Advanced fiber characteristics by carbon nanotubes – What we did not expect

 Andres Petr1, Steffen Oswald1, Robert Heider1, Johanne Neuhof2, Silke Hampel1
1 Leibniz Institute for Solid State and Materials Research Dresden;
2 Faserinstitute Bremen e.V.

Carbon fiber (CF) reinforced plastics were widely used as construction elements where weight saving is an important issue. We tried to further increase the stability of such elements by generation of a hierarchical structure of CF and carbon nanotubes (CNT). The direct growth of CNT on CF should increase the mechanical stability of the fiber polymer composite. This will also occur if not all CNT are very strongly bound to the CF due to a CNT dispersion in the matrix without CF will also increase the mechanical stability of the composite but much less effective. More important than the strong bonding of the CNT are the presence of suitable surface groups on the CF and the CNT for a strong interaction with the used polymer. We learned that the concentration of such groups is strongly reduced during the growth of CNT. Therefore an additional oxidation step after the growth of CNT to produce new surface groups is very important.

As a catalyst for the CNT growth we used electrochemically deposited Co-nanoparticles which were oxidized in air to avoid the reaction of metallic cobalt with the CF at the temperature of the CNT growth.

Even with CF grafted with CNTs without the final oxidation step we got an improved pull out value of the fiber. An appropriate surface modification of the CF equipped with CNT will further increase the interaction of the fiber with the polymer matrix and improve the mechanical properties.