PBO Fiber (ZYLON®)

What is PBO (ZYLON®)?


ZYLON® consists of rigid rod chain molecules of poly(p-phenylene-2, 6-benzobisoxazole)(PBO).

A poly-p-phenylenebenzobisoxazole (PBO) fiber Toyobo developed and put on the market in 1998. It is the world’s strongest PBO fiber with the highest flame resistance. Among existing organic fibers, PBO has world-leading levels of strength, tensile modulus and heat resistance. The product’s many applications include rope and cable, heat-resistant materials and racing car bodies

Chemical structure of ZYLON®

ZYLON® Fiber Property

ZYLON®(PBO fiber) is the next generation super fiber with strength and modulus almost doubles that of p-Aramid fiber. ZYLON® shows 100℃ higher decomposition temperature than p-Aramid fiber. The limiting oxygen index is 68, which is the highest among organic super fibers. There are two types of fibers, AS (as spun) and HM (high modulus). HM is different fromAS in modulus, moisture regain and etc.

Type AS (Regular) HM (High Modulus)
Filament Decitex (dtex) 1.7 1.7
Density (g/cm³) 1.54 1.56
Moisture Regain (65% RH) (%) 2.0 0.6
Tensile Strength (cN/dtex) 37 37
(GPa) 5.8 5.8
(KSI) 840 840
Tensile Modulus (cN/dtex) 1150 1720
(GPa) 180 270
(KSI) 26 39
Elongation at Break (%) 3.5 2.5
Melting Temperature (℃) none none
Decomposition Temperature in Air (℃) 650 650
Coefficient of Thermal Expansion (ppm/℃) -6
Limiting Oxygen Index 68 68
Dielectric Constant at 100kHz 3.0
Dissipation Factor 0.001

Mechanical Property

Tensile Strength and Modulus

Zylon® fiber has superior tensile strength and modulus to p-Aramid fiber.

Flame Resistance and Thermal stability

Zylon® fiber has outstanding flame resistance and thermal stability among organic fibers.

Creep Properties

Creep Properties ZYLON® has superior creep resistance to p-Aramid fibers. (Creep means a non-recoverable strain after prolonged static loading.) When a certain load is applied to yarn, recoverable strain (initial strain) and non-recoverable strain are observed. For ZYLON® HM, non-recoverable strain after 100 hours under 50% of breaking load (Safety factor (SF)=2) is less than 0.03%.

Creep Parameter

Creep Parameter Creep parameters (slope of straight line in above figure) are compared with p-Aramid fibers. ZYLON® shows less than half of creep parameter of p-Aramid fiber. Creep strain is measured under 50% of the breaking load for each fiber. Note that the actual load applied to ZYLON® is almost double that of p-Aramid fiber.

Creep parameter under 50% of breaking strength

Zylon AS Zylon HM p-Aramid p-Aramid HM
3.2×10-4 1.1×10-4 5.0×10-4 2.5×10-4

*Time to failure

After a certain loading time, yarn breakage may occur. The above figure shows the relationship between time to failure and applied load level (ZYLON®HM). Based on the extrapolation, 107 minutes (19 years) of time to failure can be estimated under 60% of the breaking strength。。

Abrasion Resistance between fiber and metal

Abrasion resistance between fiber and metal Abrasion resistance of ZYLON® is higher than p-Aramid fiber under the same load, but much lower than Nylon or high molecular weight polyethylene fiber.

Light resistance

The strength of ZYLON® decreases with exposure to sunlight. Light resistance of ZYLON® was evaluated using Xenon light weather-ometer. As shown below, the strength decreases sharply at the initial stage of exposure. End products of ZYLON for outdoor use have to be protected by covering materials. The residual strength of ZYLON® after 6 months exposure to daylight is about 35%.

ZYLON® should be protected not only from ultraviolet light but also from visible light. These data show strength retention after exposure to fluorescent lamp.

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Comparison with Other High-performance Fibers

ZYLON® has the highest tensile strength and tensile modulus among high-performance fibers.

  Tensile Strength Tensile Modulus Elongation at Break Density Moisture Regain LoI Heat Resistance*
cN/dtex g/d GPa cN/dtex g/d GPa % g/cm³ %
ZYLON-AS 37 42 5.8 1150 1300 180 3.5 1.54 2.0 68 650
ZYLON-HM 37 42 5.8 1720 2000 270 2.5 1.56 0.6 68 650
p-Aramid 19 22 2.8 750 850 109 2.4 1.45 4.5 29 550
m-Aramid 4.7 5.3 0.65 124 140 17 22 1.38 4.5 29 400
Steel Fiber 3.5 4 2.8 260 290 200 1.4 7.8 0
Carbon Fiber 20 23 3.5 1310 1480 230 1.5 1.76
PBI 2.7 3.1 0.4 40 45 5.6 30 1.4 15 41 550
Polyester 8 9 1.1 110 125 15 25 1.38 0.4 17 260

* Melting or Decomposition

With its wide range of product lineups from staple fibers all the way to composite products, we aim to meet various needs for high-intensity applications. ZYLON® is developed to improve, enhance, and protect—across industries and around the world.

Product Lineups

Staple Fiber AS HM

Cut Length (mm) 4476
Chopped Fiber AS HM

Cut Length (mm) 136 136
Spun Yarn AS HM

Yarn Count (Na) 20/120/230/1
(Nm) 34/134/251/1
Filament AS HM

Linear Density (dtex) 16527855511101670 273545109016403270
Filaments 99166332664996 1663326649961992
Cylindrical Bobbin Innerdiameter (mm) 94 94
Cylindrical bobbin Length (mm) 216 216
Woven Fabric LZY3011 LZY0530W LZY0535W LZY0242W LZY0160W LZY0140W LZY1618 LZY1613
Fiber Type AS1670dtex×2 AS555dtex AS555dtex AS278dtex AS110dtex AS165dtex HM1640dtex HM1640dtex
Weaving Structure Plain Plain Plain Plain Plain Plain Plain Plain
Width (m) × Length (m) 1.1 × 100 1.2 × 100 1.2 × 100 1.2 × 100 1.0 × 100 1.0 × 100 1.0 × 100 1.0 × 100
Density (yarns/inch) Warp 11±1 30±2 35±2 42±2 60±3 40±2 18±2 13±1
Fill 10±1 30±2 35±2 42±2 60±3 40±2 18±2 13±1
Weight (g/m2) 280±20 135±10 160±15 96±6 54±3 54±3 230±20 170±15
Thickness (mm) 0.60±0.10 0.20±0.05 0.25±0.05 0.15±0.03 0.08±0.02 0.08±0.02 0.40±0.15 0.23±0.05
Under Development
Available to offer sample products



ZYLON® fiber composite reinforcements offer effective solutions for the rigorous and competitive requirements of sports and recreational activities. Our products elevate athletic equipment performance and durability, while also decreasing weight compared to traditional materials.

Bicycle Spokes and Tire Reinforcements

Yacht Ropes


Racing Cars

Sporting Goods Composites

Industrial Materials

ZYLON® fiber enhances durability and structural integrity, allowing users to engineer solutions for heavy duty applications. Combining heat resistance and high modulus, ZYLON® outperforms similar organic fibers in many key properties and is built for extended use.

Heat Resistant Felt

Cable Cover for Welding

Cable Tension Member

Cement Reinforcement


For nearly 30 years, ZYLON® has been a fiber of choice for a variety of space exploration and specialty aerospace applications.  Its weight to strength ratio, low deformation rate, and high LOI put ZYLON® on the short list of technologies capable of meeting specific outer space and high-altitude engineering requirements.

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