Beschreibung:
Fluorocarbon films can provide barrier properties such as hydrophobicity and oleophobicity to paper- and cellulose-based materials. While qualitative methods such as “oil kit tests” provide information on grease barrier properties, they do not quantify the extent of grease barrier properties. In this study, we report the sorption and desorption behaviors of a grease surrogate (hexadecane) vapor in plasma polymerized fluorocarbon films deposited from pentafluoroethane. Three different film thicknesses (0.5, 0.75, and 1μm) were exposed to varying concentrations of hexadecane vapor and uptake evaluated using a quartz crystal microbalance. The amount of hexadecane sorbed in the fluorocarbon film increased with hexadecane concentration until film saturation occurred, at which point the mass of hexadecane sorbed no longer increased with concentration. While the amount of hexadecane sorbed for a given hexadecane concentration increased with film thickness, the wt % of hexadecane sorbed into the fluorocarbon film was essentially independent of the film thickness reaching ∼0.6% of the maximum hexadecane concentration studied for all film thicknesses. These results indicate that fluorocarbon films have low affinity for hexadecane vapor. Transient sorption and desorption studies were also conducted using hexadecane vapor; both processes followed dual-mode sorption behavior. Diffusivities of hexadecane as determined from sorption and desorption were ∼10−13cm2∕s.