Low shear process for producing polymer composite fibers
A method for producing a polymer composite fiber comprised of a polymer matrix with filaments incorporated therein whose lengthwise dimensions are substantially oriented with the axial dimension of the composite fiber, the method comprising subjecting a melt comprised of a polymer matrix and filaments to an extrusion process in which the melt is extruded into a fibrous form in the absence of screw extruders and in the substantial absence of shear forces that result in breakage of the filaments, followed by cooling and solidification of the extruded melt to provide the polymer composite fiber. Integration of these polymer composite fibers with additive manufacturing technologies, particularly rapid prototyping methods, such as FFF and 3D printing, are also described. The resulting polymer composite fibers and articles made thereof are also described.
1. A method for producing an object from a polymer composite fiber comprising a polymer matrix with filaments incorporated therein whose lengthwise dimensions are substantially oriented with the axial dimension of the composite fiber, the method comprising subjecting a melt comprising a polymer matrix and filaments homogeneously distributed throughout said polymer matrix to an extrusion process in which the melt is extruded into a fibrous form in the absence of screw extruders and in the substantial absence of shear forces that result in breakage of said filaments, followed by cooling and solidification of the extruded melt to provide the polymer composite fiber, wherein the polymer composite fiber, as produced above, is fed into an additive manufacturing unit to produce said object made of said polymer composite fiber by additive manufacturing.
2. The method of claim 1 , wherein said melt is first produced by a compounding process in which polymer matrix material and filament material are mixed and heated to at least the melting point of the polymer matrix material to form said melt.
3. The method of claim 1 , wherein the melt is extruded by a melt spinning process.
4. The method of claim 1 , wherein the melt is extruded by pushing the melt through a die by means of a plunger that moves at a substantially fixed speed to provide a substantially constant pressure on the melt moving through the die.
5. The method of claim 1 , wherein said polymer matrix has a composition comprising a polyamide, polyester, polyacrylonitrile, polyolefin, lignin, polycarbonate, polystyrene, polybutadiene, polyphenylsulfone, polyether, polybenzimidazole, viscose, rayon, pitch, or combination thereof.
6. The method of claim 1 , wherein said polymer matrix is comprised of acrylonitrile-butadiene-styrene.
7. The method of claim 1 , wherein said filaments are composed of carbon, metal oxide, or metal.
8. The method of claim 1 , wherein said filaments are carbon filaments.
9. The method of claim 8 , wherein said carbon filaments are selected from micron-sized carbon fibers, carbon nanofibers, carbon nanotubes, platelet nanofibers, and graphene nanoribbons.
10. The method of claim 1 , wherein said filaments are coated with a sizing agent.
11. The method of claim 1 , wherein said filaments are carbon filaments coated with an epoxy-based sizing agent.
12. The method of claim 1 , wherein said filaments are included in an amount of at least 1 wt % and up to 40 wt %.
13. The method of claim 1 , wherein said filaments are included in an amount of at least 5 wt % and up to 35 wt %.
14. The method of claim 1 , wherein said filaments are included in an amount of at least 10 wt % and up to 30 wt %.
15. The method of claim 1 , wherein said filaments have a length to diameter ratio of at least 10:1.
16. The method of claim 1 , wherein said filaments have a length to diameter ratio of at least 100:1.
17. The method of claim 1 , wherein said filaments have a length of at least 100 nm and up to 1 mm.
18. The method of claim 1 , wherein said melt includes a plasticizer.
19. The method of claim 1 , wherein said additive manufacturing unit is a rapid prototyping unit.
20. The method of claim 19 , wherein said rapid prototyping unit is a 3D printer.