Electromagnetic waves have gradually become the fourth largest environmental pollution in addition to water, air, and noise. In addition, the electronic, electrical and communication equipment manufactured by people will also produce electromagnetic radiation, and the development and research of electromagnetic shielding materials has gradually become an issue of increasing concern. Carbon fiber has good electromagnetic shielding performance, and carbon fiber has excellent electrical and thermal conductivity, good flame retardant performance, very low thermal expansion coefficient, low radiation absorption and a series of advantages.
Electromagnetic shielding is the use of conductive or magnetic materials to limit electromagnetic radiation within a specified space. There are generally two purposes of electromagnetic shielding, to restrict internal radiated electromagnetic energy from leaking out of the internal area, or to prevent external radiation interference from entering a certain area. According to the shielding principle, electromagnetic shielding can be divided into three types: electric field shielding, magnetic field shielding and electromagnetic field shielding. The essence is to study how electromagnetic fields are distributed in various specific problems.
There are many ways to classify electromagnetic shielding materials, mainly including ferromagnetic materials and metal good conductor materials, surface conductive shielding materials and filled shielding composite materials. Among them, the filled shielding composite material is an electromagnetic shielding material product composed of a matrix with good electrical insulation, conductive fillers with excellent conductivity and other additives, and carbon fiber belongs to this electromagnetic shielding material. Under the harsh conditions of 60℃ and relative humidity of 90%, after 2000h durability test, the carbon fiber shielding material made of carbon fiber with a length of 3mm and CF/PVC resin with a content of 5wt% can achieve a shielding effect of more than 30dB. The CF content is 10wt%hi, which can achieve a shielding effect close to that of copper foil.
The main reason why carbon fiber has electromagnetic shielding ability is because of its good electrical conductivity. The common volume resistivity of carbon fiber is between (0.8~1.8)×10-3Ω·cm, and the conductivity will increase with the increase of heat treatment temperature. Therefore, after high-temperature graphitization treatment, carbon fiber can become an excellent reflective material for electromagnetic waves. At present, the research on carbon fiber by state-owned enterprises is mainly focused on the mechanical properties, and the research in the electromagnetic field is still relatively small.
Post time: Oct-18-2021