ZBREHON

Unidirectional Carbon Fiber

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3K, 12K or 24K: which carbon fiber tow and grade should I choose?

Choose the tow size by your process and the grade by the stiffness you need. Zbrehon’s carbon fiber roving is continuous PAN-based tow in 3K, 12K and 24K, used for weaving, pultrusion, filament winding and composite reinforcement[1].

What does the K number change?

K is the number of filaments in thousands, so it sets how much fiber each strand carries. You can see it in the linear density. 3K weighs 198 g/km[2], 12K weighs 800 g/km[3] and 24K weighs 1,600 g/km[4] in the same grade family.

  • 3K: finer weaves and visible cosmetic surfaces.
  • 12K: the common size for pultrusion, filament winding and heavier fabrics.
  • 24K: puts down the most fiber per pass when cost per kilogram and speed matter more than surface look.

Which grade fits?

Standard-modulus grades are around 230 GPa. Tensile strength ranges from 4,000 MPa[2] to 4,900 MPa[5].

Higher-strength grades reach 5,900 MPa at 295 GPa[6], and 6,400 MPa at 295 GPa[7].

For stiffness-driven parts, the SYM grades raise modulus to 280 GPa[8], 330 GPa[9] and 375 GPa[10]. Elongation at break falls as modulus rises, to 1.2% on SYM40[10]. A stiffer fiber is less forgiving under impact.

What if I need short fiber instead?

For injection molding, plastic modification, ESD and EMI shielding, use chopped strand instead of roving[11]. Standard lengths are 3, 6 and 12 mm, with custom lengths from 1 to 50 mm[12]. The sizing can be epoxy, polyurethane or polyamide to match your resin or polymer[13].

What to put in your inquiry

  • Process: weaving, pultrusion, filament winding, prepreg or compounding.
  • Tow size and grade code, or the tensile strength and modulus you need.
  • Sizing type and monthly quantity in kilograms.

Send it through the quote form. See the chopped strand page for short fiber.

Sources

  1. Carbon fiber roving is continuous PAN-based carbon fiber tow in 3K, 12K and 24K. It is the feedstock for weaving, pultrusion, filament winding and composite…
  2. SYT45: Model: SYT45; Tow: 3K; Tensile strength (MPa): 4000; Modulus (GPa): 230; Linear density (g/km): 198; Elongation at break (%): 1.7
  3. SYT45S: Model: SYT45S; Tow: 12K; Tensile strength (MPa): 4500; Modulus (GPa): 230; Linear density (g/km): 800; Elongation at break (%): 1.9
  4. SYT45S: Model: SYT45S; Tow: 24K; Tensile strength (MPa): 4500; Modulus (GPa): 230; Linear density (g/km): 1600; Elongation at break (%): 1.9
  5. SYT49S: Model: SYT49S; Tow: 12K; Tensile strength (MPa): 4900; Modulus (GPa): 230; Linear density (g/km): 800; Elongation at break (%): 2.1
  6. SYT55S: Model: SYT55S; Tow: 12K; Tensile strength (MPa): 5900; Modulus (GPa): 295; Linear density (g/km): 450; Elongation at break (%): 2.0
  7. SYT65: Model: SYT65; Tow: 12K; Tensile strength (MPa): 6400; Modulus (GPa): 295; Linear density (g/km): 450; Elongation at break (%): 2.1
  8. SYM30: Model: SYM30; Tow: 12K; Tensile strength (MPa): 4500; Modulus (GPa): 280; Linear density (g/km): 740; Elongation at break (%): 1.5
  9. SYM35: Model: SYM35; Tow: 12K; Tensile strength (MPa): 4700; Modulus (GPa): 330; Linear density (g/km): 450; Elongation at break (%): 1.4
  10. SYM40: Model: SYM40; Tow: 12K; Tensile strength (MPa): 4700; Modulus (GPa): 375; Linear density (g/km): 430; Elongation at break (%): 1.2
  11. Application: Item: Application; Parameter: Plastic modification, injection molding, ESD, EMI shielding, resin reinforcement
  12. Available length: Item: Available length; Parameter: 3 mm / 6 mm / 12 mm; custom 1–50 mm
  13. Sizing agent: Item: Sizing agent; Parameter: Epoxy (EP) / Polyurethane (PU) / Polyamide (PA), optional

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