3-D printed fluoropolymer structures
The invention relates to fluoropolymer filament for use in 3-D printing, and 3-D printed fluoropolymer articles having low warpage, excellent chemical resistance, excellent water resistance, flame resistance, and good mechanical integrity. Additionally, the articles of the invention have good shelf life without the need for special packaging. In particular, the invention relates to filament, 3-D printed polyvinylidene fluoride (PVDF) articles, and in particular material extrusion 3-D printing. The articles may be formed from PVDF homopolymers, copolymers, such as KYNAR® resins from Arkema, as well as polymer blends with appropriately defined low shear melt viscosity. The PVDF may optionally be a filled PVDF formulation. The physical properties of the 3-D printed articles can be maximized and warpage minimized by optimizing processing parameters.
1. A three-dimensionally printed fluoropolymer article, comprising a fluoropolymer composition, wherein said fluoropolymer composition comprises a fluoropolymer comprising either a homopolymer of vinylidene fluoride, or a copolymer comprising at least 65 weight percent of vinylidene fluoride monomer units, and one or more comonomers, wherein said fluoropolymer has a low shear rate viscosity at 232° C. and 4 sec −1 of less than 10,000 Pa-s, as measured by capillary rheomometry and a high shear rate viscosity of 30 to 2000 Pa-s at 232° C. and 100 sec −1 , as measured by capillary rheomometry at the temperature given in the ASTM Melt Flow Testing for that fluoropolymer; and wherein the article comprises layers of the fluoropolymer composition that are not laser sintered.
2. The fluoropolymer article of claim 1 , wherein said fluoropolymer composition further comprises from 0.01 to 50 weight percent of one or more fillers, based on the weight of the fluoropolymer and filler.
3. The fluoropolymer article of claim 2 , wherein said filler is selected from the group consisting of carbon fiber, milled carbon fiber, carbon powder, carbon nanotubes, glass beads, glass fibers, nano-silica, Aramid fiber, polyaryl ether ketone fibers, BaSO 4 , talc, CaCO 3 , graphene, impact modifiers, nano-fibers, and hollow spheres, and mixtures thereof.
4. The fluoropolymer article of claim 2 , wherein said fluoropolymer composition further comprises from 0.01 to 30 weight percent of one or more fillers, based on the weight of the fluoropolymer and filler.
5. The fluoropolymer article of claim 1 , wherein said fluoropolymer composition comprises a blend of said fluoropolymer and up to 49 weight percent of one or more other compatible polymers.
6. The fluoropolymer article of claim 5 , wherein said other compatible polymer is selected from a different fluoropolymer, a polymethyl methacrylate homopolymer or copolymer, or a block copolymer with one or more compatible blocks and at least one incompatible block.
7. The fluoropolymer article of claim 5 , wherein blend comprises at least two chemically different fluoropolymers, and/or fluoropolymers of differing weight average molecular weights wherein said weight average viscosity of the blend is less than 13,000 Pa-s.
8. The fluoropolymer article of claim 1 , wherein in the copolymer, the one or more comonomers are selected from the group consisting of tetrafluoroethylene (TFE), trifluoroethylene (TrFE), chlorotrifluoroethylene (CTTE), dichlorodifluoroethylene, hexafluoropropene (HFP), vinyl fluoride (VF), hexafluoroisobutylene (HFIB), perfluorobutylethylene (PFBE), 1,2,3,3,3-pentafluoropropene, 3,3,3-trifluoro-1-propene, 2-trifluoromethyl-3,3,3-trifluoropropene, 2,3,3,3-tetrafluoropropene, 1-chloro-3,3,3-trifluoropropene, fluorinated vinyl ethers, fluorinated dioxoles, partially- or per-fluorinated alpha olefins of C 4 and higher, partially- or per-fluorinated cyclic alkenes of C 3 and higher, and combinations thereof.
9. The three-dimensionally printed fluoropolymer article of claim 1 , wherein said article has an elongation at break of greater than 700% as measured in the xy direction.
10. The three-dimensionally printed fluoropolymer article of claim 1 , wherein said article has an elongation at break of greater than 70 percent and also greater than 1500 psi stress at yield when printed and tested in the xy direction.
11. The three-dimensionally printed fluoropolymer article of claim 1 , wherein said article has a elongation at break of greater than 70 percent, and also greater than 3500 psi stress at yield when printed and tested in the xy direction.
12. The three-dimensionally printed fluoropolymer article of claim 1 , having one or more different compatible polymer compositions as a base layer, wherein said base layer is less warping than the fluoropolymer composition layer on top of the base layer.
13. The three-dimensionally printed fluoropolymer article of claim 1 , wherein two or more fluoropolymers compositions with different stress modulus, and two or more nozzles are used, producing a mechanically asymmetric part made using a rigid and a flexible fluoropolymer whereby one direction (x) is rigid and the other direction (y) is flexible.
14. The three-dimensionally printed fluoropolymer article of claim 1 , wherein said article is cross-linked after printing by radiation.