Influence of process parameters on sealing strength of polymer films in an innovative continuous heat sealing technology

Abstract

An innovative process for packaging films sealing has been recently promoted: Heat is provided on the upper side of the polymer films. In this paper, sealing conditions are studied for two PET‐PE films. Melting temperature of the sealant layer material was determined by differential scanning calorimetry (DSC), through both conventional and successive self nucleation and annealing procedures. Interface temperature was measured during sealing, and a temperature model was fitted to compute the effective sealing time for each process parameter. Unconventional T‐peel tests were established with disk‐shaped seal samples. Strengths of the seals formed for different process parameters were measured. Results have shown that the melting temperature measured by DSC (108° C and 99° C for PE70 and PE120, respectively) is the seal initiation temperature of the materials. Results of T‐peel tests can be divided in two regions: A growth region where seal strength values increase, up to a threshold at which the seal strength is almost constant (20 N/10 mm). In the growth region, we propose a time–temperature relationship between seal strength, tool temperature, and effective sealing time in the form of an Arrhenius model CexpαTtn . The value of the time exponent n in the model is in agreement with what the chain diffusion theory predicted (n=0.5) .