Railway Sleepers from Mixed Plastic Waste- Railwaste Project Status Information as of Oct, 2010

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1 Railway Sleepers from Mixed Plastic Waste- Railwaste Project Status Information as of Oct, 2010 Coordinator Fraunhofer Institut für chemische Technologie (ICT) Joseph-von-Fraunhofer-Str. 7 D Pfinztal Project partners PAV GmbH & Co KG Großbeerenstraße 171a D Berlin Next Generation Recyclingmaschinen GmbH Gewerbepark 22 A-4101 Feldkirchen This project was supported by the Era-Net SUSPRISE by the Funding agencies: Germany: Projektträger Jülich for BMBF Zimmerstraße Berlin Austria: Forschungsförderungsgesellschaft (FFG) for bmvit Sensengasse Wien 1 Summary The goal of the RailWaste project was to show the feasibility of crosstie production based on secondary raw materials. As of today, the RailWaste R&D consortium has achieved the following results: Identification of a thermoplastic compound mixture based on mixed plastic waste which is technically capable of serving as a crosstie matrix. Development and implementation of a pilot scale process for continuous production of mixed plastic waste crossties. Production of a set of 2.6 m crossties for physical testing purposes. Thus the project goal has been reached fully. The next steps after completion of the project are the scale-up of the process, and to develop a business model. 1

2 2 Project goal and Scope From mid-2008 to February 2010, a consortium under the guidance of Fraunhofer ICT has been developing railway crossties from an alternative, renewable raw material. This material is mixed plastic waste (MPW), in order to increase secondary raw materials use, to improve materials efficiency along with preparation of a business case for railway sleepers from alternative materials. It was intended to produce railway sleepers from an intelligent combination of post consumer waste materials: Mixed plastic wastes (MPW) along with glass fibre wastes and auxiliary agents, to form a composite polymer crosstie. The overall goal was to show the feasibility of crosstie production based on secondary raw materials. In the materials R&D area, a compound from waste, additives, glass fibers was developed by Fraunhofer ICT (Pfinztal/Germany) to meet the mechanical requirements of sleepers. The material was supplied and pre-processed by PAV Recyclate (Berlin/Germany). NGR Recycling Machines (Feldkirchen/Austria) developed the processing equipment and technology, and actually produced the crossties on a pilot scale. The development work was carried out under the auspices of the German Susprise Secretariat Projektträgerschaft Jülich PTJ, Berlin Office. 2.1 Requirements The values required for mechanical stability of polymer sleepers were taken from several patents, summarized in Table 1. Table 1: Mechanical properties requirements Parameter Patent/Process Minimum Maximum PAV Tests assessment Youngs DE A Modulus in WO [] A Wo A good (Tietek) US B US A WO A Modulus (USPL) [] WO A1(Polywood) ok WO A1 to tension (UPS) improved [] be 2.2 Materials Selection Research yielded the identification of potential waste streams from post-consumer plastic packaging material. Major parameters for a pre-selection have been the thermoplastic content 2

3 of the materials, the composition, availability, and price. Different types of secondary glass fibers and of mixed plastic waste were chosen for the experiments. Several materials consisting of MPW were tested for the use in sleepers, in order to increase secondary raw materials use, and to improve materials efficiency along with preparation of a business case for railway sleepers from alternative materials. The MPW was combined with a reinforcement of glass fiber waste to improve mechanical stability and stiffness. A foaming agent was optionally tested to get a foamed core and to reduce the material consumption of the product. Series of experiments were carried out to identify the best composition of the final compound. For the glass fiber reinforcement, production waste material was selected for the reinforcement of the MPW. The compounds containing this material showed almost comparable properties like with the use of (primary) chopped strands. Compared to the requirement values given of existing patents (Table 1), equal or better values for the chosen materials were reached for the parameters Young s Modulus, Modulus, Tension and Impact. A selection of results is presented in Table 2. Table 2: Mechanical properties of selected MPW compounds Modulus Tension Youngs Modulus Charpy Impact kj/m2 Heat Deflection Temperature (HDT) C MPW Mixture , ,5 69,2 MPW Mixture , ,4 65,3 MPW Mixture , ,2 73,7 2.3 Production Technology For the experimental production process a single screw extruder with several dosing units and a vacuum degassing unit was developed (Figure 1). The output of the extruder is kg/h. The calibration works under backpressure and the profile is cooled with sprinkling water. The dimensions of the cross-section of profile are 24 x 26 cm. It was decided to choose an extrusion process instead of an intrusion process which is used e.g. by Reluma because this allows a continuous process management and a constant compound quality. Scale-up of the process to a higher sleeper output is not subject to the current RailWaste project. 2.4 Pilot Sleeper Production By the end of 2009 a series of sleeper sections up to approx. 1 m length made from different material mixtures and two full-length (2.6 m; Figure 2) sleepers had been produced. The production process ran stable, and the products did neither show bending nor remarkable shrinkage during cooling. The best extrusion results were obtained with a material which consists mostly of HDPE and a minor percentage of PP. The homogeneity of the profiles was first checked thermographically during the cooling phase. Lateron, this result was verified by cutting the profile. For product testing purposes, a set of 3 full scale sleepers was produced in January 2010 and sent to an external testing facility for physical testing. Results of these tests are expected to be available in March

4 Figure 1: Profile section of the test plant set up at NGR (Austria) Figure 2: Full Scale Mixed Plastic Waste sleeper of RailWaste consortium Figure 3 shows a cut profile using the fiber reinforced MPW material. In Figure 3a it can be seen that cavities appear solely in the core, reducing the weight of the sleeper without altering the mechanical properties of the sleeper. Figure 3b shows the size of cavities which was assessed to be not critical in terms of minimization of the stability of the sleepers. a) b) Figure 3: Quarter of profile fiber reinforced MPW material (a), Cavities close-up (b) 4

5 2.5 Sleeper tests The sleepers produced were sent to HTW Dresden where several tests were performed. These included: - Determination of the force needed to pull out a screw - Bending test at the rail fastening device (3-point-test), static and dynamic (2 Mio changes of load) - Bending test at the middle of the sleeper (3-point-test), static and dynamic (2 Mio changes of load) The Railwaste-sleeper easily passed all tests. Furthermore, the sleepers were transported to the sleeper factory of the Deutsche Bahn AG at Schwandorf. There mounting and fastening tests were carried out with the polymer sleepers, such as drilling, cutting and shaping. The benchmark chosen were wood sleepers. The results obtained were very positive, as the polymer sleeper may be processed with the same equipment as wood sleepers. Moreover, it can be expected that at least one process for sleeper production will become unnecessary with the polymer sleepers, thus resulting in less cost and shorter production time. 2.6 Contact Data For further information on the project, please refer to Dr.-Ing. Gudrun Gräbe Tel. +49(0) 721/ gudrun.graebe@ict.fraunhofer.de Dr.-Ing. Jörg Woidasky Tel. +49(0) 721/ joerg.woidasky@ict.fraunhofer.de Fraunhofer-Institut für Chemische Technologie Joseph-von-Fraunhofer-Str. 7 D Pfinztal (Berghausen) 5