Surface Modification Of Carbon Fiber And Properties Of Its Polyurethane Matrix Composites

Carbon fibers can be used in military industry,public infrastructure,medical and industrial equipment,sports and leisure products,and fashionable life appliances.As reinforcing materials,carbon fibers are usually added to matrix to improve the overall properties of composites.Improving the mechanical properties of rigid polyurethane(RPU)materials by using carbon fibers as reinforcing materials has become a hot research field.Due to the inertness of the surface,it is necessary to modify the surface of the carbon fibers to improve the interface adhesion with the matrix or increase the physical interlocking with the matrix to achieve a certain performance of the composites.Firstly,the surface of the carbon fiber was treated by a simple and easy-to-operate high-temperature air oxidation modification,the interface layer of the carbon fiber surface was weakened,the surface roughness and the specific surface area were improved,and the active oxygen-containing functional group hydroxyl group could be introduced.Secondly,the electrodeposited nickel metal was formed on the basis of oxidation modification.The carbon fiber of dendritic metallization was prepared under the condition of voltage of 10.5V and 6 min.The results of electrochemical workstation showed that the nucleation was instantaneous in the early stage of nucleation.The rigid polyurethane-based composites were prepared by using pristine short carbon fibers,oxidized short carbon fibers and dendritic short carbon fibers,respectively.The effects of different modification methods and fiber mass fractions on the properties of short carbon fibers/rigid polyurethane composites were investigated.The results showed that the hydroxyl groups on the surface of oxidized short carbon fibers reacted with polyurethane to form covalent bonds,and the mechanical properties of the composites were improved to a certain extent,while the dendritic short carbon fibers could penetrate into the rigid polyurethane matrix,forming pinning effect,and producing synergistic effect,which greatly improved the mechanical properties of the composites compared with the pristine short carbon fibers composites.The tensile section of the composites showed that the interface bonding between the oxidized short carbon fibers and the matrix was better,and the dendritic short carbon fibers could effectively hinder the crack propagation and force the crack propagation path to change.In order to further enhance the reinforcing effect of carbon fibers on polyurethane materials,long carbon fibers were modified by air oxidation.The effects of carbon fibers length and content of long carbon fibers on the properties of rigid polyurethane composites were studied.The results showed that the mechanical properties of long carbon fibers composites were improved more than those of short carbon fiber composites,and the addition of long carbon fibers were beneficial to reduce the stress concentration point in the composites.