Pre-oxidized fiber knitted fabric, also known as pre-oxidized fiber fabric or Panox knitted fabric, is a special textile made from pre-oxidized fiber (Panox) as the base material. Pre-oxidized fiber itself is an intermediate product obtained by stabilizing polyacrylonitrile (PAN) fibers under high temperatures, serving as the precursor for carbon fiber production. This material usually appears black, with excellent flexibility, high-temperature resistance, and non-flammability.
The knitted fabric made from Panox combines the inherent superior properties of the fiber with the unique structure of knitted textiles, resulting in a special flame retardant fabric that offers high flame resistance, outstanding thermal stability, and good comfort. Its Limiting Oxygen Index (LOI) is usually greater than 45%, and during combustion, it does not melt, shrink, or produce molten droplets. This makes it an advanced fabric flame-retardant material with high reliability.
Manufacturing Process
The production of pre-oxidized fiber knitted fabric is a multi-step precision process, mainly including the following stages:
- Spinning Dope Preparation: Acrylonitrile monomer and comonomers (such as methyl acrylate) are copolymerized in solvent at a typical ratio of 94:4 to produce spinning dope. Common solvents include 1-butyl-3-methylimidazolium tetrafluoroborate.
- Fiber Formation: Using the dry-wet spinning method, the spinning solution is extruded into nascent fibers. Compared with conventional wet spinning, this method is faster and allows the use of larger spinneret orifices and higher concentration/viscosity dope, leading to smooth-surfaced filaments without grooves.
- Fiber Processing: Nascent fibers undergo drawing, washing, oiling, and densification drying to form precursor fibers. Drawing aligns PAN molecular chains along the fiber axis, improving orientation and enhancing mechanical performance.
- Pre-Oxidation: Precursor fibers are placed in an air oxidation furnace with a temperature gradient of 180°C–300°C, where they undergo pre-oxidation to form Panox. This is the critical step in creating a thermally stable structure.
- Spinning into Yarn: The pre-oxidized fibers are spun into Panox yarn. While maintaining a high LOI, the fibers exhibit good spinnability.
- Knitting: Panox yarns are knitted into fabrics. Knitting provides elasticity and comfort. Panox can also be blended with aramid or other flame retardant fabrics for enhanced performance.
Technical Parameters
| Category | Specific Index | Value Range/Standard |
|---|---|---|
| Physical Properties | Limiting Oxygen Index (LOI) | 35%–55% (typically >45%) |
| Density | ~1.4 | |
| Weight | 220–400 g/m² (customizable) | |
| Width | 1–2.1 m (customizable) | |
| Mechanical Properties | Breaking Strength (warp) | ≥600 N |
| Breaking Strength (weft) | ≥450 N | |
| Elongation at Break | ~12% | |
| Thermal Properties | Long-term Service Temp. | Up to 220°C, no aging/shrinkage |
| Short-term Heat Resistance | Withstands 1000°C, non-burning | |
| Electrical Properties | Resistivity | ~8 × 10⁸ ohm·cm (antistatic) |
| Chemical Stability | Acid/Alkali Resistance | Excellent |
| Environmental Properties | Moisture Absorption | <5% |
| Thermal Conductivity | ~0.05 W/m·K |
Application Fields
Thanks to its outstanding performance, heat resistant fabric made from pre-oxidized fiber is widely applied across many industries:
- Protective Clothing: One of its most important uses. Applied in fire suits, steelmaking suits, high-temperature workwear, special combat uniforms, as well as heat resistant fabric for sewing into flame-retardant underwear, hoods, and gloves. It offers both fire protection and comfort.
- Transportation: In the automotive industry, it is used for engine compartment insulation, soundproofing of doors and windows, carpets, roofs, trunk liners, and seat covers. In aerospace, it is used in aircraft interior materials and combat uniforms.
- Industrial Applications: Includes high-temperature sealing packings, heat-resistant fabric for flame-retardant materials, brake preforms, and acid/alkali-resistant filter media. It is also used as welding spark protection sheets and asbestos replacement materials.
- Construction & Home Furnishing: For fabric flame retardant solutions such as insulation and soundproofing in high-temperature environments, hotel bed sheets, curtains, stage curtains, and furniture. It is also used as acoustic insulation filling in offices, hotels, factories, and homes.
- New Energy & Electronics: Used for insulation, friction, non-slip layers, heat resistant fabrics in fireproof materials, electronic sealing, sound absorption, and cushioning. Its antistatic and radiation-resistant properties are valuable in specialized electronic environments.
- Military & Safety: For tank crew uniforms, special combat uniforms, fire escape blankets, and fire extinguishing blankets.
Conclusion
As a high-performance heat-resistant fabric, pre-oxidized fiber knitted fabric (Panox knitted fabric) offers excellent flame resistance, reliable thermal stability, chemical durability, and user comfort. These features make it an ideal choice among modern flame retardant fabrics for a wide range of industrial applications and specialized protective uses.
