Discontinuous-fiber composites and methods of making the same
The invention relates to compositions comprising composite materials comprised of discontinuous fibers and one or more polymers and/or oligomers. The invention relates to methods of making the same. The composite materials can be in the form of compositions, composite sheets, laminates, pellets, and/or shaped composite products.
1. A method for preparing a polymer composite composition comprising:
mixing discontinuous fibers and one or more polymers and/or oligomers to form a mixture in an extruder; wherein the discontinuous fibers have a minimum length of about 0.16 inches when added to the extruder; wherein said polymer and/or oligomer is a thermoplastic or a thermoset; and wherein said discontinuous fibers are aramid fibers, carbon fibers, ceramic fibers, glass fibers, polymeric fibers, or mineral-based fibers, or a combination thereof
rolling the mixture to form the polymer composite composition into a sheet, wherein the rolling orients the discontinuous fibers in one direction; and
wherein one or more stages of the method minimize the fiber length attrition.
2. The method of claim 1 , wherein said extruder is a single-screw or twin-screw extruder.
3. The method of claim 1 , wherein the method further comprises drawing the sheet after the rolling step, and wherein the drawing further orients the discontinuous fibers in the same direction.
4. The method of claim 1 , wherein the discontinuous fiber is present in the composite sheet at a load of between about 2 wt. % and about 75 wt. %; and wherein the polymer and/or oligomer can be present in the composite at a load of between about 25 wt. % and about 98 wt. %.
5. The method of claim 1 , wherein the extruder feeds into a rolling process through a die that is larger than the extruder opening, through a die that is the same size as the extruder opening, or without passing the extrudate through a die.
6. The method of claim 1 , further comprising laminating the sheet to form a laminate.
7. The method of claim 6 , wherein the laminate further comprises a composite sheet prepared by a different method, a polymer sheet, a metal sheet, or combinations thereof.
8. The method of claim 1 wherein the said mixing occurs during partial or complete in-situ polymerization of a monomer and/or oligomer.
9. The method of claim 1 , wherein the rolling step is performed between two or more rollers.
10. The method of claim 1 , wherein the rolling step is performed between multiple sets of rollers.
11. The method of claim 1 wherein the combining step further comprising combining additional ingredients; and wherein the mixing step further comprising mixing additional ingredients.
12. The method of claim 1 further comprising chipping the composite sheet to form pellets.
13. The method of claim 1 further comprising forming a shaped composite product.
14. The method of claim 13 , wherein the forming step is compression molding, pressure forming, thermoforming, or injection molding.