Energy-efficient construction by composite materials with paper

Paper is a natural material obtained from renewable raw materials, which has been used for many centuries in the building industry (mainly in interior finishing). Paper can be produced cost-effectively in large quantities, is recyclable in many cases and offers a variety of possibilities for functionalisation in line with requirements thanks to the chemically reactive hydroxyl groups of cellulose. Compared to wood, paper can be tailored much better for specific applications. Despite these manifold possibilities, the possibility of using paper-based structures in combination with mineral materials in the construction industry has hardly been systematically investigated so far. There are a few examples of such composite materials, such as gypsum plasterboards or investigations on fibre-reinforced cement or concrete.

The aim of the project is to develop new, particularly energy-efficient concepts with composite materials based on paper, mineral building materials and plastics for functionalisation (e.g. for adhesion promoters or hydrophobisation). These concepts should be particularly suitable for constructing energy-efficient components, e.g. for building envelopes. Energy efficiency refers both to the thermal insulation properties during application in the building and during the production of the material itself and during the application of the materials.

On conventional paper machines it is possible to influence the fiber orientation, but only to a limited extent. For the production of highly unidirectionally oriented papers, a laboratory plant based on the work of Kortschot is currently being built and tested. This is being further developed in such a way that a higher fibre orientation and thus a considerably higher relative tensile stiffness in the longitudinal direction is possible. Thus, the potential of unidirectionally oriented papers can be demonstrated and a relationship between degree of orientation and strength values can be determined.

For construction applications with paper, only very few specifically designed and manufactured papers are used today. The potential of paper as a building material is therefore far from exhausted today.

For this purpose, work package 1 will characterize pulp, paper and paper products of selected industrial partners, test and extend strength models and optimize the fiber orientation in paper.

The relationship between the stress distortion behaviour of paper or fibre and the later composite material is currently unknown. Although validated models exist, there is no suitable input variable for these models to quantify the contribution of fiber reinforcement.

By comparing the results from the characterisation of existing nonwoven materials with existing models for the strength of paper and paper composites and, if necessary, adapting these models, the optimisation can be model-based and the findings can be more easily transferred to industrial scale.

At the beginning of the project, the materials available at the industrial partners will be characterized with regard to their strength characteristics and thermal conductivity. This data will later serve as a reference for the production of fiber nonwovens optimized for energy-efficient construction, the development of a technique for the production of highly unidirectional oriented papers and for modelling the relationships between process variables and mechanical paper properties.