Author: [Bruce Zhou]
Affiliation: [Jota Machinery Composites Material Prepreg Solution]
Corresponding Author: [jotamachinery@gmail.com]
Published : December 04 , 2025
Abstract
Polyethylene (PE) has re-emerged as one of the most promising alternative precursors for low-cost carbon fiber (CF) manufacturing due to its high carbon content (~85.7 wt%), melt-spinnability, global availability, and potential to cut precursor cost by more than 50% relative to polyacrylonitrile (PAN). This paper synthesizes historical and contemporary research on PE-based carbon fiber production, focusing on precursor fiber manufacturing, sulfonation-driven stabilization, tension-controlled carbonization, resulting microstructure and mechanical properties, and recent industrialization attempts. The analysis reveals that PE-derived carbon fibers now routinely achieve tensile strengths of 1–2.5 GPa and moduli of 70–200 GPa, with values up to 2.4 GPa and 406 GPa demonstrated through boron catalysis. While PE offers lower environmental impact and reduced energy consumption, the stabilization (sulfonation) stage remains the central bottleneck due to acid handling, diffusion barriers, and process uniformity. Emerging approaches—including radiation-assisted stabilization, hybrid initiators, sheath–core precursors, and tailored polyolefins—point toward a scalable pathway for industrial deployment of PE-based carbon fibers in automotive, construction, and renewable-energy sectors.
1. Introduction
Conventional carbon fibers are produced overwhelmingly from polyacrylonitrile (PAN), which accounts for ~96% of global CF production. Despite unparalleled performance, PAN-based CF production remains cost-prohibitive, with ~50% of total cost originating from precursor manufacturing alone. To broaden carbon fiber adoption in high-volume sectors (automotive, wind energy, infrastructure), alternative precursors must be dramatically cheaper while still capable of producing mechanically competitive fibers.
Polyethylene (PE) is an attractive candidate for such next-generation precursors. As the world’s most widely produced polymer, PE is inexpensive (1.5–1.8 €/kg), melt-processable, and offers inherently high carbon content (~85.7 wt%). Highly oriented UHMWPE fibers can exceed 3–4 GPa tensile strength, suggesting that PE precursors possess the molecular alignment needed for strong carbon fibers. Recent advances in melt-spinning, sulfonation stabilization, and controlled-tension carbonization have enabled PE-derived carbon fibers with properties approaching commercial PAN-based products.
This paper provides a comprehensive technical evaluation of PE-based carbon fiber manufacturing, covering processing chemistry, mechanical behavior, challenges, and industry readiness.
2. Polyethylene as a Carbon Fiber Precursor
2.1 Advantages Over PAN and Pitch
PE offers several intrinsic advantages:
High Carbon Content & Yield
- PE: ~85.7% carbon, carbon yield 60–80%
- PAN: ~68% carbon, carbon yield 50–55%
- Pitch: ~90% carbon, carbon yield 60–80%
The yield advantage means significantly less mass loss and lower off-gas treatment requirements during carbonization.
Low Cost & Global Abundance
- PE resin: 1.5–1.8 €/kg
- PAN precursor: 3–7 €/kg
Melt spinning further reduces capital and energy costs by eliminating solvent recovery and coagulation systems.
Melt-Spinnability
PE can be melt-extruded into fine filaments, unlike PAN which requires wet-spinning. Melt spinning:
- avoids toxic solvents
- offers high throughput
- is compatible with large-tow production (≥10,000 filaments)
Mechanical Potential
Highly oriented PE fibers achieve:
- 1.5–4 GPa tensile strength
- 70–150 GPa modulus
Such alignment can be retained through controlled stabilization and carbonization.
3. Manufacturing PE Precursor Fibers
3.1 Melt Spinning
The industrially preferred process:
- PE pellets melted → extruded → air-quenched → cold-drawn.
- HDPE and LLDPE preferred due to linearity and high drawability.
- Fiber diameters of 7–12 μm are optimal for stabilization.
3.2 Gel Spinning
Used for UHMWPE (Dyneema, Spectra):
- produces extremely strong fibers (3–4 GPa)
- too expensive and complex for low-cost CF.
3.3 Requirements for PE Precursor Fibers
An optimal precursor must simultaneously possess:
- high axial orientation
- moderate crystallinity (to allow chemical diffusion)
- small diameter (~10 μm)
- low shrinkage tendency
- adequate tensile strength to withstand tension during stabilization.
Balancing orientation (for final properties) and amorphous content (for sulfonation) is a key scientific challenge.
4. Stabilization: Chemistry and Process Engineering
PE must be cross-linked before carbonization; otherwise it melts and degrades. Stabilization is therefore the pivotal step.
4.1 Why Stabilization is Needed
Unlike PAN (cyclizes in air), PE:
- has no functional groups for low-temperature cyclization
- melts at ~130°C
- would flow before forming carbon unless cross-linked.
Thus, stabilization converts PE from thermoplastic to infusible.
4.2 Stabilization Methods
Multiple methods exist, but sulfonation dominates due to efficiency and uniformity.
Chemical Routes
| Method | Strengths | Limitations |
|---|---|---|
| Sulfonation (H₂SO₄ or SO₃) | High crosslink density, scalable | Acid handling, equipment corrosion |
| Radiation (e-beam/gamma) | No chemicals, deep penetration | Cost, chain scission risk |
| Peroxide / Azo Crosslinking | Simple chemistry | Incomplete diffusion in fibers |
| Silane Grafting | Commercial XLPE analog | Moisture cure adds complexity |
| Oxidation | Simple | Occurs only at >300°C → fiber melts |
Among these, sulfonation yields the most consistent “infusible” fiber.
4.3 Sulfonation Chemistry
Sulfonation introduces:
- –SO₃H groups
- C=C conjugated polyenes
- inter- and intramolecular crosslinks
Mechanisms include:
- radical pathways (SO₃ abstracts hydrogen)
- electrophilic substitution (β-elimination to form double bonds)
- acid-radical routes (HSO₄• formation)
Key outcomes:
- mass gain 60–190%
- density increase
- elimination of crystalline melting peak (DSC)
- fiber darkening (brown → black)
4.4 Process Parameters
Critical parameters (from Table 9 of the 2022 review):
Temperature
- Begin <130°C
- Ramp to 150–180°C
- Higher temperatures accelerate sulfonation but risk uneven reaction.
Acid Concentration
- 93% H₂SO₄ required
- Water accumulation drastically reduces reactivity.
Time
- 1–4 hours typical for thin fibers
- Over-treatment → embrittlement
- Under-treatment → hollow “Pac-Man” cross-sections.
Tension Control
Stabilization must occur under controlled tension to:
- prevent shrinkage
- maintain molecular orientation
- avoid surface cracking or entanglement
Optimal tension eliminates entropic shrinkage without preventing chemical shrinkage.
5. Carbonization and Graphitization
After stabilization, PE fibers can be carbonized similarly to PAN fibers.
5.1 Carbonization Physics
- 200–600°C: SO₂, H₂O, CO₂ outgassing
- 600–1000°C: formation of turbostratic carbon
- 1000–2400°C: increased crystallite alignment
Tension During Carbonization
A decisive factor:
- prevents ~30% shrinkage
- improves modulus by up to an order of magnitude
- produces smoother surfaces → higher strength
Catalyzed Graphitization
Boron additives dramatically enhance ordering:
- Up to 406 GPa tensile modulus at 2400°C.
6. Mechanical Properties of PE-Derived Carbon Fibers
Representative Values (Literature 1978–2025)
| Precursor Type | Strength (GPa) | Modulus (GPa) | Notes |
|---|---|---|---|
| LLDPE CF | 0.3–2.1 | 20–150 | Easy stabilization |
| HDPE CF | 1.3–2.5 | 70–178 | Consistent performance |
| UHMWPE CF | 0.4–2.1 | 20–210 | High potential but hard to stabilize |
| Boron-Doped PE CF | 2.4 | 406 | Highest modulus reported |
These values approach those of commercial large-tow PAN CF used in automotive and industrial applications.
7. Surface Chemistry and Composite Adhesion
PE-based CFs:
- are nearly pure carbon
- lack inherent nitrogen/oxygen groups
- require surface oxidation for good epoxy adhesion
- are compatible with standard fiber sizings
Surface morphology depends heavily on controlled tension during stabilization/carbonization.
8. Industrialization Challenges and Scalability
8.1 Precursor Production
Recent breakthroughs:
- 10,000-filament melt-spun PE tows (Aramco/ITA, 2025)
- challenges remain with quench uniformity and multi-filament consistency
8.2 Continuous Sulfonation Lines
Industrial requirements:
- acid recirculation
- high-temperature corrosion-resistant reactors
- tensioning systems capable of ±1% strain control
- SO₂ off-gas capture and acid regeneration
Stabilization accounts for up to 36% of PE-CF cost—currently the largest contributor.
8.3 Cost Projections
Studies suggest:
- PAN-CF cost: 14 €/kg
- PE-CF potential cost: 7–10 €/kg
- ≈50% reduction driven by cheaper precursor and simpler spinning
9. Sustainability and Life-Cycle Impact
Energy and Emissions
- PE-CF cumulative energy demand: 575 MJ/kg
- PAN-CF: 926 MJ/kg
- GWP: 21 kg CO₂/kg (PE-CF) vs. 39 kg CO₂/kg (PAN-CF)
Bio-Based Precursors
Bio-ethylene → bio-PE → bio-CF pathway offers substantial decarbonization potential.
10. Future Directions
10.1 Tailored Polyethylene Polymers
- co-monomers for easier crosslinking
- built-in unsaturation
- sheath–core PE structures
10.2 Alternative Stabilization
- electron-beam crosslinking
- hybrid UV–chemical routes
- additive-enhanced stabilization (bromine, boron, co-agents)
10.3 Advanced Carbonization Strategies
- optimized tension profiles
- staged carbonization for controlled SO₂ evolution
- low-temperature graphitization catalysts
10.4 Application Expansion
- automotive structural parts
- wind turbine blades
- hydrogen tanks (with hybrid CF)
- low-cost building reinforcement
11. Conclusions
Polyethylene is one of the most promising alternative precursors for low-cost, sustainable carbon fibers. Its advantages—high carbon content, low cost, melt-processability, and scalable sourcing—align with global demand for mass-market carbon fiber applications. Technical progress over the past decade demonstrates that PE-derived carbon fibers can reach mechanical properties near those of commodity PAN-based fibers, especially when tension-controlled stabilization and carbonization are implemented.
The primary barrier remains sulfonation stabilization, which must be optimized for speed, uniformity, and industrial safety. Emerging radiation-assisted and hybrid stabilization strategies indicate realistic pathways to high-volume production. With continued R&D, PE-based carbon fibers could reshape the economics of the CF industry and expand composite adoption across mobility, energy, and infrastructure sectors.