Hygromechanical Behavior of Cellulose-Based Materials

Cellulose is the most abundant biopolymer on Earth and, as most biological materials, has a hierarchical, anisotropic structure. Its mechanical properties are strongly influenced by environmental conditions such as temperature and moisture content. Especially the influence of humidity is very difficult to investigate. In most cases, water behaves like a plasticizer and leads to lower mechanical properties, swelling of the material and shows an apparent effect on the viscoelastic behavior of the material. This has strong implications for the technical use of cellulose-based materials. The production of paper is a classic example with the material going through different process steps, which have an influence on the chemical and physical properties, and at the same time also cause different hydration states in the material. When the product is finished and put into use, the effects of moisture changes trigger undesirable effects and have an impact on service life.<br/>Here, Brillouin Light Scattering Spectroscopy (BLS) is applied as a non-contact, optical method based on inelastic scattering of laser light by acoustic phonons in the sample material to study the mechanical properties. By using BLS, the mechanical behavior in the GHz frequency regime is investigated with a high time resolution during wetting and drying of cellulose-based materials. In this talk, first results of such experiments will be presented.