Currently, the product certificates of most carbon fiber manufacturers include the following main contents: tensile strength, tensile modulus , elongation at break (performance indicators after the fiber is impregnated with resin); bulk density ; linear density; and sizing agent content .
Carbon fiber has a certain shelf life, which starts from the date of manufacture and is valid for two years , and the premise of this two-year validity period is that it is stored under normal temperature and humidity conditions . Since carbon fiber is a brittle material, it needs to be stored with extreme care. Take Torayca® carbon fiber from Japan's Toray Corporation as an example . In order to ensure that it will not be damaged during handling and processing, each roll of carbon fiber needs to be wrapped in plastic film, and the rolled carbon fiber products are protected by cardboard boxes and internal packaging to prevent vibration and shock. By wrapping in plastic film, the carbon fiber can also be protected from dust, moisture and other contamination .
Why is the shelf life of carbon fiber only two years? From the basic properties of carbon fiber, carbon fiber will not deteriorate over time due to its stable chemical structure. However, the carbon fiber surface sizing agent is a polymer that is affected by temperature, humidity and time , so no carbon fiber manufacturer can extend the warranty period beyond two years . Generally, carbon fiber products can be used stably and reliably within the two-year validity period.
Carbon fiber is a high-tech material that needs to be handled with care. As mentioned above, each roll of carbon fiber is individually wrapped in a protective plastic film, which must be carefully removed by hand when using it, and avoid using sharp objects.
Before using the carbon fiber, it is recommended to pre-treat the product. After removing the plastic film, each roll of carbon fiber must be stored for at least 48 hours at a temperature of 20-35°C and a relative humidity of 40-80% . Because this pre-treatment step is particularly important for the correct unfolding of the carbon fiber .
The right humidity will prevent the carbon fiber from rubbing against the reel , which in turn prevents the fiber from generating static electricity due to friction. Once static electricity is generated, it is easy to cause broken monofilaments to concentrate on the surface, which in addition to the loss of final product quality, may sometimes cause the carbon fiber to break.
Due to different carbon fiber processing techniques, the carbon fiber may be unwound from the reel in the axial or radial direction, but manufacturers generally recommend that customers adjust their process to radial wire feeding, which will reduce the friction of the fiber on the winding surface and the cardboard core shaft. In addition, the carbon fiber tension needs to be controlled.
