Length Specifications and Applicability of Chopped Carbon Fiber
A brief introduction to the length specifications and applicability of chopped carbon fiber.
Length Specifications and Applicability of Chopped Carbon Fiber
Chopped carbon fiber refers to carbon fiber filaments that have been cut into short fibers of a specific length; these serve as reinforcing materials in fields such as plastics, rubber, coatings, and cement-based composites. The specific length specification directly influences the material's dispersibility, reinforcing efficacy, and processing adaptability. The 3mm, 6mm, and 12mm lengths are the three most common specifications.
Basic Concepts
Chopped carbon fiber is produced by cutting carbon fiber filaments (typically ranging from 1K to 48K tow sizes) to a precise length using a cutting machine; the resulting lengths generally range from 1mm to 50mm. After cutting, the fibers retain their original diameter (typically 5–8 μm) and mechanical properties, though their aspect ratio (the ratio of length to diameter) varies according to the fiber length.
The Importance of Aspect Ratio:
A higher aspect ratio results in a more pronounced reinforcing effect.
An excessively high aspect ratio increases the difficulty of achieving uniform dispersion.
An excessively low aspect ratio diminishes the reinforcing effect.
Based on a fiber diameter of 7 μm, the aspect ratios for different lengths are as follows:
3mm: Approximately 430
6mm: Approximately 860
12mm: Approximately 1,710
Characteristics of the Three Specifications
3mm Chopped Carbon Fiber
Aspect ratio of approximately 430; exhibits excellent flowability and is easy to disperse.
Yields products with smooth surface finishes and offers a wide processing window.
The reinforcing effect primarily focuses on crack resistance and abrasion resistance, with limited improvement in overall tensile strength.
Applications: Injection molding, extrusion, 3D printing, coatings.
6mm Chopped Carbon Fiber
Aspect ratio of approximately 860; strikes an optimal balance between dispersibility and reinforcing efficacy.
Offers the best cost-performance ratio and enjoys the widest range of applications.
Retains a residual length of approximately 0.3–0.6mm after injection molding.
Applications: Injection molding, reinforcement of Nylon/PP/PEEK, automotive functional components.
12mm Chopped Carbon Fiber
Aspect ratio of approximately 1,710; delivers a highly significant reinforcing effect.
Dispersion is more challenging, placing high demands on processing equipment and techniques.
The surface of the finished product may exhibit a visible fiber texture.
Applications: Compression molding, LFT (Long Fiber Thermoplastics), construction mortars, high-end structural components.
The Relationship Between Length and Performance
Length | Reinforcement Effect | Processability | Surface Quality | Cost |
3mm | Moderate | Excellent | Excellent | Low |
6mm | Good | Good | Good | Moderate |
12mm | Significant | Fair | Fair | Higher |
Selection Based on Substrate
Substrate Type | Recommended Length | Rationale |
Injection Molding Plastics | Predominantly 6 mm | Balances reinforcement with flowability |
Extrusion Plastics | 3-6mm | High flowability requirements |
Paints/Coatings | 1-3mm | Ensures a smooth surface finish |
Mortar/Concrete | 3-6mm | Crack resistance and good dispersion |
BMC Molding Compounds | 6-12mm | Moderate flowability during molding |
Dedicated LFT Applications | 12-24mm | Preserves long-fiber reinforcement |
Selection Considerations
By Process: Injection molding - 6mm; Extrusion/Coating - 3mm; Compression molding - 6-12mm
By Reinforcement Needs: General reinforcement - 6mm; Ultimate reinforcement - 12mm
By Surface Requirements: High surface quality - 3mm
By Cost: 3mm and 6mm offer the best cost-performance ratio; 12mm is more expensive.
Summary
3mm, 6mm, and 12mm constitute the core length spectrum of chopped carbon fiber, corresponding to three different application positions: high flowability, comprehensive balance, and significant reinforcement. 3mm is suitable for high flowability and surface requirements, 6mm is a general balance choice, and 12mm is used for high-performance needs. Selection requires comprehensive consideration of processing technology, reinforcement effect, and cost factors. We are a Chinese carbon fiber material manufacturer. For more information, please contact us via email at annayu@169chem.net or WhatsApp at +8618909016373.