The impact of interface characteristics on the recyclability and repulpability of packaging material

Sammanfattning: The world is slowly moving towards a more environmentally friendly mindset and many companies, such as Tetra Pak® have followed this lead by producing more environmentally friendly products and developing better materials with less environmental impact. To accommodate these requirements, it is important that the package is recyclable. For a carton this is defined by the repulpability, i.e., the ability of the material to disintegrate and the fibers to disperse. Cartons consist of several layers containing different materials, such as plastics, cellulose and a barrier (that usually consists of aluminum foil). Together they give the package all of the wanted properties. The parts of the material that consists of fibers need to be separated from the polymers and aluminum during the repulping in order to be able to be repulped and thereafter further recycled. This thesis examines the method and repulpability and investigates the influence of interface characteristics on the recyclability of three materials, packaging material A, B and C (C has an aluminum barrier and A and B have fiber-based barriers). Different parameter settings, such as temperature, rotor speed, pre-soaking, moisture content and pH have also been investigated during the repulping process using the three forementioned materials. The pulp was analyzed visually by making paper sheets out of the pulp, and quantitatively by doing further test on the pulp after the repulping to determine its quality. It was found that different parameters influenced the repulping time as well as the fiber flake content. The drainability was mostly influenced by the different properties of the materials, and the fibers in reject and flake content were influenced by both material properties and parameter settings. Based on the results, a higher temperature than 43°C should be used when running the repulping trials, as it decreases the repulping time, and with it, energy consumption of the pulper. Material C gave the best recyclability out of the tested samples, and material A was the best alternative regarding the recyclability out of the two materials with fiber-based barriers. Material A would therefore be interesting to use for further research and development of recyclable material.