Braided jackets with low thickness
Disclosed herein are methods for producing core-sheath structures by shaping at least one filament bundle containing a plurality of filaments to form at least one shaped strand of filaments, and braiding a plurality of strands, including the at least one shaped strand of filaments, over a core to form the core-sheath structure containing a braided sheath of the strands surrounding the core, wherein the shaped strand of filaments is an untwisted strand having a twist level of less than 1 turn per meter, a cross-sectional aspect ratio of the shaped strand of filaments is at least 3:1, as measured in the braided sheath, a thickness of at least a portion of the braided sheath ranges from about 10 to about 200 μm, and the braided sheath comprises a synthetic fiber having a tensile strength of greater than 12 cN/dtex. Also disclosed herein are core-sheath structures formed by such methods.
1. A cord having a core-sheath structure, comprising:
a core, and
a braided sheath of strands surrounding the core, the braided sheath comprising strands having a braid angle of 5° or more in a relaxed state,
wherein:
the strands having the braid angle of 5° or more in the relaxed state consist of shaped strands of filaments;
each shaped strand of filaments is an untwisted strand having a twist level of less than 1 turn per meter;
a cross-sectional aspect ratio of each shaped strand of filaments is at least 3:1, as measured in the braided sheath;
a thickness of at least a portion of the braided sheath ranges from about 20 to about 200 um; and
the braided sheath comprises a synthetic fiber having a tensile strength of greater than 12 cN/dtex.
2. The cord of claim 1 , wherein:
each shaped strand of filaments has a cross section including a curved surface;
each shaped strand of filaments has a cross section including a flat surface; or
a combination thereof.
3. The cord of claim 1 , wherein:
each shaped strand of filaments has an oval cross section;
each shaped strand of filaments has a curved cross section including a convex section and a concave section; or
each shaped strand of filaments is a flat fiber band having a cross section including a flat surface.
4. The cord of claim 1 , wherein each shaped strand of filaments includes at least one filament having a non-round cross section.
5. The cord of claim 1 , wherein each shaped strand of filaments is formed by tensioning a filament bundle over at least one surface.
6. The cord of claim 1 , wherein each shaped strand of filaments is formed by tensioning a filament bundle over at least one curved surface such that the filaments separate from one another to form a flat fiber band.
7. The cord of claim 1 , wherein each shaped strand of filaments is formed by squeezing a filament bundle between two surfaces.
8. The cord of claim 1 , wherein a maximum diameter of the cord ranges from about 40 μm to less than about 5 mm.
9. The cord of claim 1 , wherein a ratio of a maximum diameter of the braided sheath to a minimum diameter of the braided sheath ranges from 1.05:1.0 to 2.5:1.0.
10. The cord of claim 1 , wherein each shaped strand of filaments has a flattening factor (F) ranging from 0.05 to 0.45, where the flattening factor (F) is defined as follows:
F
=
(
D
max
-
D
min
)
2
D
s
in which:
D max is a maximum diameter of the braided sheath, as measured in a cross-sectional plane of the cord that is perpendicular to a longitudinal axis of the cord, in micrometers (μm);
D min is a minimum diameter of the braided sheath, as measured in the cross-sectional plane of the cord that is perpendicular to the longitudinal axis of the cord, in micrometers (μm); and
D s is a minimum diameter of the filament bundle prior to the shaping, as measured in a cross-sectional plane of the filament bundle that is perpendicular to a longitudinal axis of the filament bundle, in micrometers (μm).
11. The cord of claim 1 , wherein the core is a braided core.
12. The cord of claim 1 , wherein at least one of the shaped strands of filaments further comprises a lubricant, a fiber, a surface-coated filament, or combinations thereof.
13. The cord of claim 1 , wherein a tensile strength of at least one of the shaped strands of filaments is greater than 12 cN/dtex.
14. The cord of claim 1 , wherein at least one of the shaped strands of filaments comprises at least one selected from the group consisting of a liquid crystalline polyester filament, an aramid filament, co-polymer aramid filament, a polyether ether ketone filament, a poly(p-phenylene benzobisoxazole) filament, an ultra-high molecular weight polyethylene filament, a high modulus polyethylene filament, a polypropylene filament, a polyethylene terephthalate filament, a polyamide filament, a polyhydroquinone diimidazopyridine filament, and a high-strength polyvinyl alcohol filament.
15. The cord of claim 1 , wherein at least one of the shaped strands of filaments comprises a co-polymer aramid filament.
16. The cord of claim 1 , wherein the core comprises at least one selected from the group consisting of a liquid crystalline polyester filament, an aramid filament, co-polymer aramid filament, a polyether ether ketone filament, a poly(phenylene benzobisoxazole) filament, an ultra-high molecular weight polyethylene filament, a polypropylene filament, a high modulus polyethylene filament, a polyethylene terephthalate filament, a polyamide filament, and a high-strength polyvinyl alcohol filament.