Influência da higroscopia na estabilidade dimensional do papel cartão

Abstract

The paper is manufactured with cellulose fibers, which are deposited on a fabric, having a preferential orientation. Board paper is typically formed by multiple layers, making this orientation even more complex. Different orientations can generate residual stresses, causing the material to lose its flatness. Making everything more complicated, cellulose fibers are hygroscopic, and their final equilibrium moisture content depends on the composition of each fiber type in question. As they absorb or lose moisture, the size of the fibers is modified, and therefore the resulting residual stresses change. The aim of this study is to analyze the effects of moisture on the different layers of paper and its effect on the flatness of the paper. To achieve this, a dimensional study was conducted after delamination of the layers, enabling the evaluation of each layer at different equilibrium moisture contents. A significantly different hygroscopic behavior was found between the top layer and the base layer, with the top layer being less hydrophilic than the base layer. There is also greater dimensional stability in coated paper compared to uncoated paper, which contributes to the dimensional stability of the final product.