Basics Sustainable
Basics Sustainable Plastic from CO 2 Waste Fig. 1: Vacuum cleaner cover By Robert Greiner Corporate Research and Technologies Siemens AG Erlangen, Germany Fig. 2: Door-holder for refrigerators As part of the project ‘CO 2 as a polymer building block’, funded by the German Federal Ministry of Education and Research, scientists from Siemens Corporate Technology, together with their project partners from BASF, the Technical University of Munich and the University of Hamburg, have been seeking an alternative for the standard plastics ABS (acrylonitrile butadiene styrene) and PS (polystyrene). Both plastics are frequently used in consumer products. Compounds based on PHB (polyhydroxybutyrate) could be a competitive alternative to ABS. PHB is a polymer produced by micro-organisms as a form of energy storage molecule based on sugar (mostly cornstarch) or plant oils as renewable feedstock. But PHB is a very brittle plastic and, unless modified, is unsuitable as a material for example for housings. A transparent alternative to PS could be compounds based on PLA. For these two materials polypropylene carbonate (PPC) can be used as an impact modifier. PPC is an amorphous thermoplastic material and shows a glass transition temperature of around 30 °C. Thus it is very flexible at room temperature, and moreover it shows at least a partial miscibility with both bioplastics and therefore it is suitable for adjusting the ductility of PHB and PLA. PPC consists of around 43% by wt. of carbon dioxide obtained by removing CO 2 from waste gases, e.g. from power plants. The copolymerization occurs with PO (propylene oxide) in the presence of appropriate catalysts. These catalysts are the key to a new CO 2 -chemistry which uses carbon dioxide as a valuable resource for base chemicals. H 3 C O CO 2 catalyst CH 3 O O C O n propylene oxide polypropylene carbonate 48 bioplastics MAGAZINE [05/12] Vol. 7
Basics Polypropylene carbonate is highly clear, biodegradable, stable under UV light and easy to process by injection moulding or extrusion. The following new formulations were developed as green alternatives to ABS and PS (figures in weight percent): A) ABS alternative: ((PHB (70 %) + PPC (30 %)) + talc (10 %) + carbon black master batch (3 %) B) PS alternative: (PLA (70 %) + PPC (30 %)) + green pigment (0,25 %) In table 1 some properties of the new compounds are given in comparison to ABS and PS. In comparison with the standard materials the green compounds show an absolutely satisfactory property profile. With the recipe A merely the impact strength falls off noticeably compared to the ABS. With the recipe B the heat distortion temperature is below that of the PS but toughness is increased significantly. In both green compounds there is a better ecological balance compared to ABS and PS. In recipe A the share of sustainable polymers is slightly above 70 % by wt. and in recipe B around 85 %. 80 kg of each compound were produced on a twin screw extruder in the Siemens technical centre. At the BSH company (Bosch und Siemens Hausgeräte GmbH) the compounds were injection moulded on normal production ABS and PS moulds. The green ABS alternative was used to manufacture covers for vacuum cleaners and, using the green replacement for PS, transparent door holders for refrigerators were produced. These products are shown in the figures 1 and 2 and demonstrate in an impressive manner that by means of a product-oriented material development many applications can be realized with sustainable compounds based on biopolymers from renewable sources and CO 2 -polymers. www.siemens.com Table 1: Comparison of properties ABS recipe A. PS recipe B. shrinkage in flow dir. % 0.6 0.7 0.4 0.07 shrinkage vertical % 0.7 0.8 0.6 0.09 E-modulus, MPa 2300 2550 3300 3400 σy, MPa 39 35 46 58 εy, % 2.1 2.5 2 27 Izod Impact RT, kJ/m² 70 10 8 28 HDT / B, °C 97 105 82 51 density, g/cm³ 1.07 1.30 1.07 1.25 New ‘basics‘ book on bioplastics This new book, created and published by Polymedia Publisher, maker of bioplastics MAGAZINE is now available in English and German language. The book is intended to offer a rapid and uncomplicated introduction into the subject of bioplastics, and is aimed at all interested readers, in particular those who have not yet had the opportunity to dig deeply into the subject, such as students, those just joining this industry, and lay readers. It gives an introduction to plastics and bioplastics, explains which renewable resources can be used to produce bioplastics, what types of bioplastic exist, and which ones are already on the market. Further aspects, such as market development, the agricultural land required, and waste disposal, are also examined. An extensive index allows the reader to find specific aspects quickly, and is complemented by a comprehensive literature list and a guide to sources of additional information on the Internet. The author Michael Thielen is editor and publisher bioplastics MAGAZINE. He is a qualified machinery design engineer with a degree in plastics technology from the RWTH University in Aachen. He has written several books on the subject of blowmoulding technology and disseminated his knowledge of plastics in numerous presentations, seminars, guest lectures and teaching assignments. 110 pages full color, paperback ISBN 978-3-9814981-1-0: Bioplastics ISBN 978-3-9814981-0-3: Biokunststoffe Order now for € 18.65 or US-$ 25.00 (+ VAT where applicable, plus shipping and handling, ask for details) order at www.bioplasticsmagazine.de/books, by phone +49 2161 6884463 or by e-mail books@bioplasticsmagazine.com bioplastics MAGAZINE [05/12] Vol. 7 49
