure agent. 
   
   
       5 . The method of  claim 1 , wherein the reaction of step d) is advanced by heating the mixture. 
   
   
       6 . The method of  claim 1 , wherein the reaction of step d) is advanced by exposing the mixture to activating ultraviolet radiation. 
   
   
       7 . The method of  claim 1 , further comprising a second filler component. 
   
   
       8 . The method of  claim 7 , wherein the second filler component resides substantially with the polymer after the organic compound has been reacted. 
   
   
       9 . The method of  claim 1 , wherein the inorganic filler component comprises an inorganic filler coated with an organic coating. 
   
   
       10 . The method of  claim 9 , wherein the organic coating on the filler has an affinity for the reactive organic compound. 
   
   
       11 . The method of  claim 9 , wherein the coating on the filler comprises stearic acid. 
   
   
       12 . The method of  claim 9 , wherein the coating on the filler is present in a single layer as averaged over substantially all of the filler. 
   
   
       13 . The method of  claim 9 , wherein the organic coating on the filler has a repulsive interaction with the new polymer formed from the step of reacting the organic component. 
   
   
       14 . The method of  claim 9 , wherein the coating on the filler comprises a non-polar coating. 
   
   
       15 . The method of  claim 1 , wherein the polymer formed during step d) comprises polar moieties. 
   
   
       16 . The method of  claim 1 , wherein the filler is thermally conductive. 
   
   
       17 . The method of  claim 1 , wherein the filler is electrically conductive. 
   
   
       18 . The method of  claim 1 , wherein the filler comprises solder. 
   
   
       19 . The method of  claim 1 , wherein the filler comprises less than 75 percent by weight based on the total weight of the composition. 
   
   
       20 . The method of  claim 1 , wherein the filler comprises less than 50 percent by volume based on the total volume of the composition. 
   
   
       21 . The method of  claim 1 , wherein the filler comprises at metallic filler of at least one of nickel, copper, silver, palladium, platinum, gold, and alloys thereof. 
   
   
       22 . The method of  claim 1 , wherein the filler comprises a cold worked silver flake. 
   
   
       23 . The method of  claim 1 , wherein the filler comprises a sinterable filler. 
   
   
       24 . The method of  claim 23 , further comprising the step of sintering the filler particles together. 
   
   
       25 . The method of  claim 24 , wherein the step of sintering the filler particles together and the step of reacting the organic compound are performed simultaneously. 
   
   
       26 . The method of  claim 23 , wherein substantially all of the sinterable filler particles that are in direct contact with one another are sintered. 
   
   
       27 . The method of  claim 24 , wherein the step of sintering is performed at a temperature above approximately 100° C. 
   
   
       28 . The method of  claim 24 , wherein the step of sintering is performed at a temperature of above approximately 150° C. 
   
   
       29 . The method of  claim 24 , wherein the sintering step is enhanced by an applied pressure on the composition. 
   
   
       30 . The method of  claim 24 , wherein the degree of sintering is regulated through selection of sintering temperature and pressure. 
   
   
       31 . The method of  claim 1 , wherein the mixture of the reactive organic component and the filler is a solvent-free 100% solids composition.