Modeling and experimental analysis of squeeze flow of sealant during hot bar sealing and methods of preventing squeeze-out

Abstract

Excessive pressure and temperature during hot bar sealing of flexible packaging films can result in seal failure due to squeezing out of the sealant from the seal area. A model is developed that shows the amount of squeeze-out increases with increasing seal bar pressure, seal temperature (by lowering the viscosity of the sealant), sealing dwell time, film thickness, and decreasing seal bar width. Validation experiments qualitatively agree with the model predictions. Both the model and experimental results show that the rheology of the sealant plays a significant role in preventing squeeze-out; high viscosity at low shear rates favor less squeeze-out. The work shows that under normal sealing conditions, squeeze-out is not substantial. Avoiding excessive temperature or pressure is critical to minimizing squeeze out to ensure good sealing performance.