High-intensity ultrasonication modification of vapor grown carbon fibers with poly(vinyl alcohol) for the preparation of high strength composites by simple water casting

High-intensity ultrasonication was demonstrated to be facile and efficient for the preparation of water-dispersible poly(vinyl alcohol) functionalized vapor-grown carbon fibres (f-VGCFs). In contrast to multiwalled carbon nanotubes, VGCFs are mechanically strong and not observably shortened or damaged by ultrasonication. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy show that the surface of f-VGCFs is decorated with a thin layer of PVA, imparting good dispersibility and suspending stability in water. High-strength PVA-f-VGCF composite films were then successfully obtained by the green and low-cost water casting method, which is totally free of organic solvents. The tensile strength and Young's modulus of the composite films filled with 5 wt% f-VGCFs are remarkably increased to 177.5 +/- 9.8 MPa and 4.6 +/- 0.4 GPa, respectively, which are about 45.0% and 53.3% higher than those of neat PVA. After being stretched by 5 times their length, the tensile strength and Young's modulus are increased to 681.0 +/- 4.3 MPa and 12.1 +/- 0.6 GPa, which are 58.8% and 49.4% higher than those of neat PVA stretched by 5 times their length, respectively. The uniform dispersion of f-VGCFs and the effective load transfer between the fillers and the matrix are responsible for the greatly improved mechanical properties.