PBO (Zylon) HM
Grade
also Zylon
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.
Values for the HM condition
Other PBO (Zylon) grades and fills
PBO (Zylon) is listed in 3 conditions; see the grade overview at PBO (Zylon).
Compare all 3 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
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 | — |
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 | — |
HMThis page 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 | — |
What is PBO (Zylon) HM?
PBO (Zylon) HM is PBO (Zylon) in the HM grade — heat-treated yarn with ~50 % higher modulus and lower moisture regain; pick it for stiffness-critical composites, tethers, tension members and dimensionally stable structures. PBO (Zylon) HM has a tensile strength of 5,800 MPa (841 ksi), stronger than 98% of composite grades. Elongation at break is 2.5% and the elastic modulus is 270 GPa (39.2 Msi). PBO (Zylon) HM has a density of 1.56 g/cm³ (0.0564 lb/in³), lighter than 55% of composite grades. Its glass-transition temperature is 500°C (932 °F).
Advantages
- Stiff — 270 GPa (39.2 Msi), better than 89% of composite grades
Limitations
- Degrades in UV without stabilisers — 12/100, worse than 100% of composite grades
- Difficult to machine — 12/100, worse than 89% of composite grades
- High embodied carbon — 30 kg CO₂/kg, worse than 80% of composite grades
PBO (Zylon) HM properties
Typical room-temperature values for PBO (Zylon) HM; 16 are specific to this condition. Other listed values are PBO (Zylon) reference data and may not represent this condition. Bars are the position among composite grades.
Physical4
PBO (Zylon) HM has a density of 1.56 g/cm³ (0.0564 lb/in³), lighter than 55% of composite grades. Its glass-transition temperature is 500°C (932 °F).
Mechanical4
PBO (Zylon) HM has a tensile strength of 5,800 MPa (841 ksi), stronger than 98% of composite grades. Elongation at break is 2.5% and the elastic modulus is 270 GPa (39.2 Msi).
Thermal7
PBO (Zylon) HM is rated for continuous service to 310°C (590 °F). Thermal expansion is -6 µm/m·K (-3.33 µin/in·°F).
Electrical1
Chemical & Environmental3
Corrosion resistance is very good (70/100), worse than 64% of composite grades. UV resistance is not recommended.
Sustainability3
Producing a kilogram of PBO (Zylon) HM takes about 500 MJ of energy and emits 30 kg of CO₂ — more than 84% of composite grades. Typical recycled content is 0%.
Manufacturability1
PBO (Zylon) HM's machinability is not recommended (12/100, worse than 89% of composite grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with PBO (Zylon) HM
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.
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.
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 | — |
PBO (Zylon) HM — frequently asked
What is PBO (Zylon) HM used for?
PBO (Zylon) HM 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) HM?
PBO (Zylon) HM 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.
Is PBO (Zylon) HM easy to machine?
Not especially — machinability is rated not recommended (12/100, worse than 89% of composite grades). 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) HM be welded?
Not weldable; join by stitching with PBO/aramid thread, mechanical clamping or adhesive bonding of the composite laminate.
What surface finishes work on PBO (Zylon) HM?
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.
Can PBO (Zylon) HM 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.
What is the maximum service temperature of PBO (Zylon) HM?
PBO (Zylon) HM is rated for continuous use to about 310°C (590 °F), and briefly to 550°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- Zylon (PBO fiber) Technical Information — Toyobo Co., Ltd. (2020)
- ASM Handbook Vol. 21: Composites — High-performance organic fibers — ASM International (2001)
- NIJ/NIST studies on aging of PBO body-armor fiber — NIST (2005)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.