Regulation of Rheological Behavior of Polyvinyl Alcohol Aqueous Solution by One-dimensional Particles

In this paper, one-dimensional particles were added into polyvinyl alcohol(PVA) aqueous solution. The effects of oxygen-containing functional group content(hydroxyl value) on the surface of carbon particles, aspect ratio(L/D), temperature and PVA bulk solution concentration on the rheological behavior of the composite solution were investigated. The results show that carbon nanotubes(CNTs) and carbon nanofibers(CF) can regulate the rheological behavior of PVA aqueous solution by changing hydroxyl value and L/D. The viscosity(eta) of the composite solutions first increases, then decreases, and then continues to increase with the amount of CNTs(phi(CNTs)), showing an N shape change trend. There are two transition points, i.e. phi(1) and phi(2). CNTs mainly play a role of physical crosslinking point at phi(1), and the eta increases; while CNTs destroy the intermolecular hydrogen bond interaction of PVA chains most seriously at phi(2), leading to a lower eta than that of pure PVA solution. With the increase of hydroxyl value, the interactions between CNTs and PVA chains are strengthened, giving rise to the decrease of both phi(1) and phi(2). Furthermore, eta corresponding to phi(2) decreases. This indicates the viscosity reduction effect is strengthened by the high hydroxyl value of CNTs. With the addition of CNTs, the hydration number of the composite solution decreases, implying that more hydroxyl group of PVA chains form hydrogen bond interaction with CNTs. The CNTs composite solution with high hydroxyl value has lower hydration number than that with low hydroxyl value. The viscous activation energy of the composite solution increases with phi(CNTs). CNTs have similar regulatory effects on eta of PVA solutions with different concentrations, but the regulatory range is different. The viscosity regulation of PVA aqueous solution by CNTs with the same hydroxyl value and different L/D also show an N shape curve, but short CNTs composite solution with small L/D have large phi(1) and phi(2). While the composite solutions containing CF with similar L/D but larger diameter show lower phi(1) and phi(2).