PBO fiber is a super fiber made from poly(p-phenylene-2,6-benzobisoxazole) polymer through a dry-jet wet spinning process. Its molecular structure possesses high rigidity and orientation, which endows it with unparalleled mechanical properties and thermal stability. PBO fibers are mainly divided into two types: one is as-spun (AS type), obtained directly through spinning; the other is high-modulus (HM type), which is the as-spun fiber after heat treatment, possessing a higher modulus.
Weaving refers to the traditional process of interlacing two sets of yarns (warp and weft) at right angles to form a fabric. PBO woven fabric is a fabric produced using PBO fiber as the raw material through the weaving process. It usually adopts a plain weave structure, the simplest interlacing method where each weft yarn alternately passes over and under the warp yarns, providing good structural stability and mechanical properties.
The production of PBO woven fabric is a precise process, mainly including three major steps: fiber preparation, yarn preparation, and weaving.
PBO polymer is synthesized through a polycondensation reaction between terephthalic acid or terephthaloyl chloride and 4,6-diamino-1,3-benzenediol hydrochloride (DAR) in a solvent such as polyphosphoric acid (PPA). The resulting polymer solution is spun into fibers via a dry-jet wet spinning (air-gap spinning) process. In this process, the liquid crystal solution is extruded from the spinneret, first passes through an air layer (dry section) where high orientation and stretching occur, and then enters a coagulation bath (wet section) for solidification. This process minimizes defects on the fiber surface, thereby enhancing its mechanical properties.
The yarn preparation before weaving PBO fabric and the weaving itself have specific requirements:
Key steps include:
The following is a schematic diagram of the PBO woven fabric manufacturing process:
The performance of PBO woven fabric is exceptional. Its main technical parameters are shown in the table below:
| Property | Parameter Indicators | Comparative Reference (e.g., Para-aramid) |
|---|---|---|
| Fiber Linear Density | Various specifications from 100D - 1500D | Similar common specifications |
| Tensile Strength | 30 - 38 cN/dtex | About twice that of para-aramid |
| Tensile Modulus | 140 - 280 GPa | About twice that of para-aramid |
| Elongation at Break | 2% - 4% | Relatively low |
| Density | 1.54 - 1.56 g/cm³ | Much lighter than steel wire (~7.8 g/cm³) |
| Heat Resistance | Thermal decomposition temperature ~650℃ Isothermal mass loss in air at 400℃ <5% |
About 100℃ higher than aramid |
| Limiting Oxygen Index (LOI) | 68 | Extremely high (aramid is about 29) |
| Long-Term Heat Resistance | Plastic deformation <0.03% after 100 hours under 50% of breaking load | Excellent |
| Chemical Stability | Resistant to most organic solvents and alkalis Easily dissolved by strong acids like conc. sulfuric acid, methanesulfonic acid |
Better than aramid (aramid is sensitive to bleach) |
Besides the above parameters, PBO fiber also possesses excellent impact resistance, fatigue resistance, friction resistance, and dimensional stability (coefficient of thermal expansion is -6×10⁻⁶/℃). Its dielectric constant is low, offering good wave transmission properties, making it suitable for electromagnetic window applications like radomes.
Thanks to its outstanding performance, the applications of PBO woven fabric are mainly concentrated in high-tech and high-end industrial fields:
PBO woven fabric represents the pinnacle of modern textile materials and technology. Its comprehensive performance far exceeds that of traditional high-performance fibers like aramid and ultra-high molecular weight polyethylene. Manufactured through sophisticated processes of polymerization, dry-jet wet spinning, twisting, and weaving, it possesses unparalleled strength, modulus, heat resistance, and flame retardancy.
Although the current cost of PBO fiber is high and its stability in strong acid environments is insufficient, its application value in fields such as aerospace, national defense, fire protection, and high-end industry is irreplaceable. With the continuous maturation of production technology and expansion of production capacity, the cost of PBO materials is expected to gradually decrease, and its application fields will further expand. It is anticipated to play a significant role in more areas such as new energy vehicles and special building reinforcement in the future.
