Production of advanced 3D-shapes for packaging from paper-based materials

Paper-based materials are widely used in various types of packaging. Paper and paperboard are printable, recyclable, biodegradable, renewable and sustainable materials having certain advantages over most of the plastic-based packaging materials. However, they are lacking certain barrier properties and flexibility in terms of package design; i.e. paper packaging appears in rather simple geometrical forms while plastics can be formed to the multiple shapes. Overcoming the insufficient formability of paper is the key to novel packaging applications, and eventually to the strengthening of the role of paper on the world packaging market. 3D forming processes such as deep-drawing, vacuum-forming, thermororming etc. are used for the production of advanced 3D shapes from paper. One of the primary requirements of paper in these processes is the extensibility. However, paper materials which are currently available on the market have relatively low extensibility values which limits outcome of the forming process to simple shapes. This presentation aims to review a recent progress in the development of novel, formable paper with high extensibility, and in the research of various 3D-forming processes. A combined approach was utilized to improve extensibility of paper, it includes: mechanical modification of fibres using combination of high- and low-consistency mechanical treatment, improvement of fibre bonding by adding various carbohydrates, modification of fibre network by compaction, and unrestrained drying. As a result, papers with extensibility ranging from 15%-points to 30%-points were produced. Additionally, it was possible to improve barrier properties of apper, wet web strength, and decrease water vapor permeability. Improvements in extensibility of paper obtained with utilization of combined approach were further assessed for their practical relevance in the production of advanced 3D-shapes, using four pilot and laboratory scale forming devices. However, some of the above mentioned treatments improving the extensibility of paper have a negative effect on the surface smoothness and propose a challenge for the printability of the material. The forming experiments showed that the forming conditions such as moisture content of paper and temperature in forming have a significant impact on the results of forming. Elevated temperature and moisture content can improve the formability of the paper by 30-50%. Produced paper with high extensibility showed superior performance to currently available commercial papers.