Shaft seals shall prevent the leakage of oil and the intrusion of dirt particles in rotating machineries. A loss of contact between shaft and seal results in leakage. In order to ensure the functionality of the sealing system, the followability of the seal needs to be ensured. To analyze this problem, a model of a Polytetrafluorethylen (PTFE) shaft seal is coupled with an unbalanced rotor. PTFE has pronounced viscous and plastic characteristics. This leads – combined with other non neglectable nonlinearities – to a numerically challenging problem. To reduce the complexity and to increase the computational efficiency, the PTFE shaft seal is discretized by a quasi-axisymmetric lattice model. The results show that loss of contact at rotor speeds close to the eigenfrequency of the rotor (high amplitude) and at high rotor speeds (high frequency) is possible and shall be avoided to prevent leakage.