IMPROVEMENT OF MECHANICAL-PROPERTIES OF COMPOSITES THROUGH POLYAMIDE GRAFTING ONTO KEVLAR FIBERS

Chemical modifications of the surface of Kevlar fiber were investigate d as a means of improving fiber-matrix adhesion. The fiber surface was used as a polymerization support for interfacial polycondensation. Ny lon-6,6 was successfully polymerized in this way. The grafted nylon wa s characterized by ESCA (electron spectroscopy for chemical analysis), DSC (differential scanning calorimetry), and extraction procedures. A n increase of the transcrystalline layer thickness was observed throug h optical microscopy, indicating better fiber-matrix adhesion. Both pl asma treated fibers having been submitted or not to chemical treatment s were used as reinforcements for nylon-6,6 unidirectional composites. Improvement of the mechanical properties were related to better inter facial interactions due to grafted nylon chains.