Perfluropolyether (PFPE) thin films perform critical lubrication and wear-resistance functions in magnetic data storage systems. To provide strong anchoring, PFPE oligomers with terminal hydroxyl groups are bonded to the underlying media by a heat treatment that gives rise to hydrogen bonding between the PFPE endgroups and polar groups on the media. The disjoining pressure of PFPE films is an important operational parameter used to judge their flow properties in the presence of externally imposed defects, and can be assessed using AFM-derived force-extension curves. Here, the AFM probe is initially contacted to the PFPE film, then retracted at a slow rate, stretching the liquid bridge formed between the probe tip and the film substrate. Various models, including one developed in our previous work, can be used to fit these force-extension curves to obtain the disjoining pressure. This methodology fails in the case of bonded PFPE films, as the flow dynamics are too slow to establish equilibrium between the liquid bridge and the underlying film during the stretching experiment. We have made the interesting (and to our knowledge, unique) observation that AFM force curves collected on the approach cycle show an apparent film expansion as the tip-surface force is increased. Further, this unusual feature becomes more pronounced as the extent of PFPE bonding is increased, and is non-existent in the absence of bonding. We believe the feature is likely due to the flow of PFPE material displaced by the initial contact back into the film surrounding the AFM tip, providing a transient repulsive force. The size of the feature also decreases as the approach rate is slowed. We will discuss attempts to model this process to provide physical insight and measures of PFPE performance in data storage systems.