Viscoelasticity and Solution Viscosity of Perfluoropolyether Disk Lubricants

초록

Viscoelastic properties which include the storage modulus, loss modulus, loss tangent, and creep recovery, of perfluoropolyether (PFPE) lubricants with polar end-groups were examined using a rotational rheometer with a double gap geometry. Both temperature and molecular weight dependences were measured and analyzed via polymer relaxation process models. The modified Cole-Cole plots for storage modulus vs. loss modulus exhibit the presence of microstructures originating from the interaction among PFPE end-groups. Further, we correlated our viscoelastic data with various other experimental results, including the tribological data. Beyond the melt rheological studies, we examined the solution viscosity as well. To determine the solvent effect on the roughness and uniformity of PFPE thin lubricant films during the dip-coating process, we examined the viscosity for dilute PFPE solutions, which depend on the aspect ratio of PFPE molecular clusters and the potential energy among PFPE molecules. We found that the intrinsic viscosity and/or the Huggins coefficient, measured at an early stage of the manufacturing steps, were related to the film morphology, or media noise.