Influence of moisture content on sealability and convertibility of coated papers in vertical form fill seal (VFFS) machines

Abstract

The effect of moisture on the sealability and converting efficiency of fiber-based packaging materials depends largely on coating type. Dispersion-coated papers exhibited inconsistent behavior with an increase in moisture content, while polyethylene-coated papers' seal strength is relatively higher and possesses stable values. This study focused on analyzing the influence of different relative humidity levels and temperature conditions on sealability and convertibility of polyethylene and dispersion-coated papers on vertical form fill seal (VFFS) packing processes. The experiments were carried out under three climatic conditions: 50% RH at 23 °C (standard), 80% RH at 23 °C (high humidity), and 85% RH at 38 °C (tropical). To determine the performance of materials, seal strength, sealing window properties, frictional resistance, and surface roughness were measured. The dispersion-coated papers showed a slight increase in seal strength under tropical conditions. However, they possess a narrow sealing window and inconsistent behavior as humidity and temperature increased, but PE-coated papers demonstrated uniform behavior. Static and dynamic coefficients of friction and surface roughness values indicated that dispersion coatings softened with the rise in moisture, which can lead to enhanced feeding resistance and runnability. The findings demonstrate the importance of humidity and temperature control in the achievement of reliable performance of the packaging. The results are useful in terms of optimizing the process parameters and contributing to the transition over to sustainable fiber-based packaging materials.