The processability of polyethylene coextruded films and laminates in vertical form film seal (VFFS) packaging machines is analyzed vis-à-vis the melting behavior and rheology of sealant polymers, using a simple analytical approach accounting for heat transfer, squeezing flow, and geometry of seals. The processing window for pillow pouches with a vertical fin seal is characterized by cycle time-temperature combinations that give hermetically sealed pouches, and formation of defect-free integral seals, at high speed steady-state operation. The processability window is shown to be governed by rate of heat transfer, strength evolution at the sealant interface as controlled by polymer melting profiles and rheology, and flow of the semi-molten sealant into gaps and discontinuities. The influence of contaminants on hermeticity window is illustrated with data and models, as are effects of material selection and blending. Recent results on finite element simulations of drop tests of VFFS pouches are also illustrated, highlighting the influence of material selection and pouch geometry on drop impact resistance.