Heat sealing and convertibility of coated paper materials in vertical form fill and seal machine

Abstract

Challenges regarding the heat sealing and convertibility of coated papers in vertical form, fill, and seal (VFFS) machines were investigated. This research focused on enhancing the use of coated papers in VFFS packaging machines by identifying the optimal sealing parameters to ensure package tightness, evaluating friction-related issues to improve runnability, and developing a novel forming shoulder design to optimise material formability and minimise oil and grease properties damage during the conversion process. To understand the performance of various coated papers in VFFS machine, PE-coated and dispersion-coated papers were tested and compared with conventional thermoplastic films. The seal properties and integrity were examined using seal strength and leak tightness measurements. Additionally, the frictional properties of the coated papers were investigated on different surfaces to identify the appropriate surface for paper runnability. The seal structure and surface characteristics of the converted packages were analysed using SEM and 3D profilometry. Finally, oil and grease measurements were performed to evaluate the impact of wrinkles on converted pouches. The results indicated that achieving an airtight seal with coated papers requires precise control of the sealing process parameters, with serrated seal bars significantly improving the seal integrity by creating localised shear stress that enhances polymer chain entanglement. Frictional analysis revealed that the coefficient of friction was a critical factor affecting the runnability of the material in VFFS machines. The Teflon-coated forming tube and pattern-rolled 5WL stainless-steel surfaces effectively reduced friction and improved material flow over the novel forming shoulder. The new shoulder design features an optimised bending curve and other geometrical parameters that successfully minimise wrinkles and tears on the coated paper packages after the conversion process. Through precise control of sealing parameters and advancements in tooling design, this study offers the ability to use sustainable materials in VFFS packaging. The proposed modifications to VFFS processes enhance the practicality of adopting environmentally friendly packaging solutions in the food industry and other fields.ei tietoa saavutettavuudest