Cutting-edge Carbon Fiber Procurement Guide: Practical Steps from Selection to Inspection 

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. For products of different specifications, how to efficiently complete the selection and procurement? Below, we will outline several key steps for you. 

Step 1: Define the purpose and determine the specifications 

The performance requirements for chopped carbon fibers vary depending on the application. Before making a purchase, it is advisable to confirm the following information, as it will help the supplier recommend suitable products. 

Determine the type of fibers: Carbon fibers have different tensile modulus grades (such as standard modulus, medium modulus, high modulus), as well as different filament specifications (such as 12K, 24K, etc.). For general reinforcement or conductive applications, the regular models can usually meet the requirements. When used in composite materials with high rigidity requirements, medium modulus products can be considered. Please inform us of your matrix material and performance goals before purchasing. 

Confirm the cutting length: The length of chopped carbon fiber is usually between 3 and 24 mm. For injection molding processes, it is generally recommended to use 6-12 mm, which is convenient for uniform mixing with plastic particles and less prone to damage; for compression molding processes or scenarios where longer fibers are needed to provide structural support, a specification of 12 mm or above can be selected. For powder coatings or fine filling scenarios, shorter specifications or carbon fiber powder should be used. 

Specify the type of sizing agent: The sizing agent is a coating applied to the surface of carbon fibers, used to protect the fibers and enhance the bonding strength with the matrix resin. Different resin systems (such as nylon, polypropylene, epoxy, polycarbonate, etc.) require different sizing agents for carbon fibers. When purchasing, please inform us of your matrix material so that we can select the appropriate sizing agent. 

Step 2: Evaluate quality and key acceptance criteria 

The dispersion, length uniformity and stability of the chopped carbon fibers, as well as the content of the adhesive (the amount of sizing agent), directly affect the performance of the composite materials. 

Focus on dispersion: When used in injection molding or extrusion processes, carbon fibers need to be uniformly dispersed in the matrix to avoid fiber agglomeration, which could result in uneven product strength or rough surfaces. Before purchasing, it is recommended to request samples and conduct a small-scale test according to your processing method (such as twin-screw extrusion) to observe the breakage situation and the degree of mixture uniformity. 

Testing length distribution: Request samples. Observe under a magnifying glass whether the fiber lengths are within the promised range, and check if there is a disproportionately high proportion of fibers that are too long or too short. Uniform length distribution is conducive to achieving more consistent material properties. 

Confirm the content of glue and ash: The content of the sizing agent (glue content) can affect the bonding strength between the fibers and the resin. The supplier is required to provide the test reports for the glue content or ash content of recent batches, and pay attention to the fluctuation range between different batches. 

Review batch retention samples: Determine whether the supplier retains samples for each batch and whether there are traceable records. This is helpful for conducting a review in case of quality disputes. 

Summary and Selection Suggestions 

When purchasing chopped carbon fibers, it is recommended to communicate in the following order: 

Define the substrate and process: What type of resin? Injection molding, extrusion, compression molding or other processes? This determines the length of the chopped fibers and the type of sizing agent. 

Confirm the strength grade and specifications: Inform the target modulus grade, length range, and filament specification. 

Sample machine testing: Conduct a small-scale trial on your production line to verify the dispersion effect, the uniformity of mixing, and the improvement in the performance of the final product. 

Yancheng Xiangsheng Carbon Fiber Technology Co., Ltd. specializes in the production and research of Short-cut carbon fibers and carbon fiber powders. We can match the sizing agent type according to your matrix material. Please feel free to request samples for testing and communicate technical requirements.