The two core issues in the procurement of chopped carbon fibers 

Short-cut carbon fibers are widely used in enhancing thermoplastic or thermosetting plastics (such as nylon, polypropylene, epoxy resin, etc.), conductive materials, and wear-resistant components, etc. Many purchasers often encounter confusion when selecting types: Even though they are all called Short-cut carbon fibers, why are some mixed materials not evenly dispersed, and why are there severe floating fibers on the surface of some products? Below, starting from two common issues, we will help you clarify your thinking. 

1. Length and Dispersion: How to balance the enhancement effect and processability? 

The length of the chopped carbon fibers directly determines the reinforcing effect, but it also affects the uniformity of dispersion within the matrix. 

Length selection: When used in injection molding processes, a common specification range is 6-12mm. Within this range, carbon fibers can be uniformly mixed with plastic particles in the twin-screw extruder, and they are less likely to be excessively broken when passing through the screw of the injection molding machine. They can retain a certain length in the final product to provide an enhanced effect. For molding or extrusion processes, a specification of 12mm or above can be chosen, allowing for longer fiber retention and a more significant enhancement effect. 

Dispersion risk: Carbon fibers with excessively long lengths are prone to agglomeration during injection molding or extrusion processes, resulting in uneven dispersion and the appearance of floating fibers or rough surfaces on the product. Additionally, overly long fibers are more likely to break in the screw, thereby undermining the original "long-fiber reinforcement" advantage. When purchasing, you can inform the supplier of your processing method (injection molding, compression molding, extrusion, etc.) to ensure the selection of appropriate length specifications. 

II. Stabilizer: Why does the same carbon fiber work well when used in nylon but not when used in polypropylene? 

The sizing agent is a coating applied to the surface of carbon fibers, its function being to protect the fibers and enhance the bonding strength between the fibers and the matrix resin. Incompatibility between the type of sizing agent and the matrix material is a common cause of poor performance of composite materials. 

Matching base material: Different resin systems (such as nylon, polypropylene, epoxy, polycarbonate, etc.) require carbon fibers with corresponding adhesives. The carbon fiber sizing agent for nylon needs to have good compatibility with nylon, while the one for polypropylene needs to have compatibility with polypropylene. If the sizing agent does not match the base material, the interfacial bonding force between the fiber and the resin will be weak, and stress cannot be effectively transmitted, resulting in a significant reduction in the enhancement effect. 

Starch content: The starch content (including the glue content) also needs to be moderate. If the content is too low, the fibers are prone to fraying and breaking during processing; if it is too high, it may affect the direct bonding of the fibers and the resin. When purchasing, you can inquire with the supplier whether the type of starch used has been optimized for your base material. 

Summary and Selection Suggestions 

When purchasing short-cut carbon fibers, the following steps are recommended for confirmation: 

First, consider the process, then determine the length: For injection molding, the thickness can be 6-12mm; for compression molding or extrusion, it can be 12mm or more. 

Identify the substrate and match the sizing agent: Inform the supplier of your resin type (nylon, polypropylene, epoxy, etc.) so that the corresponding sizing agent can be matched. 

Actual measurement on the sample machine: Conduct a small-scale trial on your production line to observe whether the uniformity of the mixture, the surface quality of the product, and the mechanical properties meet the standards. 

Yancheng Xiangsheng Carbon Fiber Technology Co., Ltd. specializes in the production and research of short-cut carbon fibers and carbon fiber powders. We can customize the length specifications and sizing agents according to your process requirements. Please feel free to request samples for testing and communicate technical requirements.