Challenges of producing carbon fiber yarns due to high costs

Spinners face numerous challenges while producing carbon fiber (CF) yarns, primarily due to the overall high production cost of the material. While spinning is a key step, the cost drivers extend across the entire manufacturing chain.

Here are the main challenges and how to  deal with them.

Issues for spinners

The high cost of carbon fiber yarn is a cumulative result of several factors, with the initial and subsequent thermal processes being the most critical:

1. High cost of precursor material

• Challenge: The main precursor, polyacrylonitrile (PAN), accounts for the largest share of the final carbon fiber cost (often over 50 per cent). High-performance PAN requires extremely pure and precisely aligned molecular chains, which makes its synthesis expensive.
• Spinning impact: The quality and type of the precursor fiber directly influence the subsequent spinning and thermal processes. Defects in the precursor can lead to fiber breakage or low mechanical properties in the final carbon fiber, forcing manufacturers to use more costly, higher-grade raw materials to ensure product integrity.

2. Capital-intensive equipment and infrastructure

• Challenge: The machinery for carbon fiber production, including the spinning machines and, more significantly, the oxidation ovens and carbonization furnaces, requires substantial capital investment. These furnaces operate at incredibly high temperatures ($1,000^{\circ} \text{C}$ to $3,000^{\circ} \text{C}$) and require precise atmospheric and tension control.
• Spinning impact: The need for highly controlled spinning environments (e.g., in wet or dry-jet wet spinning) and specialized, high-capacity equipment contributes heavily to the total initial investment and subsequent depreciation costs.

3. Energy-intensive thermal processes

• Challenge: The post-spinning steps - stabilization (oxidation) and carbonization - are extremely energy-intensive. The prolonged heating process consumes enormous amounts of electricity and natural gas, significantly driving up the operating costs.
• Spinning impact: While spinning itself is less energy-intensive than carbonization, it determines the initial fiber structure. A poor or thick fiber structure can prolong the stabilization time, thereby increasing overall energy consumption and cost.

4. Low material yield and waste generation

• Challenge: The conversion process from the PAN precursor fiber to the final carbon fiber is inefficient, with a low material yield (e.g., 3 tons of PAN to 1 ton of CF). The intense heat removes non-carbon atoms as volatile gases, and process variations can lead to scrap fiber.
• Spinning impact: Poor control over the spinning parameters (e.g., molecular alignment, fiber thickness, or defects) can result in a higher rate of material loss during the subsequent heating steps.

Ways to deal with these challenges

Strategies to reduce costs focus on all stages, from the precursor material to process efficiency:

1. Optimize precursor and spinning technology

Utilize low-cost precursors: Replace high-cost PAN with more affordable alternatives like lignin (a byproduct of the paper industry) or petroleum pitch. A low-cost precursor can directly cut the material cost, which is the largest component of the final price.

Increase tow size: Using precursor tows with a larger number of filaments (e.g., 48K or 50K instead of 3K or 12K) significantly reduces the cost per kilogram of the final carbon fiber. This strategy allows the use of the same processing equipment (spinning head, furnace) to produce a greater volume of material, leveraging economies of scale.

Process optimization (Spinning speed): Develop new spinning techniques, such as improvements in dry-jet wet spinning, to increase the speed at which precursor fibers are produced. Higher spinning line speeds boost throughput, which reduces the labor and depreciation costs allocated to each kilogram of yarn.

Improve process efficiency and energy use

Use novel oxidation techniques: Since the stabilization/oxidation step is long and energy-consuming, new methods like plasma treatment or microwave-assisted carbonization are being explored. These techniques aim to achieve stabilization faster and at lower temperatures, directly reducing the overall energy bill.

Enhanced tension and temperature control: Implementing precise, real-time control systems for temperature and tension in the thermal processes prevents defects like filament breakage and micro-cracks. This improves the final yield by minimizing scrapped batches, making the capital and energy investment more productive.

3. Focus on recycling and circularity

Carbon fiber recycling: Developing efficient and scalable methods like pyrolysis or solvolysis to recover carbon fibers from end-of-life composite parts. Recycled carbon fiber (rCF) is significantly cheaper than virgin fiber, providing a lower-cost input material for certain