PBO (Zylon): Properties, Grades & Uses

PBO (Zylon) grades and fills

PBO (Zylon) is supplied in 3 conditions, soft to hard.

Compare all 3 grades and fillsHide

Grade · open for datasheet	Best for	Tensile MPa	Elong. %
UD-EP Unidirectional PBO/epoxy laminate	PBO-reinforced epoxy prepreg/laminate for lightweight pressure-vessel overwrap, stiffeners and impact structures; excellent tensile properties but very low compressive and off-axis strength.	2,600	1.8
FAB Woven PBO fabric / ballistic and cut-resistant cloth	Plain or basket-weave fabric from AS yarn for soft armour, blast blankets, welding curtains and heat-resistant conveyor covers; fabric strengths are per-yarn values derated by crimp.	3,500	4
HM High-modulus heat-treated PBO filament yarn	Heat-treated yarn with ~50 % higher modulus and lower moisture regain; pick it for stiffness-critical composites, tethers, tension members and dimensionally stable structures.	5,800	2.5

Supply forms, finishes and certifications

Ways PBO (Zylon) is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.

Option	What it is	Type
ASDefault	As-spun standard-modulus PBO filament yarn	Coating

What is PBO (Zylon)?

PBO (Zylon) is a poly(p-phenylene benzobisoxazole) liquid-crystalline fiber, the strongest and stiffest organic fiber in commercial production, supplied as AS and HM yarn, woven fabric and unidirectional epoxy prepreg. Engineers choose it where para-aramid strength is insufficient: 5800 MPa tensile strength and 180 GPa modulus at 1.54 g/cm3, 3.5% elongation and service to 300 C. It degrades on exposure to light and humidity, so parts require UV-opaque covers or coatings, and cost and availability are far worse than aramid. Where long-term aging resistance matters more than peak strength, para-aramid or UHMWPE fiber is the usual substitute. PBO (Zylon) has a density of 1.54 g/cm³ (0.0556 lb/in³), lighter than 58% of composite grades. Its glass-transition temperature is 500°C (932 °F). PBO (Zylon) has a tensile strength of 5,800 MPa (841 ksi), stronger than 98% of composite grades. Elongation at break is 3.5% and the elastic modulus is 180 GPa (26.1 Msi).

What is PBO (Zylon) used for?

high-performance ballistic armor
aerospace tethers/cables
sporting goods
reinforcement for extreme-performance composites

Advantages

Ductile — tolerates forming and impact — 3.5%, better than 78% of composite grades
Stiff — 180 GPa (26.1 Msi), better than 76% of composite grades

Limitations

Degrades in UV without stabilisers — 12/100, worse than 100% of composite grades
Absorbs moisture — dry before molding — 2%, worse than 88% of composite grades
Difficult to machine — 15/100, worse than 84% of composite grades
High embodied carbon — 30 kg CO₂/kg, worse than 80% of composite grades

PBO (Zylon) properties

Typical room-temperature values; bars are the position among composite grades.

Physical4

PBO (Zylon) has a density of 1.54 g/cm³ (0.0556 lb/in³), lighter than 58% of composite grades. Its glass-transition temperature is 500°C (932 °F).

Density1.54 g/cm³0.06 lb/in³

Glass Transition (Tg)500°C932 °F

Water Absorption (24 h)2%

Water Absorption (Saturation)2.5%

Mechanical4

PBO (Zylon) has a tensile strength of 5,800 MPa (841 ksi), stronger than 98% of composite grades. Elongation at break is 3.5% and the elastic modulus is 180 GPa (26.1 Msi).

Elastic (Young's) Modulus180 GPa26.1 Msi

Tensile Strength (Ultimate)5,800 MPa841 ksi

Elongation at Break3.5%

Compressive Strength300 MPa43.5 ksi

Thermal7

PBO (Zylon) is rated for continuous service to 300°C (572 °F). Thermal expansion is -6 µm/m·K (-3.33 µin/in·°F).

Specific Heat Capacity1,200 J/kg·K0.29 BTU/lb·°F

Thermal Expansion (CTE, 20–100 °C)-6 µm/m·K-3.3 µin/in·°F

Max Service Temperature (continuous)300°C572 °F

Min Service Temperature-196°C-321 °F

Flammability (UL 94)V-0 equivalent behaviour; fabric does not sustain burning in air (LOI ≈68 %)

Limiting Oxygen Index68%

Max Service Temperature (short-term)550°C1,022 °F

Electrical1

Volume Resistivity1×10¹⁴ Ω·cm

Chemical & Environmental3

Corrosion resistance is very good (70/100), worse than 64% of composite grades. UV resistance is not recommended.

Corrosion ResistanceVery good70/100

UV / Weathering ResistanceNot recommended12/100

Chemical Resistance SummaryExcellent against organic solvents, fuels and most alkalis; resistant to abrasion and cut. Degraded by concentrated sulfuric/nitric/methanesulfonic acids, by prolonged UV/visible light, and by hydrolysis in hot humid environments (strength loss over months of service).

Sustainability3

Producing a kilogram of PBO (Zylon) takes about 500 MJ of energy and emits 30 kg of CO₂ — more than 84% of composite grades. Typical recycled content is 0%.

Embodied Energy (primary production)500 MJ/kg214,962 BTU/lb

Embodied Carbon (primary production)30 kg CO₂/kg

Typical Recycled Content0%

Manufacturability1

PBO (Zylon)'s machinability is poor (15/100, worse than 84% of composite grades).

MachinabilityPoor15/100

Common Calculations2

Specific Strength (UTS / density)calculated3,766 kN·m/kg

Specific Stiffness (E / density)calculated116.9 MN·m/kg

Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.

Strength versus weight in the composite family

Yield strength against density for every composite grade FabDigit runs. PBO (Zylon) is highlighted; hover a dot for its name, or open the interactive family chart.

Working with PBO (Zylon)

Is PBO (Zylon) easy to machine?

Fabric and laminates cannot be sheared cleanly — use hot knife, ultrasonic cutter, waterjet or new carbide/PCD tooling; fibers fuzz and blunt tools quickly.

Can PBO (Zylon) be welded?

Not weldable; join by stitching with PBO/aramid thread, mechanical clamping or adhesive bonding of the composite laminate.

Can PBO (Zylon) be formed, bent or molded?

Processed as continuous yarn — weaving, braiding, filament winding or prepreg lay-up with epoxy/phenolic; cure below ~180 °C and avoid moisture pick-up before cure.

PBO (Zylon) chemical composition (wt %)

Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.

Element	Spec limit (wt %)	Nominal
residual phosphorus (from PPA solvent)Residual acid content is a key driver of hydrolytic aging	0.05 – 0.6	0.3
finish / sizingSpin finish on yarn surface	0.2 – 1	0.5
poly(p-phenylene-2,6-benzobisoxazole) reRigid-rod heterocyclic polymer; monomers 4,6-diaminoresorcinol dihydrochloride + terephthalic acid, dry-jet wet spun from polyphosphoric acid	balance

What surface finishes work on PBO (Zylon)?

Surface treatment (plasma, epoxy sizing) needed for resin adhesion; protect all exposed parts with UV-opaque covers, coatings or outer fabric layers to limit light and humidity aging.

Equivalent designations

Standards and trade names that resolve to PBO (Zylon) in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.

Trade names: Zylon
Also called: PBO

Other Aramid & specialty reinforcements composite grades

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Compare PBO (Zylon) with…

Benchmark PBO (Zylon) against the top 3 neighbours

How much does PBO (Zylon) cost?

PBO (Zylon) is a high-cost composite ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.

PBO (Zylon) — frequently asked

What is PBO (Zylon) used for?

PBO (Zylon) is typically used for high-performance ballistic armor, aerospace tethers/cables, sporting goods and reinforcement for extreme-performance composites. In short: strongest organic fiber; higher modulus than aramid; light and humidity sensitive.

What is the tensile strength of PBO (Zylon)?

PBO (Zylon) has a typical tensile strength of 5,800 MPa (841 ksi) — stronger than 98% of composite grades. Strength varies by condition: see the 3 listed tempers.