AbstractsEngineering

The feasibility of sealing three-layer aluminum foil-based flexible laminates using ultrasound technology was studied. The experimental results of seal evaluation provide sufficient evidence that ultrasonic sealing of MRE (Meals Ready to Eat) foil laminate package is technically feasible.High peeling strength seals were produced with different types of techniques and welding equipment. Both continuous and stationary ultrasonic sealers were involved in creating strong seals combined with knurled or smooth surface anvils. Two ultrasonic frequencies were investigated, with 40-kHz in addition to the industry standard frequency 20-kHz to broaden the scope of research. Although seals meeting set criteria for thepeeling strength were produced in both cases, the 20-kHz stationary sealer provided seals with the highest peeling strength.The process selection is critical to minimize material damage in the seal zone by ultrasonic tool vibration. It was shown that aluminum was particularly sensitive to the sealing technique and anvil type because it was easily damaged. Successful seals with no material damage and high peeling strength (average value 17.4 lbs./inch) were produced on a 20-kHz stationary sealer with a fine female-knurled anvil.Ultrasonic sealing is remarkably tolerant to seal contamination. As tested with two contaminants, sweetened water and muffin crumbs, the seals still exceed specification. Ultrasonic tool vibrations could diminish the contaminants' interference with seal formation, and high-quality seals were produced. Seals contaminated with crumbs (more than 20% of the seal zone was contaminated) still had a peeling strength twice the criteria and the uniformity of seals was not compromised.It is proved that ultrasonic sealing is a promising technique for foil-based flexible food packages. Stationary sealers have been confirmed to meet specifications, while continuous welding must be further optimized to reduce damage to the foil layer.