Materials Taking
Materials Taking sustainability one big step Home-compostable coffee capsules made of renewable resources Biopolymers and ecofriendly solutions for packaging materials are becoming more and more relevant as it is important to reduce aluminium and fossilbased waste and the need for materials increases that both protect and enhance shelf life of food and reduce packaging waste. In 2018 (cf. bM 04/2018) Samantha Onderka (19) and Katharina Schleinzer (18), two students from the TGM, Vienna’s biggest engineering college, developed a material that could be processed into coffee capsules and was completely home compostable (Fig. 1). Due to its importance, two more students from the TGM, Anna-Maria Monks (19) and Judith Nachbagauer (18) continued the project in 2019 in cooperation with Gabriel-Chemie, a family-owned business and one of Europe’s leading masterbatch producers, with its headquarter in Gumpoldskirchen, Austria. The main focus of the diploma thesis was the optimization of the material for compostable coffee capsules so that its properties equalled or came close to those of the popular aluminium capsules. The aim was to create an alternative, based on renewable resources, to replace these as they have a massive negative impact on the environment. In order to optimize the compound, the two graduates developed several additional materials of differing compositions that would in theory optimize the compounds to test and compare their mechanical properties, such as tensile properties or thermal properties, e.g. the Vicat Softening and Heat Deflection Temperature (Fig. 2). Therefore, the developed compounds were injection moulded to test specimens and characterised extensively. Fig. 1: Home-composting process of coffee capsules made of a self-developed biopolymer compound “We spent many hours developing a list with possible components and their compositions and many days to produce each compound, and were really relieved when, in the end, one compound showed optimal properties” says Anna-Maria Monks, who was responsible for selecting and developing the compounds. Not only were the mechanical and thermal properties critical. The product had to comply with criteria according to the (European) “Commission Regulation (EU) No 10/2011 on plastic materials and articles intended to come into contact with food”. “It is proven, that the developed biopolymers could have a very strong migration behaviour. Therefore, it was important to us, that the migration behaviour of each chosen compound was tested as it wouldn’t be ideal if the coffee tasted of a biopolymer”, says Judith, whose task was to test and ensure the product specific properties as a coffee capsule adhered to the Regulation. Coffee capsule production, however, requires the material to be processed via injection moulding or as a flat film. Hence, the two students processed the chosen compounds also into extruded films. The students then put their focus on developing a method to measure the migration behaviour of several compounds. This test consisted of forcing hot water through the film in order to determine if the biopolymer migrated into the water that streamed through the film (Fig. 3). To visualize any migration, a chemical was added to the compound that would Determination of Vicat softening temperature according to ÖNORM EN ISO 306:2014 (Test load: 10 N, heating rate: 120 °C/h) 120 Vicat softening temperature [°C] 105 90 75 60 45 30 15 limit 0 INN90/11 INN90/12 INN90/13 INN90/14 INN90/18 INN90/20 Fig. 2: Vicat Softening Temperatures of several tested compounds 40 bioplastics MAGAZINE [02/20] Vol. 15
Materials further By: Christopher Fischer TGM - Die Schule der Technik Vienna, Austria discolour the water, if traces of the biopolymer had migrated. When discoloration was experienced, a sample of the discoloured water was taken and further tested. The migration behaviour was not the only specific property that needed to be tested. The students explain that in the so-called broth-part of the machine, the coffee capsule is inserted and pierced by three needles. Therefore, it was equally important to determine the piercing behaviour of the compounds. Using a 3D-CAD program; a test setup was designed and 3D-printed. By using a universal tensile testing machine, the coffee capsule was pushed down on the needles, simulating the process in a coffee machine (Fig. 4). Fig. 3: Self-developed setup for the simulation of the hot water migration If the material was too thick or too tough it could have led to the capsule being squeezed rather than pierced or the needles may even be damaged. To establish the quality of the test scenario, aluminium capsules were used initially which showed that the test worked well and was qualified to simulate the piercing behaviour of the self-developed biopolymer compounds. After spending six months on the diploma thesis, Anna-Maria and Judith, together with Gabriel-Chemie are happy to report, that they have developed a compound that not only fulfils the mechanical, thermal and specific product requirements for coffee capsules but a material that can also easily be used in their production using a thermoforming machine. The two students added: ‘The properties of the newly developed compound equalled those of the aluminium capsules and therefore can be used as a substitute for aluminium coffee capsules to lighten the aluminium load of our planet.’ Nevertheless, some open tasks remain, such as the optimization of the geometry or the approval for food contact. Due to the proven home-compostability properties, the usability of the developed material for compostable food packaging is promising. Fig. 4: Self-developed setup for the characterisation of the piercing behaviour of coffee capsules While the work of Anna-Maria and Judith shows the great potential of sustainable products, their work had already drawn the attention of several prominent institutions and companies, which honoured the effort of both graduates with multiple awards. Up to now the two young plastic engineers were awarded with the Borealis Innovation Award 2019 (Borealis), the Polymer Science School Award 2019 (University and Polymer Competence Center Leoben), the Qualify.ing Contest Award (Alumni Club of the TGM) and with the wienING Award 2019 (Vienna Federal Economic Chamber). www.tgm.ac.at | www.gabriel-chemie.com bioplastics MAGAZINE [02/20] Vol. 15 41
