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 divi ded into four steps: heating of the surface, application of pressure, intermolecular diffusion, and cooling. The sealing techniques differ p rimarily in the heating method that is used. A variety of sealing meth ods were evaluated. Among the methods, two existing techniques (ultras onic and induction sealing) and one new technique (infrared sealing) w ere regarded as the most promising. The effects of the sealing paramet ers on the process time and seal quality were studied. Ultrasonic seal ing provides a short process time and consistent seal quality, with pe el strength being limited by failure in the cardboard. However, breaka ge of the aluminum foil along the joint interface always occurs during ultrasonic sealing. Induction sealing also provides a short process t ime with consistent quality and no breakage in the foil. Infrared seal ing was able to produce the same-quality seal as the induction and ult rasonic sealing. However, because that a longer process time is needed for stepwise operation, infrared sealing is more suitable for continu ous sealing, such as the side seam of the packages.