Evaluation of Frictional Influence and Thermal Analysis of Flexible Paper-Based Materials Used in the Vertical Form–Fill–Seal Process: An Experimental Study

Abstract

This study evaluated the frictional behaviour of flexible polymer-coated and dispersion-coated materials used in vertical form–fill–seal (VFFS) machines. A laboratory-scale friction measurement device was developed to investigate the relationship between different surface topographies, roughness and frictional properties. Furthermore, surface roughness, contact angle and surface energy of the material were analysed and a microscopic analysis was performed to further understand the effect of material properties on friction. Thermal camera analysis was performed to measure the temperature changes within the material during the film-transport stage of the VFFS machine. The friction measurement results indicated that the sliding direction did not affect the static and kinetic coefficients of friction. The significant influence of friction on the surface topography of the plate (forming shoulder and tube) was particularly evident. Some materials experienced the stick–slip phenomenon during sliding, depending on the surface type. Teflon tape, which is commonly used in the forming tubes of VFFS machines, exhibited the lowest coefficient of friction. Thermal camera analysis revealed that polymer-coated paper materials generated more heat than dispersion-coated papers during VFFS trials and thermoplastic films generated the least heat. No clear relationship between the surface roughness of the paper, fibre orientation, surface energy and friction coefficient was noted. Furthermore, paper-based materials exhibited a higher coefficient of friction, which is possibly related to the dispersion components of surface energy. The findings of this study provide additional knowledge for designing the forming tube, shoulder geometry and surface plate to minimize the occurrence of defects, such as wrinkles, in paper-based packages.