Carbon Chopped Fiber is a product made by chopping carbon fiber tow.
Carbon Milled Fiber is a product made by grinding milling chopped fiber into a powder (milled) form.
Chopped fiber is typically around 3 to 6 mm long, while milled fiber is typically less than 200 µm long. Both of these materials are used to enhance the physical properties of thermoplastic resins and rubbers, and to increase electrical and thermal conductivity.

Carbon Fiber & Carbon Fiber Reinforced Plastics Special Site
『Carbon Chopped Fiber & Milled Fiber (Short fiber)』[Open in a new window]