Properties of Polymer Composites Reinforced by Self-welded Carbon Fiber Networks

A new approach to self-weld the short carbon fiber (CF) into network throughout the matrix was proposed in this study. It was found that, CF owns strong interactions with nylon 6 (PA6), and adding small amount of PA6 leads to the formation of CF-PA6 networks in the PS matrix, as shown in SEM images and reflected by the platform of storage modulus at higher temperatures. Increasing the contents of PA6 improves the storage modulus at high temperatures, and enhances the strength of the self-welded networks. As a result, the ternary composites behave a remarkable increase in the heat distortion temperature. As carbon fiber possesses superior thermal and electrical conductivity, the composites show a lower electrical percolation threshold and a higher in-plane thermal conductivity. Further analysis demonstrated that the encapsulation of PA6 on the CF surface is a kinetic process, and the storage modulus at 180 degrees C increases linearly with encapsulation ratio of PA6, N-PA6. Experimental results confirm that a larger difference in viscosities between PA6 and the matrix is benefit for increasing N-PA6, while a longer hot-press time promotes preferential segregation of PA6 on the CF surface and further toward the intersections of CF, and thus greatly improves the mechanical strength of the networks.