Technical evaluation : Methods for sealing paper/foil aseptic food packages

The process of sealing paper/foil aseptic food packages is similar to fusion bonding of two thermoplastic polymer layers, and it can be divided into four steps : heating of the surface, application of pressure, intermolecular diffusion, and cooling. The sealing techniques differ primarily in the heating method that is used. A variety of sealing methods were evaluated. Among the methods, two existing techniques (ultrasonic and induction sealing) and one new technique (infrared sealing) were regarded as the most promising. The effects of the sealing parameters on the process time and seal quality were studied. Ultrasonic sealing provides a short process time and consistent seal quality, with peel strength being limited by failure in the cardboard. However, breakage of the aluminum foil along the joint interface always occurs during ultrasonic sealing. Induction sealing also provides a short process time with consistent quality and no breakage in the foil. Infrared sealing was able to produce the same-quality seal as the induction and ultrasonic sealing. However, because that a longer process time is needed for stepwise operation, infrared sealing is more suitable for continuous sealing, such as the side seam of the packages. Application : ultrasonic, induction, and infrared sealing were found to be the most promising techniques for sealing paper/foil aseptic food packages.