High modulus polymer composites and methods of making the same

Abstract

The invention provides methods of producing composite polymers by combining fillers with polymers in the presence of preformed high molecular weight polymer. Monomer polymerization can be initiated through the addition of initiators or by reactive chemical groups on the surface of the fibers. The composite materials formed possess superior mechanical properties compared to similar polymer composites made by either purely mechanical mixing or solely polymerization of monomers in the presence of the fillers.

1 . A method comprising: 
 mixing a filler simultaneously with a monomer that can react to form a grafted polymer layer on the surface of the filler and a pre-formed polymer;    wherein an interchange reaction takes place between a grafted layer on the surface of the filler and the pre-formed polymer to form a composite polymer.    
   
   
       2 . The method of  claim 1 , wherein the filler is an organic filler.  
   
   
       3 . The method of  claim 2 , wherein the filler is selected from the group consisting of wood fiber, wood flour, starch, straws, bagasse, coconut hull/fiber, cork, corn cob, corn stover, cotton, gilsonite, nutshell, nutshell-flour, rice hull, sisal, hemp, and soybean.  
   
   
       4 . The method of  claim 1 , wherein the filler is an inorganic filler.  
   
   
       5 . The method of  claim 4 , wherein the filler is selected from the group consisting of a mineral, calcium carbonate, montmorilonite, kaolin, titanium dioxide, alumina trihydrate, Wollastonite, talc, silica, quartz, barium sulfate, antimony oxide, mica, magnesium hydroxide, calcium sulfate, feldspar, nepheline syenite, microspheres, carbon black, glass, glass fibers, carbon fibers, metallic particles, magnetic particles, montmorillonite, buckminsterfullerene, carbon nanotubes, carbon nanoparticles, silicas, cellulosic nanofibers, synthetic silicates, and synthetically prepared nanoparticles.  
   
   
       6 . The method of  claim 1 , wherein the filler is cellulose that has been pretreated with alkali prior to the mixing.  
   
   
       7 . The method of  claim 1 , wherein the monomer is selected from the group consisting of L-lactide, D-lactide, LD-lactide, caprolactone, caprolactam, ring opening monomers, ethylene glycol-terphthalic acid, sebacoyl chloride—1,6 hexadiamine, step reaction monomers, ethylene, propylene, styrene, methyl methacrylate, and vinyl monomers.  
   
   
       8 . The method of  claim 1 , wherein the pre-formed polymer is selected from the group consisting of poly-lactic acid (PLA), polycaprolactone, poly(ethylene terephthalate), polyesters, polycaprolactam (Nylon 6), poly(hexamethyl sebacamide) (Nylon 6,10), polyamides, polyurethanes, polycarbonates, polyolefins, polyethylene, polybutadiene, polypropylene, polystyrene, and polymethylmethacrylate.  
   
   
       9 . The method of  claim 1 , wherein the mixing is conducted in the presence of a catalyst that initiates or catalyzes the polymerization reaction.  
   
   
       10 . The method of  claim 1 , wherein the mixing is conducted in the presence of a catalyst that catalyzes the interchange reaction between the monomer and the pre-formed polymer on the surface of the filler.  
   
   
       11 . The method of claims  9  or  10 , further comprising stopping a polymer reaction by contacting the pre-formed polymer with a compound that deactivates the catalyst.  
   
   
       12 . The method of  claim 10 , wherein the catalyst is selected from the group consisting of titanium(IV) isopropoxide (TIP), dibutyl tin oxide (DBTO), an alkyl tin(IV) compound, monobutyltin trichloride (BuSnCl 3 ), TBD (1,5,7-triazabiscyclo(4.4.0)dec-5-ene), acid catalysts, sulfonic and sulfuric acids, base catalysts, sodium methylate, sodium methoxide, potassium methoxide, sodium hydroxide and potassium hydroxide, organic bases, triethylamine, piperidine, 1,2,2,6,6-pentamethylpiperidine, pyridine, 2,6-di-tert-butylpiridine, 1,3-Disubstituted tetrakis(fluoroalkyl)distannoxanes, 4-dimethyl-aminopyridine (DMAP) and guanidine, alkaline metal alkoxides and hydroxides, basic zeolites, cesium-exchanged NaX faujasites, mixed magnesium-aluminum oxides, magenesium oxide and barium hydroxide, 4-(dimethylamino)pyridine (DMAP), 4-pyrolidinopyridine (PPY), salts of amino acids, and enzyme transesterification catalysts.  
   
   
       13 . The method of  claim 1 , wherein the monomer is lactide and the pre-formed polymer is polylactide.  
   
   
       14 . The method of  claim 1 , wherein the monomer is ethylene glycol-terphthalic acid and the pre-formed polymer is poly(ethylene terphthalate).  
   
   
       15 . The method of  claim 1 , wherein the monomer is ethylene and the pre-formed polymer is polyethylene.  
   
   
       16 . The method of  claim 1 , wherein the monomer is an ester and the pre-formed polymer is a poly(ester).  
   
   
       17 . The method of  claim 1 , wherein the monomer is a polycarbonate and the pre-formed polymer is a poly(ester).  
   
   
       18 . The method of  claim 1 , wherein the monomer is a polyamide and the pre-formed polymer is a poly(ester).  
   
   
       19 . A method comprising: 
 mixing cellulose fibers with lactide and polylactic acid to form a premix    contacting the premix with a composition comprising stannous octoate, triphenylphospine, and titanium isopropoxide, to produce a composite polymer    contacting the composite polymer with poly(acrylic acid) to form a stabilized composite polymer.    
   
   
       20 . A composite polymer made by mixing a filler simultaneously with 1) a monomer that can react to form a grafted polymer layer on the surface of the filler and 2) a pre-formed polymer, 
 wherein an interchange reaction takes place between a grafted layer on the surface of the filler and the pre-formed polymer to form a composite polymer.    
   
   
       21 . The polymer of  claim 20 , wherein the filler is cellulose, the monomer is lactide and the pre-formed polymer is poly-lactic acid (PLA).  
   
   
       22 . The polymer of  claim 21 , wherein the mixing is conducted in the presence of a catalyst selected from the group consisting of titanium(IV) isopropoxide (TIP), stannous octoate Sn(Oct) 2 , triphenylphospine, and mixtures thereof.