Influence of Moisture, Temperature and Bleaching on the Mechanical Properties of Coated Fiber-Based Substrates

Abstract

Substrates from fibrous materials are widely used in packaging applications and are produced in high quantities on roll-to-roll production lines. The anisotropic material behavior presents a demanding situation for the process control of the converting step. In this work, the influence of moisture and temperature on the mechanical properties of coated and uncoated fiber-based substrates and the influence of other material properties were investigated. The change of moisture content in relation to the surrounding temperature and relative humidity was investigated for different products. The hygroexpansion in dependence of the humidity is measured in machine and cross direction. The changes in the mechanical properties of the different materials due to changes in moisture content were investigated by tensile testing. The material behavior was highly responsive to the surrounding humidity and, thus, the material’s moisture content. A relative humidity between 60% and 70% showed the influence on the material properties most clearly. The presented work showed an influence of the coating on the moisture content for higher grammages. The effect of bleaching was also investigated. Bleaching decreases the potential for moisture absorption and, therefore, influences the moisture content and properties such as hygroexpansion. Coatings influence the hygroexpansion in an anisotropic manner. Coating and bleaching also influence the tensile properties of fiber-based materials. This article is an expanded version of a talk given at the 14th European Coating Symposium, 6–9 September 2021, Brussels, Belgium.