Innovative focused ultrasound‐based sealing method of flexible packaging films—Principles and characteristics

Abstract

A key process to package goods is the closure procedure. It ensures the good protection against the environment and vice versa. Ultrasonic sealing presents the advantage of converting locally ultrasound into heat, which is optimal for temperature sensitive goods. The disadvantages remain, however, the equipment cost, the noise generation, and the process sensitivity to materials. It is necessary to develop a sealing process to decrease the acquisition cost of the sealing equipment and cover a wide range of polymer films.This paper focuses on a new sealing method based on high‐intensity focused ultrasound. The principles and characteristics of this process are discussed and underpinned with experimental results.Both the acoustic and thermal effects of the sealing process are summarized. A study of the process parameter impact on the seam strength in static and dynamic operating is proposed. Low‐density polyethylene films with a carrier layer of bi‐oriented polypropylene and polyethylene terephthalate are used. A first test bench generates point‐shaped seam. The heat generation is recorded with an infrared thermography system. A second test bench, a horizontal form fill and seal machine, produces longitudinal seams. The seam quality is controlled by tensile test and tightness test.A quick heating of the polymer films is found. Point seams and longitudinal seams are successfully generated. The seams behave similarly to the ones generated with ultrasonic sealing process. However, the sealing velocity is limited to 3 m/min.This work provides a summary of the characteristics and principles of the new sealing method in packaging applications.